International Workshop on Sorghum Stem Borers

Cover: Stem borer larval (Chilo partellus) damage on sorghum plant (above), and stem tunneling (below). International Workshop on Sorghum Stem Borers

17-20 Nov 1987 ICRISAT Center, India

ICRISAT International Crops Research Institute for the Semi-Arid Tropics Patancheru, Andhra Pradesh 502 324, India 1989 Citation: l C R l S A T ( I n t e r n a t i o n a l Crops Research Institute for the Semi-Arid Tropics) 1989. International W o r k s h o p on Sorghum Stem Borers, 17-20 N o v 1987, l C R I S A T Center, India. Patancheru, A . P . 502 324, India: I C R I S A T .

Conference Coordinators K.F.Nwanze S.L.Taneja

Technical Reviewers J.A.Wightman S . Z . M u k u r u

Scientific Editor K.F.Nwanze

Publication Editors S.Kearl V.Sadhana

I S B N 92-9066-145-3

The International Crops Research Institute for the Semi - A r i d T r o p i c s is a n o n p r o f i t , scientific, research and t raining institute receiving support from donors through the Consultative Group on International Agricultural Research. Donors t o I C R I S A T include governments and agencies o f A u s t r a l i a , B e l g i u m , C a n a d a , Federal Republic o f G e r m a n y , F i n l a n d , France, I n d i a , Italy, Japan, Netherlands, Norway, Sweden, Switzerland, United Kingdom, United States of America, and the foll o w i n g international and private organizations: Asian Developm ent Bank, Deutsche Gesellschaft fur Technische Zusamme n a r b e i t (GTZ), International Development Research Centre, Inter national Fund for Agricultural Development, The Europea n E c o n o m i c C o m m u n i t y , The Opec F u n d f o r I n t e r n a t i o n a l D e v e lopment, The World Bank, and United Nations Developmen t Programme. Information and conclusions in this publicat ion do not necessarily reflect the position of the aforementioned governments, agencies, and international and private organizations.

T h e o p i n i o n s in this publication are those of the authors and not necessarily those of ICRISAT. The designations employed and the presentation o f the material i n this p u b l i c a t i o n d o n o t i m p l y the expression o f any o p i n i o n whatsoever o n the p a r t o f I C R I S A T concerning the legal status of any c o u n t r y , t e r r i t o r y , city, or area, or of its authorities, or concerning the d e l i m i t a t i o n of its frontiers or boundaries. W h e r e trade names are used this does n o t constitute endorsement of or d i s c r i m i n a t i o n against any p r o d u c t by the Institute. Contents

Inaugural Session

L.D.Swindale. Welcome Address 3

J.M.J.de Wet. Introduction 6

K.F.Nwanzer. Purpose and Objectives 7

K.M.Harris: Keynote Address: Recent Advances in S o r g h u m and Pearl M i l l e t Stem Borer Research 9

Regional Reports

R.D.Chundurwar. S o r g h u m Stem Borers in I n d i a and Southeast Asia 19

,O.Ajayr. S o r g h u m Stem Borers in West A f r i c a 27

K. V. Seshu Reddy. S o r g h u m Stem Borers in Eastern A f r i c a 33

S.Z.Sitholer. S o r g h u m Stem Borers in Southern A f r i c a 41

R.Reyes: S o r g h u m Stem Borers in Central and S o u t h A m e r i c a 49

Discussion 59

Bionomics and Control (except Host-plant Resistance)

K.M.Harris: Bioecology of S o r g h u m Stem Borers 63

Prem Kishore. Chemical C o n t r o l of Stem Borers 73

A.N. Verma and S.P.Singh: C u l t u r a l C o n t r o l of S o r g h u m Stem Borers 81

M.Betbeder-Matibet Biological C o n t r o l of S o r g h u m Stem Borers 89

S.L. Taneja and K.F.Nwanzer. Assessment of Yield Loss of S o r g h u m and Pearl M i l l e t due to Stem Borer Damage 95

K.F.Nwanze and R.A.E.Mueller. Management Options of S o r g h u m Stem Borers f o r Farmers in the S e m i - A r i d Tropics 105

Discussion 115

Host-plant Resistance

B.R. Wiseman: Methodologies Used f o r Screening f o r Resistance t o Fall A r m y w o r m i n S o r g h u m 119

K.Leuschner. A Review of S o r g h u m Stem Borer Screening Procedures 129

S.L. Taneja and S. Woodhead. Mechanisms of Stem Borer Resistance i n S o r g h u m 137 M.J.Lukefahr. Considerations in the Development of a Host-plant Resistance P r o g r a m Against the Pearl M i l l e t Stem Borer 145

Discussion 150

Breeding for Resistance

M.B.Kalode, J.S.Bentur, and T.ESrinivasan: Screening and Breeding Rice f o r Stem Borer Resistance 153

B.L.Agrawal and S.L. Taneja: Breeding f o r Resistance to Stem Borer ( C h i l o partellus Swinhoe) in S o r g h u m 159

W.D.Guthrie: Breeding Maize and Sorghum for Resistance to the European C o r n Borer 169

Discussion 176

Plenary Session

Recommendations 179

Discussion 182

Participants 185 Inaugural Session

Welcome Address

L.D. Swindale1

G o o d m o r n i n g , ladies and gentlemen. It is my pleasure to welcome y o u to this International W o r k s h o p on Sorghum Stem Borers. Some of yo u have been here before and have spent various lengths of time w i t h us. It is my pleasure to welcome old colleagues and to those of y o u for w h o m this is a first visit to I C R I S A T , I extend a special welcome. I hope that y o u w i l l take this o p p o r t u n i t y to learn about I C R I S A T and what we do here, besides sorghum and stem borer research. I am pleased to note that y o u w i l l have a half day field t r i p to see I C R I S A T field w o r k and I hope that y o u w i l l take the o p p o r t u n i t y to see what else is going on here at I C R I S A T Center. It has been raining a lot f o r the last few days, the climate is rather nice and c o o l , but the rains have come very late this year and generous at somewhat the w r o n g time. D u r i n g the m a i n rainy season we had very little rain and crops have suffered badly. Crops that are in the field, particularly those that are mature, show evidence of grain weathering and m o l d . This applies to some of the crops that have been left to stand beyond the n o r m a l harvesting date for y o u people to see. I hope y o u w i l l keep this in m i n d as y o u t o u r the fields, that these crops have been left standing to accomodate your visit and do not represent I C R I S A T ' s n o r m a l crop management practices. S o r g h u m is a very i m p o r t a n t crop in the diets of millions of people, particularly in Asia and A f r i c a where over 9 0 % of the sorghum produced is used for human f o o d . But it is also important in other parts of the w o r l d , particularly in the Americas. S o r g h u m is one of I C R I S A T ' s five mandate crops, the others being pearl millet, pigeonpea, chickpea, and groundnuts. We have a geographic mandate area, the semi-arid tropics, hence the name I C R I S A T , the International Crops Research Institute f o r the S e m i - A r i d Tropics. As you k n o w , the crops I have mentioned, particularly sorghum, pearl millet, pigeonpea, and groundnuts are crops of the semi-arid tropical regions, so to that extent our crops mandate and our geographic mandate converge very well. Research on sorghum started in 1972 w i t h the establishment of ICRISAT Center, and sorghum insect pest research at I C R I S A T Center was initiated t w o years later in 1974. We concentrate on four major groups of insects: shoot fly, midge, stem borers, and head bugs. Because this w o r k s h o p is dealing particularly w i t h stem borers, let me say a few words about this group of insects. Here in I n d i a , at I C R I S A T Center, we concentrate on the spotted stem borer Chilo partellus. In eastern and southern A f r i c a , research also concentrates on this stem borer. In West A f r i c a , the maize stalk borer, BusseoJa fusca, is of primary concern. The severity of stem borer damage can result in severe loss of crop stand when seedlings are attacked, or in the case of later infestations, stem tunneling, which weakens the stem and results in stem breakage and unfilled grains. Losses caused by stem borers have been reported to be between 5 - 1 5 % in West A f r i c a , and 18-27% in East A f r i c a . In India, reported losses range as high as 5 5 - 8 3 % on certain susceptible hybrids and varieties, although I am sure that this is not a n o r m a l occurrence. If we did n o t h i n g to minimize these losses, w i t h all the other insect pests and various biotic and abiotic yield reducers, it w o u l d be very difficult for farmers to grow good crops, particularly for small farmers of the semi-arid tropics, which constitute our m a i n target group. It is extremely i m p o r t a n t that our research, and I w o u l d suggest, your research, be aimed at increasing the output of this important grain. Increasing yield per unit of cost is the most i m p o r t a n t way in w h i c h we can help the p o o r people of the S A T and of the w o r l d , the people

1. Director General, International Crops Research Institute for the Semi-Arid Tropics (ICR1SAT), Patancheru, A.P. 502 324, India.

3 w h o depend u p o n this type of c o m m o d i t y f o r their livelihood. By reducing the impact of yield reducers we are d o i n g just that. It is true we can c o n t r o l these pests w i t h insecticides. But chemical control of stem borers is not practical in subsistence agriculture or w i t h this low cost crop in general. Adjustment and initiation of other practices appears to hold more promise. Cultural practices, manipulation of planting dates, crop rotations, and intercropping can all help to avoid pest damage. So w i l l the use of parasites and predators, although these have not proved particularly successful in stem borer control. That is why at I C R I S A T , we emphasize host-plant resistance (HPR), hoping to put as m u c h technology i n t o the seed and then transfer that seed to small farmers in the most efficaceous way. H P R is economic, efficient and a long-term approach to be used, either alone or in combination w i t h other methods in an integrated pest management system. F r o m the initial identification of the m a j o r borer species of importance in sorghum in the 1970s, we have moved closer towards p r o v i d i n g the component parts for the management of this pest. These are: • O u r field research on resistance to stem borers is conducted in I n d i a at Hisar under natural infestation and at ICRISAT Center under artificial infestation. • Resistance screening techniques have been standardized and are also being used at various other locations. • We have so far screened 18 600 entries in the germplasm collection and have identified 70 resistant sources, some of which are being used in our breeding program. • Ovipositional nonpreference and antibiosis are the major mechanisms of resistance to Chilo, and we have identified various sorghum genotypes w i t h different resistance factors. • We have a new and m o d e r n insect-rearing laboratory at I C R I S A T Center w h i c h has greatly facilitated the screening and selection processes of large quantities of germplasm and breeding materials, as well as a l l o w i n g us to conduct specific studies on insect-pest/ host- plant interactions. • Emphasis has also shifted to our A f r i c a n programs. I C R I S A T entomologists are now based in Z i m b a b w e and Niger where the focus is also on borers. We expect to have an entomologist based in K a n o , Nigeria, in early 1988 and another one probably supplied by I R A T in B a m a k o , M a l i as well. Dr de Wet and his colleagues w i l l tell you what strategies are used in our breeding p r o g r a m for stem borer resistance. O b t a i n i n g high levels of resistance to stem borer is difficult. E n t o m o l o - gists are able to produce levels of artificial infestation in the field that virtually no cultivar of sorghum is able to stand up to. Yet, even under very high levels of infestation, we can find entries that sustain less than 25% seedling damage in the f o r m of deadhearts. N o w I wonder if y o u need to do more than that. D u r i n g the course of this meeting I w o u l d like y o u to consider whether we really need to try to get resistance higher than 2 5 % deadheart. If we can have that level of tolerance under high levels of infestation then perhaps we have accomplished what we really need to accomplish in host-plant resistance. I w o u l d like to acknowledge the presence of representatives f r o m various organizations w i t h w h o m we collaborate in stem borer research, including the Overseas Development Natural Resources Institute ( O D N R I ) , the International Centre of Insect Physiology and Ecology ( I C I P E ) , the A l l I n d i a Coordinated S o r g h u m Improvement Programme (AICSIP), and Haryana Agricultural University (HAU). I am also pleased to note the presence of delegates f r o m the United States Department of Agriculture ( U S D A ) , the Institut de recherches agronomiques tropicales et des cultures vivrieres ( I R A T ) , the C ommonwealth Agricultural Bureau International (CABI); and National Programs from several African countries, India, and Central America. Y o u have set aside half a day to review not only y o u r recommendations and discussions but y o u r programs of w o r k . I am really keen that y o u should give us the benefit of your advice and counsel on I C R I S A T ' s sorghum stem borer research and what y o u t h i n k it should be. At present we are in a very active planning stage preparing f o r a new five-year p r o g r a m of w o r k . This is a very good time f o r y o u to give us your advice on what we should do f o r y o u . We see our efforts as

4 part of a dynamic overall system, where changes of c o n d i t i o n and changes in research emphasis are essential to keep us vital. W i t h that, I wish you all a successful workshop. Before I pass on to the next speaker, I wish to pay homage to a d y n a m i c statesman. President Kountche of Niger was a foremost and most concerned citizen of his country w h o put the well-being of the Sahelian farmers and increased agricultural p r o d u c t i o n as the p r i o r i t y of his priorities. Under his leadership, ICRISAT received full support and encouragement for our activities at the Sahelian Center. I remember d u r i n g my visit with him in August 1985, he emphasized that we should increase not only cereal production in Niger but more importantly, maximize productivity. I ask you all to stand up and j o i n me in one minute of silence.

5 Introduction

J.M.J. de Wet1

Welcome to the Cereals P r o g r a m , and particularly the entomology research unit wh i c h has organized this workshop. I hope your stay at I C R 1 S A T w i l l be pleasant and productive, and that y o u w i l l f i n d the time to visit w i t h scientists of other research units, not only in cereals, but also the Legumes and Resource Management Programs. The Cereals Program has research projects in breeding, pathology, entomology, physiology, and microbiology. Research is stra• tegic and applied in nature, and designed to produce a useful end-product that may be a screening technique, new breeding line, or some basic i n f o r m a t i o n required to improve effi• ciency of our crop improvement programs at I C R I S A T Center, Africa, Central America, M e x i c o , and Caribbean. D u r i n g the last fifteen years the E n t o m o l o g y U n i t has been successful in developing reliable screening techniques for resistance to the important insect pests of sorghum and pearl millet. This allowed breeders to identify genotypes of these cereals w i t h various degrees of resistance or at least tolerance to sorghum midge, shoot fly, and stem borer. Indeed, a sorghum cultivar resistant to midge, and bred by I C R I S A T was released for cultivation in India. Breeding for resistance to shoot fly and stem borer are receiving special attention at ICRISAT Center at this time. I n t r o d u c i n g traits that confer resistance to these pests into elite breeding lines, however, has proved to be difficult. This is not surprising. Resistance seems to be conditioned by several genes that may be distributed across the chromosome complement of sorghum. This workshop was organized by the Entomology Unit to review the research endeavors in the Cereals P r o g r a m on stem borer, and to advise on future research directions. In particular, the program w o u l d like answers to t w o basic questions. One is whether stem borer on sorghum is of sufficient economic importance in A f r i c a and Asia to justify further research on control methods. Assuming that the answer is yes, the second question is whether breeding for resistance, chemical control, biological control, agronomic practices, or a combination of these deserves further research. Should the choice include breeding, the program w o u l d like to have y o u r o p i n i o n on the chances of successfully converting an elite breeding line w i t h fair tolerance to stem borer to a cultivar w i t h true resistance to this insect. The question is, whether such a complex genetic resistance system can be introduced into a highly productive cultivar w i t h o u t upsetting its balanced genetic system. The Cereals Program is l o o k i n g f o r w a r d to your recommendations. I can assure you that they w i l l be considered carefully in planning future research on stem borer control. The Cereals Program has manpower and other resources to solve the stem borer problem if it is solvable. We only wish to be sure that we do not invest resources on a research problem that does not warrant high p r i o r i t y , or in research that has a high probability of failure. I wish y o u success in your discussions during the next several days.

1. Program Director, Cereals Program, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, A.P. 502 324, India.

6 Purpose and Objectives

K. F. Nwanze1

Ladies and gentlemen, let me add my bit of welcome to y o u all to this w o r k s h o p . The International W o r k s h o p on S o r g h u m Stem Borers is a f o l l o w - u p to the International S o r g h u m E n t o m o l o g y W o r k s h o p held in July 1984 at Texas A & M University, College Station, Texas, U S A . Some of y o u were present at that w o r k s h o p w h i ch set the stage f o r subsequent ones on insect pests of sorghum. Thus, I hope the present w o r k s h o p is, in a way the first in a series of workshops that will deal w i t h specific groups of insect pests of sorghum. W h y a w o r k s h o p on sorghum stem borers? Let me answer this question w i t h others. W h y is Bueseola fusca devastating in one year and not in others? W h y is Chilo partellus a severe pest in East A f r i c a and not in West Africa? W h y are Chilo partellus populations very high in Hisar and very low in Patancheru? W h y are natural enemies of stem borers not efficient in controlling stem borers? W h a t are the actual losses caused by stem borers in farmers' fields? If stem borer damage results in yield losses, what is the economic threshold level? W h y is stem tunneling not often correlated w i t h yield? W h a t yield factors are more i m p o r t a n t in stem borer resistance: dead hearts? Stem tunneling? Peduncle damage? Head chaffiness? Do we need higher levels of stem borer resistance, that is, less than 2 0 % deadhearts? To what extent is current research on sorghum stem borer c o n t r o l of relevance to the farmers of the semi-arid tropics (SAT)? W h a t are farmers' perceptions of losses due to stem borer damage? The list of questions continues ad i n f i n i t u m . We probably have the answers to some of these questions but I doubt if anyone present here knows all the answers to them. Thus, to bring together entomologists and breeders f r o m across continents, to draw on the advances that have been made on other cereal crops (maize and rice), and to compare notes f r o m other regions, constitutes an attempt at answering the many questions that still remain unanswered. At I C R I S A T we recognize host-plant resistance as a major component in pest management strategies. We also emphasize the need to understand particular pest situations and the biology of the pests, not as an end in itself but as it relates to the crop in particular agroecosystems. We have organized the sessions in such a way that due attention is given to all these aspects. But more i m p o r t a n t l y , we have provided ample time for discussion after each session, as well as time slots for g r o u p discussions and a plenary session, where I hope we w i l l w o r k in concert to identify areas of collaboration, prioritize research objectives, and provide insights into how we can properly manage sorghum stem borers in the S A T . A l l this is being optimistic, but l oo ki n g at the caliber of scientists gathered here today, I am confident that we w i l l come away f r o m this w o r k s h o p satisfied w i t h the efforts that each of us has contributed in m a k i n g it a success. T h a n k y o u .

1. Principal Cereals Entomologist, Sorghum Group, Cereals Program, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, A.P. 502 324, India.

Recent Advances in Sorghum and Pearl Millet Stem Borer Research

K.M. Harris1

Abstract

Information on sorghum and pearl millet stem borer research published since 1980 is reviewed, and important advances in knowledge of the biology, ecology, and control of the main pest species of Chilo, Coniesta, Diatraea, Sesamia, Busseola and some other relevant genera of Lepidoptera are summarized. Progress in the assessment of crop losses, the production of resistant varieties, implementation of biological control, and the development of other nonchem- ical methods of pest management are assessed and requirements for further research and development are identified.

Introduction • monitor the possible development of biotypes.

Research on the lepidopterous stem borer pests of sorghum was reviewed on a world basis at the Inter- Crop Loss Assessment national Sorghum Entomology W o r k s h o p at Texas A & M University in July 1984 ( I C R 1 S A T 1985) and • Improve yield loss assessment methods; relevant papers presented at that meeting are referred • obtain quantitative data on yield losses attrib- to later in this review. At the conclusion of the utable to pests; and Workshop, general recommendations for future • develop methods to establish economic injury w o r k on sorghum entomology were made and are levels for important pests. paraphrased below.

Plant Breeding Surveys • Intensify collection and exchange of insect-resis- • Conduct surveys regularly in major sorghum tant germplasm; growing areas to assess pest situations; and • extend screening programs;

1. Director, Commonwealth Agricultural Bureau International (CAB1), Institute of Entomology, 56 Queen's Gate, London. SW7 5JR, UK. l C R l S A T (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, l C R l S A T Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

9 • study insect/ host relationships and insect behav- w o r k on the main stem borer species are therefore ior in greater detail to improve control strategies; intended to provide an i n t r o d u c t i o n to the more • identify and study resistance mechanisms; detailed consideration of current w o r k w h i c h w i l l be • study the inheritance of resistance; and the main purpose of this W o r k s h o p . • intensify plant breeding for insect-resistant/ stable-yielding varieties and hybrids.

Chilo partellus ( S w i n h o e ) Cultural Control This is the most i m p o r t a n t lepidopterous stem borer • Study traditional control practices; and attacking sorghum, maize, and millet in the Indian • emphasize the importance of crop d u r a t i o n , subcontinent and East Africa. In recent years more p l a n t i n g dates, crop hygiene, and other agro- research has been done on this pest than on any nomic practices in reducing pest incidence. other species of sorghum stem borer. Most of that research has been based in India, especially at I C R I - S A T and at Indian Agricultural Research Institutes and Universities, and in Kenya at the International B i o l o g i c a l C o n t r o l Centre of Insect Physiology and Ecology ( I C l P E ) . particularly at the M b i t a Point Field Station. D u r - • Identify natural enemy complexes of sorghum ing the period 1980-87 at least 50 research papers insect pests and determine their efficiency; relating mainly to this species on sorghum or maize • study factors influencing the biology, ecology, have been published, including contributions to the and behavior of key natural enemies in cropping Proceedings of the International Study Workshop systems; on Crop-Borers and Emerging Strategies for their • develop simple strategies to favor natural ene- C o n t r o l , held at the M b i t a Point Field Station, mies; and Kenya, 14 18 June 1982 (Insect Science and its • determine the effectiveness of exotic natural A p p l i c a t i o n , Special Issue, vol.4, nos. 1 and 2); the enemies, especially for use against stem borers. Proceedings of the International Sorghum Ento- mology Workshop, College Station, Texas, 15-21 July 1984 ( I C R I S A T 1985) and the Proceedings of Chemical Control the International Study W o r k s h o p on Host Plant Resistance and its Significance in Pest Management, • Intensify research on the judicious use of insecti- held at I C I P E , N a i r o b i , 10-15 June, 1984 (Insect cides; Science and its A p p l i c a t i o n , Special Issue, vol.6, • discourage prophylactic use of insecticides; and No.3). Some of the key papers are noted below and • develop recommendations for insecticide use. fuller bibliographies are available in the Sorghum and Millets I n f o r m a t i o n Centre, Bibliographies and Newsletter, in Sorghum and Millets Abstracts, in the Review of Applied Entomology, Series A (Agricul- Integrated Pest Management (IPM) tural), and in C A B International A n n o t a t e d Biblio- graphies. • Develop I P M strategies.

It is now appropriate to consider the advances Biology that have been made since that m a j o r meeting on sorghum entomology, and to consider the progress The biology of Chilo partellus has been studied over that has been made in sorghum stem borer research many years at various locations in I n d i a and East d u r i n g the 1980s. In the brief period of three years A f r i c a , and is well k n o w n . In recent years, Neupane since the 1984 W o r k s h o p , it is unlikely that many et al. (1985) have published the first detailed account major advances w i l l have been made and this review, of the bionomics of this species in Nepal; K h a n which is based on literature published between 1980 (1983) has studied its biology in Pakistan; Verma and 1987, w i l l inevitably fail to include recent, as yet and J o t w a n i (1983) compared the biology and unpublished w o r k . The f o l l o w i n g summaries of behavior of specimens collected from Delhi, Indore,

10 Nagpur, and Hyderabad, India; and Alghali (1985) (1970) that sorghum can produce a good crop and studied it in Kenya. Length of lifecycle, time of adult feed a large borer population but that compensatory emergence, ovipositing potential, location of egg g r o w t h f o l l o w i n g borer damage may be reduced dur- batches on plants, and incidence of larval diapause ing periods of stress. A l g h a l i (1986) assessed the vary appreciably between localities. These are possi- effects of cultivar, time of attack, and incidence of ble indicators of the existence of biotypes, and sea- infestation on two cultivars in experiments at Mbita sonal variability within localities, but the factors Point, Kenya. He concluded that the greatest yield determining these variations do not seem to have reductions (about 20-25% of control yields which been fully investigated. resulted when plants were artificially infested w i t h I m p o r t a n t research on the behavior of first-instar 5-20 first-instar larvae at six weeks after germina- larvae immediately after hatching, has been con- tion) may not necessarily warrant control, except tinued by C h a p m a n et al. (1983) and Bernays et al. when planting is staggered and the pest population is (1985) who have studied the survival and dispersal of high. His research also suggested that infestation y o u n g larvae and the mechanisms by which newly later than six weeks after germination may not result hatched larvae reach the leaf whorl from oviposition in significant losses of grain. The general consensus sites near the base of sorghum plants. seems to be that appreciable yield loss results mainly Ovipositional preferences of female moths on 70 f r o m attack w i t h i n the first t w o months of g r o w t h , different varieties and hybrids were studied by Singh especially from deadheart formation, and that exten- and Rana (1984) but the behavior of ovipositing sive stem tunneling during later g r o w t h does not females, which results in different egg counts on significantly depress yield, but further rigorous preferred and nonpreferred plants, was not recorded. investigation of crop losses caused by C. partellus seems desirable.

Ecology Chemical Control Few recent studies of C. partellus can be considered to be essentially ecological and there seems to be a Chemical control of stem borers on sorghum in general lack of rigorous studies of the population A f r i c a and Asia has never been either particularly dynamics of this pest. A short paper (Mahadevan appropriate or feasible. W i t h increasing costs of and Chelliah 1985a) reports the use of lighttraps to insecticide applications and increasing concern about m o n i t o r seasonal abundance in 1981 - 82 at one loca• environmental pollution, research on chemical con- tion in India, and two papers on the influence of trol is greatly reduced. Since 1984, only four papers weather on the seasonal occurrence of this species abstracted in the Review of Applied Entomology have also been published (Mahadevan and Chelliah (Series A) are directly concerned w i t h chemical con- 1985c, 1986). t r o l of C. partellus on sorghum: (1) K h a n (1983) reported that carbofuran and disulfoton, applied in the f u r r o w , were more effective than foliar applica- Crop Loss Assessments tions of nonsystemic compounds in Pakistan; (2) Sachan and Rathore (1983) reported a 126% yield There is still a notable absence of objective assess- increase in Uttar Pradesh, India, of sorghum pro- ments of sorghum yield losses directly attributable tected by a program of a soil application of 10% to C. partellus. In the period under review, Flattery phorate granules, followed by six applications of 4% (1982) published the results of field trials over five carbaryl granules to the leaf whorls and a spray years on grain sorghum in Botswana. He noted that application of carbaryl at flowering; (3) Kishore there was often an increase in yield when C. partellus (1984) compared the t i m i n g and scheduling of 4% damage resulted in increased tillering and that the endosulfan dust in India; and (4) Natarajan and inherent tillering ability of one of the cultivars used Chelliah (1986) reported effective control of C. par- in the trials (cv 65D) masked any yield reductions tellus with dust formulations of BHC, carbaryl, mal- that might have resulted f r o m attacks by this pest. athion, endosulfan and phenthoate, also in India. Some yield decreases were recorded f o l l o w i n g high The general conclusion, at least for India, has been levels of C. partellus attack but were not statistically succinctly stated by Leuschner et. al. (1985): "Insec- significant. These results were interpreted by the ticides should be used as a last resort and only where author as supporting the view expressed by Doggett absolutely necessary".

11 Plant Breeding Biological Control

Screening f o r resistance a n d , to a lesser extent, Gilstrap (1985) predicted excellent prospects for the investigations of the mechanisms of resistance, have biocontrol of C. partellus and of other stem borers, been the main recent research activities on C. partel- b o t h by the conservation of endemic natural enemies lus. Leuschner et. al. (1985) reviewed the role of and by the i n t r o d u c t i o n of exotic agents, but there host-plant resistance in pest management in India are few signs of progress being made in this direction and concluded that, with a strong breeding effort, on sorghum. present levels of resistance to this and o t h e r key Inayatullah (1983) studied host selection by the pests c o u l d be developed to play an i m p o r t a n t braconid parasite Apanteles flavipes (Cameron) and role i n the i m p l e m e n t a t i o n o f I P M i n s o r g h u m reported that it was especially attracted to frass pro- and that l o w levels of stem b o r e r resistance c o u l d duced by C. partellus and other borers feeding on be s u p p l e m e n t e d w i t h c u l t u r a l and c h e m i c a l mea- sorghum and maize. Host-plant associations may be sures. T h e techniques used to mass rear C. p a r t e l - of particular importance to parasitic Hymenoptera lus on a r t i f i c i a l diets, to establish infestations on and Diptera and merit more detailed study. s o r g h u m plants and to evaluate resistance have C h a k r o v a r t y et al. (1983) studied the effects of the been summarized by Taneja and Leuschner (1985). bacterium Serratia marcescens Bizio, applied as an They emphasized that deadheart formation causes aqueous cell suspension, w h i c h prevented egg hatch m a x i m u m g r a i n yield loss and s h o u l d be given and killed first-instar larvae. This and other patho- greatest weight in e v a l u a t i n g resistance. T h e y also gens also merit more research. noted t h a t a n t i b i o s i s and tolerance are the m a i n resistance mechanisms. Teetes (1985) assessed the role of insect-resistant Cultural Control sorghums in pest management, and Srivastava(1985) summarized the results of screening programs up to Seshu Reddy (1985) reviewed the main cultural the early 1980s in India and described a breeding practices that are used against sorghum stem borers, scheme to strengthen stem borer resistance in sor- including: tillage and m u l c h i n g ; time of planting; g h u m . Rana et al. (1985) reviewed i n f o r m a t i o n on spacing; fertilizer and water management; crop sani- stable resistance sources, resistance mechanisms, tation; removal of deadhearts, volunteer plants, and and the genetics of resistance. They concluded that alternative host plants; crop rotation; and inter- antibiotic mechanisms are more i m p o r t a n t for stem cropping. borer resistance than ovipositional nonpreference. Intercropping has received most recent attention A detailed laboratory study of the influence of f r o m research workers. M a h a d e v a n and Chelliah varietal resistance on oviposition and larval devel- (1985b), studied the effects of intercropping sorghum opment by Singh and Rana (1984) showed that anti- w i t h various leguminous crops to c o n t r o l C. partel- biosis, measured in 70 sorghum cultivars, was ex- lus and reported that intercropping w i t h cowpea or pressed as slower larval development, higher larval lablab reduced stem borer infestation and increased m o r t a l i t y and lower pupal weights, and that factors grain and straw yields. O m o l o and Seshu Reddy affecting larval development exist independently in (1985) reported the results of intercropping experi- leaf and stem tissues. They compared the results of ments in Kenya which indicated that sorghum- their laboratory experiments with field observations cowpea i n t e r c r o p p i n g reduced the incidence of on the same cultivars and showed that larval dura- C. partellus and other borers. M o r e research is t i o n and larval mortality on leaf w h o r l tissues were needed but much i n f o r m a t i o n is already available negatively and significantly correlated w i t h b o t h the and could be used by extension workers to advise percentage of deadhearts and the number of tunnels farmers and to develop I P M programs. per plant and per stalk. Oviposition in cages was positively and significantly correlated w i t h the percentage of deadhearts and the number of cavities per plant and per stalk. These studies emphasize the Coniesta ignefusalis ( H a m p s o n ) importance of successful larval establishment in the leaf w h o r l of young sorghum plants as the main This pyralid species is closely related to C. partellus factor determining deadheart f o r m a t i o n and conse- and occupies a similar niche in West A f r i c a . It is quent grain yield loss. mainly a pest of pearl millet but also attacks

12 s o r g h u m in the drier areas of the Sahel. Nwanze it has probably been associated w i t h cultivated (1985) commented on C. ignefusalis'm the context of sorghum since the earliest origin of the crop in pest management in pearl millet in the Sahel but A f r i c a . A l t h o u g h it is a widespread and i m p o r t a n t relatively little research has been done on it. Some pest, little detailed research has been done on this progress has been made w i t h biological and other species in recent years. Adesiyun (1983) studied the studies d u r i n g the United States Agency f o r Interna- effects of intercropping sorghum, maize, and millet t i o n a l Development ( U S A I D ) / F o o d and A g r i c u l - in Nigeria and concluded that the almost total inabil- ture Organization of the United Nations ( F A O ) / ity of B. fusca females to oviposit effectively on C o m i t e permanent interetats de lutte contre la millet resulted in reduced infestations of sorghum secheresse dans le Sahel (CILSS)/IPM Project. when intercropped w i t h millet, which is a c o m m o n practice in the drier areas of West Africa. Gebreki- dan (1985) recorded that nearly 6000 indigenous E t h i o p i a n sorghums were evaluated in a natural 'hot Diatraea saccharalis (Fabricius) spot' infestation of B. fusca but less than 1 % showed tolerance. This species also belongs to the family Pyralidae and Most recently, van Rensberg et al. (1987) have is therefore relatively closely related to Chilo and published a detailed account of the ecology of Coniesta. It occurs in tropical and subtropical areas B. fusca on maize in South A f r i c a . The results of this of the U S A , the Caribbean, Central and South w o r k are partly relevant to research on sorghum and A m e r i c a and mainly attacks sugarcane, maize, and are referred to in a later paper presented at this sorghum. I n f o r m a t i o n on its biology and ecology is W o r k s h o p (Harris 1989). reviewed in Harris (1989). It is therefore the Western hemisphere equivalent of C. partellusand C. ignefusalis w i t h biological similarities which indicate that Sesamia cretica L e d e r e r research on all three species may be interrelated, especially in the contexts of biological control and in Temarak et al. (1984) have studied the interaction of selecting for resistance. M i h m ( 1985) reported meth- the braconid parasite, Bracon brevicornis Wesmael ods of artificial infestation and the evaluation of and its hyperparasite, Pediobius bruchida ( R o n - resistance in sorghum against this species and G u i - dani) w i t h overwintering populations of S. cretica in ragossian and M i h m (1985) reviewed progress made stacked sorghum stems in Egypt. Larval mortality in screening 200 sorghum lines d u r i n g a Centro rates of 14-68% were recorded, w i t h parasitism Internacional de M e j o r a m i e n t o de maiz y T r i g o accounting f o r 5-28%. By the end of the winter ( C I M M Y T ) / I C R I S A T cooperative p r o g r a m i n hyperparasitism by Pediobius had risen to 100%. M e x i c o . Some results of screening in Brazil have The only other recently published w o r k on this spe- also been reported (Boica et al. 1983; Boica and Lara cies seems to be that by Ba A n g o o d and Hubaishan 1983, and Lara and Perussi 1984). Tolerance is the (1983) reporting the screening of several introduced m a i n type of resistance detected in these studies w i t h high-yielding sorghum varieties in the Yemen D e m o - low levels of antibiosis and of ovipositional n o n - cratic Republic. The introduced D w a r f W h i t e M i l o preference. was very susceptible; the lower-yielding local variety van Leerdam et al. (1985) studied the host-finding Baini was less susceptible; and the o p t i m u m sowing behavior of the braconid parasite, Apanteles fla- dates for most varieties tested were 26 August and 16 vipes (Cameron) and f o u n d that a water soluble September. substance present in fresh D. saccharalis frass was attractive to female parasites searching f o r hosts. These observations parallel those made on the same parasite on C. partelIus in Pakistan (lnayatullah O t h e r Sesamia Species 1983). A l t h o u g h other species of Sesamia have been recorded as stem borers of sorghum ( H a r r i s 1985; Busseola fusca ( F u l l e r ) Seshu Reddy 1985) little research is being done on them, indicating that they are generally considered This is the most i m p o r t a n t noctuid stem borer of less importance than the m a i n stem borer species attacking sorghum in A f r i c a south of the Sahara and dealt w i t h above.

13 Eldana saccharins W a l k e r d i s r u p t i o n w o u l d be on rice, maize, and sugarcane g r o w n as plantation crops. In the past this has been considered a relatively Finally, we do n o w have a better understanding of unimportant pest in Africa, except on sugarcane. the effects of stem borers on sorghum grain yields But Seshu Reddy (1985) noted that it has recently but t r u l y objective assessments of crop losses are still increased in importance on sugarcane, maize, and relatively rare and, in their absence, there may still sorghum in several areas of A f r i c a south of the be cases where subjective assessments overestimate Sahara, and it is the most i m p o r t a n t stem borer of pest status, especially d u r i n g the later stages of crop s o r g h u m in B u r u n d i . Sampson and K u m a r (1985) development. published an account of its biology and ecology on sugarcane in G h a n a and A t k i n s o n (1980) published a detailed account of its biology, distribution, and R e f e r e n c e s host plants in S o u t h Africa. Adesiyun, A . A . 1983. Some effects of intercropping of sorghum, millet and maize on infestation by lepidopterous stalk-borers, particularly Busseola fusca. Insect Science Conclusions and its Application 4(1-2):387-391. Alghali, A.M. 1985. Insect-host plant relationships. The D u r i n g the 1980s, progress has been made towards spotted stalk-borer, Chilo partellus ( S w i n h o e ) ( L e p i d o p - mainly empirical solutions of stem borer problems tera: Pyralidae) and its principal host, sorghum. Insect by selecting for host-plant resistance and incorporat- Science and its A p p l i c a t i o n 6:315-322.

ing resistance into higher-yielding varieties. Screen- Alghali, A.M. 1986. Effects of cultivar, time and amount of ing techniques, especially f o r Chilo partellus and Chilo partellus Swinhoe (Lepidoptera: Pyralidae) infesta• Diatraea saccharalis, are well established and could tion on sorghum yield components in Kenya. Tropical Pest easily be adapted f o r other species. Management 32:126-129.

The mechanisms of resistance have not been fully Atkison, P.R. 1980. On the b i o l o g y , d i s t r i b u t i o n and n a t u • researched, although some progress has been made ral host-plants of Eldana saccharina W a l k e r ( L e p i d o p • in studying the critical phase of establishment of tera: Pyralidae). Journal of the Entomological Society of first-instar larvae of C. partellus on young sorghum Southern Africa 43:171-194. plants. Other interactions between pest species and Ba-Angood, S.A., and Hubaishan, M.A. 1983. Effect of their host plants, b o t h in the adult and larval stages, sowing date and s o r g h u m cultivars on s n o o t i l y and stem merit f u r t h e r research w h i c h could provide the basis borers. Page 100 in Proceedings of the Tenth International f o r a better understanding of resistance. If resources Congress of Plant Protection, 20-25 Nov 1983, Brighton, were adequate, w h i c h they are not at present in UK. Vol.1. Croydon, UK: British Crop Protection either Asia or A f r i c a , studies of borer species on C o u n c i l .

their original grass hosts might also provide the basis Bernays, E.A, Woodhead, S.,and Haines, L. 1985. C l i m b • f o r further advances in plant breeding. ing by newly hatched larvae of the spotted stalk borer Chilo Some w o r k on chemical control continues and partellus to the top of sorghum plants. Entomologia Expe- may be of use in some special circumstances but rimentalis et Applicata 39:73-79. seems u n l i k e l y t o p r o v i d e feasible l o n g - t e r m Boica Junior, A.L., Zanini, J.R., and Moraes, M.L.T. solutions. 1983. Evaluation of grain and sweet sorghum genotypes C u l t u r a l methods of l i m i t i n g borer damage are w i t h regard to infestation w i t h Diatraea saccharalis(Fab., available but are seldom used effectively in areas 1794) ( L e p i d o p t e r a , Pyralidae. ( I n Pt., S u m m a r y in En.) where f a r m i n g communities lack the support of ade- Cientifica 11(1): 107-111. quate advisory services. Boica Junior, A . L . , and L a r a , F . M . 1983. E v a l u a t i o n of Biological control, which offers some possibilities s o r g h u m b i c o l o r ( L . ) M o e n c h genotypes resistance to Dia• of effective long-term control, will require substan- traea saccharalis (Fabricius, 1794) (Lepidoptera- tial research and implementation inputs if it is to be Pyralidae) and study of the mechanisms involved. (In Pt., successful. I n g r a m (1983) reviewed the position and Summary in En.). Anais da Sociedade Entomolgica do suggested further w o r k . Brasil 12:261-272.

C a m p i o n and Nesbitt (1983) have reviewed the Campion, D.G., and Nesbitt, B.F. 1983. T h e utilisation of use of pheromones f o r stem borer control and con- sex pheromones for the control of stem borers. Insect cluded that the m a i n potential f o r c o n t r o l by m a t i n g Science and its A p p l i c a t i o n 4 ( 1 - 2 ) : 191-197.

14 Chakravorty, B.P., Kundu, G.G., Hegde, S.V., and K h a n , B . M . 1983. Studies o n the b i o l o g y a n d c o n t r o l o f Sharma, J.K. 1983. Effect of Serratia marcescens Bizio f o r maize stem borer in Peshawar. Bulletin of Zoology the c o n t r o l of s o r g h u m stem borer, Chilo partellus ( S w i n - 1:51-56. hoe). I n d i a n J o u r n a l o f E n t o m o l o g y 45:456-458. Kishore, P. 1984. Timing and schedule of application of Chapman, R . F . , Woodhead, S., and Bernays, E.A. 1983. endosulfan to c o n t r o l s o r g h u m stem borer. I n d i a n J o u r n a l S u r v i v a l and dispersal of y o u n g larvae of Chilo partellus of A g r i c u l t u r a l Sciences 54(5):415-417. ( S w i n h o e ) ( L e p i d o p t e r a : Pyralidae) i n t w o cultivars o f Lara, M.F., and Perussi, E.M. 1984. Resistencia de sorgo sorghum. Bulletin of Entomological Research 73:65-74. sacarino Sorghum bicolor ( L . ) M o e n c h so ataque de Dia- Doggett, H. 1970. Sorghum. London:Longmans. 403 pp. traea saccharalis (Fabricius 1794). ( I n Pt.) Ciencia e C u l - tura 36:280-286. Flattery, K.E. 1982. An assessment of pest damage of grain sorghum in Botswana. Experimental Agriculture Leuschner, K., Taneja, S.L., and Sharma, H.C. 1985. T h e 18(3):319-328. role of host-plant resistance in pest management in sorghum in India. Insect Science and its Application Gebrekidan, B. 1985. Breeding s o r g h u m f o r resistance to 6:453-460. insects in eastern A f r i c a . Insect Science and its A p p l i c a t i o n 6:351-357. Mahadevan, N.R., and Chelliah, S. 1985a. Population dynamics of the s o r g h u m stem borer, Chilo partellus Gilstrap, F.E. 1985. Concepts f o r biological c o n t r o l of (Swinhoe), in light trap. Pages 104-106 in Behavioral and arthropods attacking sorghum. Pages 403-412 in Proceed- physiological approaches in pest management (Regupathy, ings o f the I n t e r n a t i o n a l S o r g h u m E n t o m o l o g y W o r k s h o p , A., and Jayaraj, S., eds.). Coimbatore, Tamil Nadu, I n d i a : 15-21 Jul 1984, College Station, Texas, USA. Patancheru, Tamil Nadu Agricultural University. A . P . 502 324, I n d i a : I n t e r n a t i o n a l C r o p s Research Insti- tute f o r the S e m i - A r i d T r o p i c s . Mahadevan, N.R., and Chelliah, S. 1985b. Influence of intercropping legumes with sorghums on stem borer, Chilo Guiragossian, V . , and M i h m , J . A . 1985. Improving host- partellus (Swinhoe). Pages 189-190 in Behavioral and p h y - plant resistance to fall a r m y w o r m and sugarcane borer in siological approaches in pest management (Regupathy, A. , s o r g h u m . Pages 201-204 in Proceedings of the Interna- and Jayaraj, S., eds.). Coimbatore, Tamil Nadu, India : tional Sorghum Entomology Workshop, 15-21 Jul 1984, Tamil Nadu Agricultural University. College Station, Texas, USA. Patancheru, A.P. 502 324, India: I n t e r n a t i o n a l C r o p s Research Institute f o r the S e m i - Mahadevan, N . R . , and Chelliah, S. 1985c. Influence of A r i d T r o p i c s . weather factors on seasonal occurrence of the s o r g h u m stem borer, Chilo partellus (Swinhoe). Pages 191-193 in Harris, K . M . 1985. Lepidopterous stem borers of s o r g h u m . Behavioural and physiological approaches in pest manage- Pages 161-167 in Proceedings of the International ment (Regupathy, A., and Jayaraj, S., eds.). Coimba t o r e , Sorghum Entomology Workshop, 15-21 Jul 1984, College T a m i l N a d u , I n d i a : T a m i l N a d u A g r i c u l t u r a l University. Station, Texas, USA. Patancheru, A.P. 502 324, India: I n t e r n a t i o n a l C r o p s Research Institute f o r the S e m i - A r i d Mahadevan, N.R., and Chelliah, S. 1986. Influence of T r o p i c s . season and weather factors on the occurrence of the s o r g h u m stem borer Chilo partellus ( S w i n h o e ) in T a m i l Harris, K . M . 1989. Bioecology of s o r g h u m stem borers. Nadu. Tropical Pest Management 32(3):212-2I4. Pages 63-71 in Proceedings of the I n t e r n a t i o n a l W o r k - shop of S o r g h u m Stem Borers, 17-20 N o v e m b e r 1987, Mihm, J.A. 1985. Methods of artificial infestation with ICRISAT Center, Patancheru, A.P. 502 324, India: Inter- Diatraea species and evaluation of stem borer resistance in national Crops Research Institute for the Semi-Arid s o r g h u m . Pages 169-173 in Proceedings of the Interna- T r o p i c s . tional Sorghum Entomology Workshop, 15-21 Jul 1984, College Station, Texas, USA. Patancheru, A.P. 502 324, ICRISAT (International Crops Research Institute for the India: International Crops Research Institute for the S e m i - Semi-Arid Tropics). 1985. Proceedings of the International Arid Tropics. Sorghum Entomology Workshop, 15-21 Jul 1984, College Station, Texas, USA. Patancheru, A.P. 502 324, India: Natarajan, K., and Chelliah, S. 1986. Chemical c o n t r o l of I C R I S A T . 4 3 4 p p . shootfly and stem borer of sorghum. Pesticides 20:23-24.

Inayatullah, C. 1983. Host selection of Apanteles flavipes Neupane, F.P., Coppel, H.C, and Chapman, R.K. 1985. (Cameron) (Hymenoptera: Braconidae): influence of host Bionomics of the maize borer, Chilo partellus Swinhoe, in and host plant. J o u r n a l o f E c o n o m i c E n t o m o l o g y Nepal. Insect Science and its Application 6:547-553. 76:1086-1087. Nwanze, K.F. 1985. S o r g h u m insect pests in West A f r i c a . Ingram, W . R . 1983. Biological control of graminaceous Pages 37-43 in Proceedings of the International Sorghum stem borers and legume pod-borers. Insect Science and its Entomology Workshop, 15-21 Jul 1984, College Station, Application 4:(1-2)205-209. Texas, USA. Patancheru, A.P. 502 324, India: Interna- tional Crops Research Institute for the Semi-Arid Trop i c s .

15 O m o t o , E.O., and Seshu Reddy, K . V . 1985. Effects of Temerak, S.A., Morsy, M.A., and Abdel-Galil, F.A. 1984. different sorghum based cropping systems on insect pests Notes on relative impact of Bracon brevicornis W e s m . a n d in K e n y a . Pages 395-401 in Proceedings of the Interna- its h y p e r p a r a s i t o i d , Pediobius bruchida ( R o n d a n i ) tional Sorghum Entomology Workshop, 15-21 Jul 1984, through populations of the hibernating larvae of the p i n k College Station, Texas, USA. Patancheru, A.P. 502 324, borer, Sesamia cretica Lederer in stacked s o r g h u m stalks I n d i a : I n t e r n a t i o n a l C r o p s Research Institute f o r the S e m i - (Hymenoptera: Braconidae, Eulophidae) (Lepidoptera: A r i d T r o p i c s . Noctuidae). Bulletin de la Societe Entomologique d'Egypte 63:213-218. R a n a , B.S., Singh, B . U . , and R a o , N . G . P . 1985. Breeding f o r shoot fly a n d stem borer resistance in s o r g h u m . Pages van Leerdam, M.B., Smith, J.W., and Fuchs, T.W. 1985. 347-360 in Proceedings of the International Sorghum Frass mediated, host-finding behavior of Cotesia flavipes, Entomology Workshop, 15-21 Jul 1984, College Station, a braconid parasite of Diatraea saccharalis (Lepidoptera: Texas, U S A . Patancheru, A . P . 502 324, I n d i a : I n t e r n a - Pyralidae). Annals of the Entomological Society of Am e r - tional Crops Research Institute for the Semi-Arid Tropi c s . ica 78:647-650.

Sachan, G . C . , and Rathore, Y . S . 1983. Studies on the van Rensberg, J.B.J., Walters, M.C., and Giliomee, J.H . complete p r o t e c t i o n of s o r g h u m c r o p against insect pests 1987. Ecology of the maize stalk borer, Busseola fusca by chemicals a n d thuricide at various stages of c r o p (Fuller) (Lepidoptera, Noctuida). Bulletin of Entomol o g - g r o w t h . Pesticides 17(6): 15-16. ical Research 77:255-269.

Sampson, M . A . , and K u m a r , R. 1985. Life history, devel- Verma, K.K., and Jotwani, M.G. 1983. L i f e processes of o p m e n t and behaviour of Eldana saccharina W a l k e r on the s o r g h u m stem borer Chilo partellus Swinhoe of differ- sugarcane in southern G h a n a . Insect Science a n d its A p p l i - ent agroclimatic areas. Indian Journal of Entomology c a t i o n 6:135-143. 45:477-478.

Seshu Reddy, K . V . 1985. Integrated approach to the con- t r o l of s o r g h u m stem borers. Pages 205-215 in Proceedings o f the I n t e r n a t i o n a l S o r g h u m E n t o m o l o g y W o r k s h o p , 15-21 J u l 1984, College S t a t i o n , Texas, U S A . P a t a n c h e r u , A . P . 502 324, I n d i a : I n t e r n a t i o n a l C r o p s Research I n s t i - tute f o r the S e m i - A r i d T r o p i c s .

Singh, B . U . , and R a n a , B.S. 1984. Influence of varietal resistance on oviposition and larval development of stalk borer Chilo partellus Swin., and its relationship to field resistance in s o r g h u m . Insect Science a n d its A p p l i c a t i o n 5:287-296.

Srivastava, K.P. 1985. Screening f o r s o r g h u m stem borer resistance. Pages 189-200 in Proceedings of the Interna- tional Sorghum Entomology Workshop, 15-21 Jul 1984, College Station, Texas, USA. Patancheru, A.P. 502 324, India: International Crops Research Institute for the S e m i - A r i d T r o p i c s .

Teetes, G . L . 1985. Insect resistant sorghums in pest m a n - agement. Insect Science and its Application 6:443-451.

16 Regional Reports

Sorghum Stem Borers in India and Southeast Asia

R.D. Chundurwar1

Abstract

Information on the distribution, bioecology, and host plants of sorghum stem borers is reviewed. The sorghum stem borer species recorded in India and Southeast Asia, their avoidable losses, and control tactics are discussed, together with their natural enemies including pathogens. Their potential for use in the control of stem borers is discussed.

Introduction central part of Thailand, sorghum is grown on marginal areas, or planted as a second crop after maize Of the 19.22 m i l l i o n ha of sorghum g r o w n t h r o u g h • for export to J a p a n , Saudi A r a b i a , and S o u t h out Asia, I n d i a accounts for 15.30 m i l l i o n ha w i t h a Korea. Very little sorghum is g r o w n in Indonesia or total p r o d u c t i o n of 10.30 m i l l i o n tonnes ( F A O any of the other Southeast Asian countries and very 1985). At the beginning of the century, I n d i a n little sorghum research has been done in those c o u n - sorghum yields averaged 498 kg ha-1. Production tries (Meksongsee and Chawanapong 1985). averages increased to 673 kg ha- 1 by 1985 mainly due I m p o r t a n t stem borers in different sorghum grow- to the i n t r o d u c t i o n of hybrids and improved v a r i • ing regions in I n d i a have been reviewed (Seshu eties in various states. R e d d y a n d Davies 1978,Gahukarand J o t w a n i 1980, S o r g h u m is an i m p o r t a n t grain and fodder crop of Srivastava 1985, and Sharma 1985). A review of India. A p p r o x i m a t e l y 9 0 % of the country's sorghum w o r l d literature on lepidopterous stem borer listed is g r o w n in the states of A n d h r a Pradesh, Gujarat, 46 species of borers on different crops (Jepson 1954). Karnataka, Madhya Pradesh, Maharashtra, Rajas- Other valuable research on these borers include the t h a n , and T a m i l N a d u . S o r g h u m grain is p r i m a r i l y area of systematics (Kapur 1950, 1967, Tarns and used as h u m a n f o o d in r u r a l areas, while stems and Bowden 1953, and Blesznski and Collins 1962), and leaves provide fodder for cattle. biology, injury, and control tactics (Ingram 1958, In Southeast Asia, sorghum is g r o w n in Bangla• Nye 1960, Harris 1962, 1985, Young 1970, and desh, Burma, Indonesia, Sri Lanka, Taiwan, Thai• Y o u n g and Teetes 1977). land, and the Philippines. In Bangladesh, sorghum is The major stem borer species associated with cultivated as a relay, m i x e d , or border crop, and sorghum in India and Southeast Asia have been rarely g r o w n as a m o n o c r o p . S o r g h u m is rapidly compiled (Table 1) f r o m C A B A n n o t e d B i b i l i o g r a - gaining p o p u l a r i t y in the Philippines as an economi• phies, E-105 issued by C o m m o n w e a l t h Institute of cal feed supplement for poultry and cattle. In the Entomology (1973-83). The following documents

1. Senior Scientist, Microbial Control Scheme (PL-480), Department of Entomology, Marathwada Agricultural University, Parbhani 431 402, Maharashtra, India.

I C R l S A T (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, I C R I S A T Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

19 various stem borer complexes f o u n d t h r o u g h o u t Damage and Extent of Losses I n d i a and Southeast Asia, w i t h attention to species distribution, occurrence, host plants, damage and In India, incidence of stemborers ranges f r o m 10-75% extent of crop losses, c o n t r o l tactics, and natural w i t h severe infestations that can necessitate resow- enemies. ing of the crop ( R a h m a n 1944, Trehan and Butani

Table 1. Sorghum stem borers, their distribution and hosts in India and Southeast Asia1 .

S t e m borer Distribution Host plants

A. Pyralidae Chilo partellus ( S w i n h o e ) Andhra Pradesh, Assam, Bihar, Delhi, Gujarat, Sorghum, maize, millet. Himachal Pradesh, Karnataka, Maharashtra, rice, sugarcane, bajra Orissa, Punjab, Rajasthan, and West Bengal sudan grass, ragi, Johnson States of India; Indonesia, Srilanka, grass. Job's tear, and Thailand. and K a w d i a ( C I E M a p , 184)

Chilo infuscatellus (Snellen) Andhra Pradesh, Assam (Shillong) Bengal, Bihar, Sugarcane, millet, Coimbatore, Delhi, Gujarat, Kerala, Madhya s o r g h u m , and rice Pradesh, Maharashtra, Mysore, Orissa, Rajasthan, Tripura, and Uttar Pradesh States of India.

Indonesia (Java), Korea, the Philippines, Taiwan, Thailand, and (South) Vietnam. ( C I E M a p 301)

Chilo auricilius ( D u d g e o n ) Andhra Pradesh, Assam, Bihar, Darjeeling, Sugarcane, rice. Delhi, Gujarat, Himachal Pradesh, Madhya and sorghum Pradesh, Maharashtra, Mysore, Orissa, Punjab, Rajasthan, and Tamil Nadu States of India.

Malaysia, the Philippines, Taiwan, Thailand, a n d V i e t n a m . ( C I E M a p 300)

Chilo sacchariphagus Indonesia, Malaysia, and People's S o r g h u m and (Bojer) (= Proceras Republic o f C h i n a sugarcane venosatus W a l k e r ) ( C I E m a p 177)

Maliarpha sopartella R o g o n o t I n d i a ( L u d h i a n a ) Rice and sorghum

Ostrinia furnacalis Guenee Assam, Bihar, Manipur, Mysore, Punjab, Maize, millet, and a n d West Bengal States of I n d i a . m a n y grasses

Indonesia, Korea, Malaysia, Srilanka, Taiwan, Thailand, and Vietnam. ( C I E m a p 294) B. Noctuidae Sesamia inferens ( W a l k e r ) Andhra Pradesh, Bihar, Madhya Pradesh, Sorghum, maize, millet, Maharashtra, Mysore, Orissa, Punjab, Uttar sugarcane, and grasses Pradesh, and West Bengal States of India.

Indonesia, Japan, Korea, the Philippines, Srilanka, Taiwan, and Thailand. ( C I E m a p 237)

1 . S o u r c e : C o m m o n w e a l t h I n s t i t u t e o f E n t o m o l o g y ( C I E ) , D i s t r i b u t i o n M a p s o f Pests, 56, Queen's G a t e , L o n d o n , E n g l a n d .

2 0 1949, and Pradhan and Prasad 1955). Overall losses stalks and stubble of sorghum ( R a h m a n 1944, due to stem borers may average 5 - 1 0 % in different Rawat 1967, Singh et al. 1975, C h u n d u r w a r 1978, regions in I n d i a for early-sown sorghum. Avoidable and Taley and T h a k r e 1980). The metamorphosis of losses w i t h the C S H 1 h y b r i d and the variety Swarna moths f r o m pupae has been reported to occur f r o m have been estimated to be 5 5 - 8 3 % ( J o t w a n i et al. the beginning of A p r i l to June in northern India 1971, and J o t w a n i and Y o u n g 1972). ( R a h m a n 1944, Trehan and Butani 1949, Panwar Stem borer severity on sorghum has ranged f r o m and Sarup 1979, and Singh et al. 1985). In M a h a - 5 4 - 1 0 0 % in different years over the last decade. rashtra, emergence of adults was observed in June or Damage of 6 0 - 7 0 % has been reported in Rajasthan, July, but emergence started at Gwalior at the end of for b o t h the C S H l hybrid and local varieties. It February and continued through the end of A p r i l . ranged f r o m 80-100% in Coimbatore, Dewas, Indore, Environmental conditions, primarily rainfall, deter- Mansoor, Nagpur, Ratlam, Sehore, and Udaipur mines the time of emergence of adults. districts. Besides these cases, peduncle damage has The biology and behavioral response of larvae been reported f r o m M a d h y a Pradesh on C S H 5, and have been studied in the laboratory. In a comparison severe infestations were reported on late sown of larvae collected from Delhi, Hyderabad, Indore, sorghum in K a r n a t a k a and early sown sorghum in and Nagpur, the larval population f r o m Delhi laid Gujarat ( A l C S I P 1975-87). more eggs and completed life cycles quicker than the Trials conducted at Hisar on plots under intensive others. In addition, 91.8% of larvae f r o m Delhi protection compared with nonprotected plots, have underwent diapause (Verma and Jotwani 1985). shown high yields in protected plots and very low yields in nonprotected plots. Infestation ranged f r o m 50-100% under field conditions (Taneja et al. 1987). Chilo infuscatellus Snellen, and Chilo auricilius (Dudg)

M a j o r S t e m B o r e r Species These t w o species of pyralids are primarily of economic importance to sugarcane and of minor impor- Chilo partellus ( S w i n h o e ) tance to sorghum. Both have been reported on sorghum in India, Indonesia, the Philippines, Tai- The species C. partellus, k n o w n as the spotted stem wan, and Thailand'. C. infuscatellus has been col- borer, is distributed in Bangladesh, India, Indone- lected in M a d h y a Pradesh, in central India, on maize sia, Sri L a n k a , and the Philippines. It is a major pest and sorghum hybrids. The biology and nature of of sorghum, maize, and sugarcane. C. partellus has damage are similar to C. partellus. The borer C. been recorded on other host plants, including Sudan auricilius is primarily a pest of rice, commonly grass (Sorghum vulgare), Nachini (Eleusinae cora- k n o w n as the gold-fringed rice borer. caua), Baru Johnson grass (Sorghum halepense). Jobs tears (Coix Lachryma J o b i L), and Burger (Polytoca harbata) (Trehan and Butani 1949). The Chilo sacchariphagus ( B o j e r ) borer is f o u n d throughout the Indian subcontinent and is a more serious pest in northern and central This species occurs in China, Indonesia, and Malay- regions. sia and is primarily a pest of sugarcane. It is k n o w n Population dynamics and seasonal abundance as the spotted borer. It is an important pest of studies at Coimbatore have revealed that adult activ- sorghum in Hopei province of China. The first- ity is higher in January than in other months, with instar larva is a leaf-feeder, concentrated in the plant highest damage on the crop sown d u r i n g M a r c h and w h o r l and the second-instar and the older larvae lowest on the crop sown in June or October ( M a h a - tunnel in the stem. There are two generations per devan and Chelliah 1986). In Maharashtra, the year. Peak oviposition occurs in mid-June for the number of larvae were found to be higher in winter first generation and in mid-August for the second sorghum than in rainy season sorghum. But the generation. C. sacchariphagus damage in spring average number of pupae, percentage of stem tun- sorghum has been reported at 65% and in summer neling, and percentage of internodes attacked, were sorghum at 35%. Losses reported from borer dam- highest in rainy season sorghum. age are 32% for spring sorghum and 8% for summer M a n y scientists reported C. partellus carryover in sorghum.

21 Maliarpha separatella (Ragonot) winter or d r y season. On hatching, larvae may pene- trate the stem directly and can k i l l the y o u n g plant. T h e species, k n o w n as the green striped borer, is The f u l l - g r o w n larva measures 25-30 mm in length reported to be a m a j o r pest of rice in A f r i c a . The and is pale yellow w i t h a p i n k tinge and a reddish- larvae were first observed in L u d h i a n a , I n d i a in the b r o w n head. Several larvae may be present in one stubble and lower stems of the C S H 1 sorghum gallery. P u p a t i o n takes place inside the tunneled h y b r i d . The biology and behavior of the pest has stem. The life cycle f r o m egg to adult is completed in been reported by Sandhu and C h a n d r a (1975). 46 days in summer and 71 days in winter. F o u r - t o - T h e adult m o t h is stout, measuring about 20-25 six generations are recorded per year in south I n d i a . m m , w i t h p r o m i n e n t dark red bands on the fore- Symptoms of damage are similar to those caused by wings, especially on adult females. Eggs are laid in C. partellus. batches and are yellowish-white and oval. The larvae e x h i b i t sexual d i m o r p h i s m . The male larvae have five violet-to-reddish stripes while females have Insect C o n t r o l a n d R e l a t e d R e s e a r c h f a i n t l y defined stripes or none at all. The larval period lasts f o r 6-9 days in the laboratory. Pupation C h e m i c a l C o n t r o l occurs in stems or stubble and lasts f o r 14-16 days. An average of one larva per stubble was recorded in In I n d i a , considerable w o r k has been done on chem- the field. ical control of C. partellus at the D i v i s i o n of Ento- mol og y ( I A R I , N ew D e l h i ) , b y the A l l I n d i a C o o r - dinated Sorghum Improvement Project (AICSIP), Ostrinia furnacalis (Guenee) and at various agricultural universities. In early trials, insecticides such as BHC and D D T applied as T h e species is k n o w n as the tropical corn borer and is sprays and dusts, proved effective in controlling distributed in parts of China, India, Korea, Malay- stem borers on local sorghums. Later spray formula- sia, Sri L a n k a , T a i w a n , T h a i l a n d , and Vietnam. tions of insecticides such as p a r a t h i o n , diazinon, T h i s species was first reported in T h a i l a n d as trichlorphos, carbaryl, malathion, and endosulfan O. salentialis (Snellen). It is an i m p o r t a n t pest of have proven effective in reducing the pest (Sukhani maize in T h a i l a n d and the Philippines, but infesta• 1986). The effectiveness of granular insecticides was t i o n on s o r g h u m is rarely observed. Succulent vari- tested f o r carbofuran 3%, chlorfenviphos 2%, and eties of sorghum have been found susceptible to this fensulfothion 5%, applied at 8, 10, and 12 kg per ha-1 species in T h a i l a n d . in leaf whorls (Vibhute et al. 1973-74, and Srivas- tava and Jotwani 1976). Other chemical controls were tested on high-yielding varieties and hybrids of Sesamia inferens (Walker) sorghum, such as endosulfan ( K u n d u and Sharma 1974), phorate and chlorfenviphos, mephosfolan T h i s species occurs in B u r m a , China, I n d i a , Indone- aldicarb, quinalphos, disulfoton, and a mixture of sia, Malaysia, Sri Lanka, T a i w a n , and the Philip- lindane and carbaryl (Venugopal et al. 1977, Srivas- pines (Teetes et al. 1983). It is k n o w n to be a pest of tava and Jotwani 1979, Jotwani 1979, Kundu and sugarcane, maize, sorghum, rice, wheat, and finger Kishore 1980, and Patel and J o t w a n i 1982). Results millet (Jepson 1954). It has been reported attacking revealed that carbofuran and endosulfan granules s o r g h u m in the Philippines ( Y o u n g 1970). In T h a i - were the most effective of the insecticides tested at l a n d , is a pest of b o t h sugarcane and rice, but it has different locations. not been reported on sorghum (Meksongsee and Trials were also conducted at D e l h i , K a n p u r , C h a w a n a p o n g 1985). In India, it is m i n o r rice pest Parbhani, and Udaipur, on comparative effective- and causes considerable damage to maize ( K a p u r ness of proved granular and foliar sprays of different 1967). insecticides. Tested under the AICSIP program, the The detailed biology of S. inferens has been stud- granular insecticides proved superior when applied ied in finger millet by K r i s h n a m u r t i and Usman in whorls. (1952). The adult moths are straw colored. Female Insecticides such as endosulfan 4 % , carbaryl 5%, m o t h lays creamy white eggs in clusters between the lindane 0.65%, phenthoate 2%, applied as dusts at leaf sheath and stem of the plant. Eggs hatch in reduced dosages of 8-10 kg ha- 1 in the leaf whorls, about 7 days but hatching may be extended in a proved effective and economical (Sadakathulla 1981,

2 2 and J o t w a n i 1982). In China, application of granules priate control measures can be recommended at the containing 0.25% demeton gave 8 0 % control of appropriate time. Critical studies are needed on pest stripped borer C. sacchariphagus (Anonymous 1977). population and their natural enemies (including Very little w o r k has been done on chemical control parasites, predators, and pathogenic microbes), and of other species of borers on sorghum. behavioral response to different species of stem borer. Information on bioecology, occurrence, and pop• Biological Control ulation dynamics of borers is scanty in Southeast Asia and further w o r k is needed in the region. The A number of parasites and predators of stem borer research on biocontrol aspects in different ecological have been recorded by various scientists ( R a o 1964, regions has to be given p r i o r i t y along w i t h other S h a r m a et al. 1966, and J o t w a n i , et al. 1978). control tactics. Recently, a large number of parasitoids have been reported f r o m D h a r w a d . Considerable i n f o r m a t i o n is also available f r o m other parts of the w o r l d and R e f e r e n c e s reviewed by V a n Rensburg and van H a m b u r g (1975), and Greathead (1971). Anonymous 1977. Bionomics and control of striped sorghum borer, Procerus venosatus Walker. (In Ch. Sum• In I n d i a , attempts were made to c o n t r o l C. partel- m a r y in En.) A c t a E n t o m o l o g i c a Sinica 20:417-425. lus by releasing strains of egg parasite Tricho- gramma exiguum from Barbados, Colombia, and AICSIP (All India Coordinated Sorghum Improvement the Philippines in different ecological areas. The Project) 1975-87. Progress reports of the AH India C o o r d i • parasite has been established in Delhi and Nagpur nated Sorghum Improvement Project, Indian Council of Agricultural Research and Cooperative Agencies. New areas (Jotwani 1982). Recent releases of egg and D e l h i , I n d i a : A I C S I P larval parasites Trichogramma chilonis and Apan- teles flavipes have been successful, attacking C. par- Bleszynski, S., and Collins, R.J. 1962. A short catalogue of tellus in sorghum penduncle w i t h up to 65.5% m o r - the w o r l d species of f a m i l y C r a m b i d a e (Lepidoptera). A c t a tality ( A I C S I P 1986-87). Zoologica. Cracoviensia 7:197-389. A vast a m o u n t of literature is available on patho- Chundurwar, R.D. 1978. Population density of immature genic microbes, i.e. fungal, bacterial, and viral dis- stages of Chilo partellus ( S w i n h o e ) in s o r g h u m stubbles. eases of stem borers. R a m a k r i s h n a n and K u m a r Madras Agricultural Journal 65:553-554.

(1977) reviewed the w o r k done on pathogenic micro- Easwarmoorthy, S. and D a v i d , H. 1979. A granulosis virus bes in India. The fungus Fusarium aleyrodis proved of sugarcane shoot borer, Chilo infuscatellus Snell (Lepi- effective in controlling the stem borer when sprayed doptera: Crambidae). Current Science 48:685-686. either in spore suspension or crude t o x i n (Sinha and F A O 1985. FAO Production Yearbook, v.39. Rome, Italy: Prasad 1975). Similarly, the granulosis and nuclear F A O . 121pp. polyhedral virus of different strains were reported on C. infuscatellus, C. sacchariphagus, and 5. infer- Fletcher, T . B . 1914. Some S o u t h I n d i a n insects. M a d r a s , India: Government Press. 565 pp. ens in India (Easwarmoorthy and D a v i d 1979, Nayak and Srivastava 1979). Bacterial disease caused Gahukar, R.T., and Jotwani, M.G. 1980. Present status of by Serratia marascens has been recorded f r o m field pests of s o r g h u m and millets in India. T r o p i c a l Pest C. infuscatellus in sugarcane (Sithanatham 1979). Management 26:138-151.

A l t h o u g h useful i n f o r m a t i o n is available on parasi- Greathead, D. 1971. A review of biological c o n t r o l in E t h i • toids and insect microbes that attack the stem borer opian region. CIBC Technical Communication no.5. Farn- complex, a systematic use of these biotic agents has ham R o y a l , S l o u g h , U K : C o m m o n w e a l t h A g r i c u l t u r a l not been exploited. Bureaux. 162 pp.

Harris, K . M . 1962. Lepidopterous stemborers of cereals in C o n c l u s i o n Nigeria. Bulletin of Entomological Research 53:129-171. Harris, K . M . 1985. Lepidopterous stemborers of s o r g h u m . F r o m the present level of knowledge on the control Pages 161-167 in Proceedings of the International of stem borers, it is obvious that the damage caused S o r g h u m E n t o m o l o g y W o r k s h o p , 15-21 J u l 1984, College by this pest could be reduced in India, and in Sou- Station, Texas, USA. Patancheru, A.P. 502 324, India: theast Asia. Economic threshold levels for different International Crops Research Institute for the Semi-Ar i d stem borers should be investigated so that appro- Tropics.

23 Ingram, W . R . 1958. T h e lepidopterous stalk borers asso- Meksongsee, B., and Chawanapong, M. 1985. S o r g h u m ciated with Gramincae in Uganda. Bulletin of Entomologi - insect pests in Southeast Asia. Pages 57-64 in Proceedings cal Research 49:367-383. of the International Sorghum Entomology Workshop, 15-21 Jul 1984, College Station, Texas, USA. Patancheru, Jepson, W . F . 1954. A critical review of the world literature A.P. 502 324, India: International Crops Research Insti- on the lepidopterous stalk borers of tropical graminaceous tute for the Semi-Arid Tropics. crops. London, UK: Commonwealth Institute of Entomol- ogy. 127 p p . Nayak, P., and Srivastava, R . P . 1979. Nuclear p o l y h e d r o - sis on certain insect pests of rice. Current Science Jotwani, M . G . et al. 1978. Investigations on insect pests of 48:122-123. sorghum and millets with special reference to host plant resistance: f i n a l technical report (1972-77). lARl Research Nye, I.W.B. I960. T h e insect pests of graminaceous crops Bulletin (New Series) no.2. New Delhi, India: Indian Ag r i - in East Africa. Colonial Research Study no.31. London , cultural Research Institute. 116 p. U K : Her Majesty's Stationery Office. 48pp.

Jotwani, M . G . 1979. Increasing sorghum production by Panwar, V . P . S . , and Sarup, P. 1979. Response of maize chemical c o n t r o l of insect pests. Pesticides 13:56. varieties to Chilo partellus (Swinhoe) damage during off- season sowings. Journal of Entomological Research Jotwani, M . G . 1982. Factors reducing sorghum yields: 3:161 - 167. Insect pests. Pages 251-255 in Sorghum in the eighties: proceedings of the International Symposium on Sorghum, Patel, Z.R., and Jotwani, M.G. 1982. Efficacy and eco- 2 7 N o v 1981, l C R l S A T Center, India. V o l . 1 . Patancheru nomics of certain insecticides used for the control of A . P . 502 324, India: I n t e r n a t i o n a l Crops Research Insti- s o r g h u m shootfly Atherigona soccata (Rondani) and stem tute f o r the S e m i - A r i d T r o p i c s . borer Chilo partellus (Swinhoe). Entomon 7:387-395.

Jotwani, M . G . , and Young, W . R . 1972. Recent develop- Pradhan, S., and Prasad, S.K. 1955. Correlation between ments in chemical c o n t r o l of insect pests of s o r g h u m . Pages the degree of damage due to Chilo zonellus S w i n . and the 377-398 in Sorghum in seventies (Rao, N.G.P., and Hou- yield o f j o w a r g r a i n . I n d i a n J o u r n a l o f E n t o m o l o g y se.L.R., eds.). New D e l h i , India: O x f o r d and I B H Publish- 15:136-137. ing C o . R a h m a n , K.A. 1944. Biology and control of maize and Jotwani, M.G., Chandra, D., Young, W.R., Sukhani, j o w a r borer (Chilo zonellus Swin.). Indian Journal of Agri- T . R . , and Saxena, P . N . 1971. Estimation of avoidable cultural Science 14:303 307. losses caused by insect complex on s o r g h u m h y b r i d C S H - 1 Ramakrishnan, N.,and Kumar, S. 1977. Biological control and percentage increase in yield over treated control. of insects by pathogen and nematodes. Pesticides 32-47. Indian J o u r n a l of E n t o m o l o g y 33:375-383. R a o , V . M . 1964. Survey of n a t u r a l enemies of pests of Kapur, A . P . 1950. The identity of some Crambinae asso- paddy. Final report P-480 Project no. A 7-ENT-5. Banga- ciated w i t h sugarcane in India and certain species related to lore, Karnataka, India: Commonwealth Institute of Bio- them (Lepidoptera, Pyralidae). Proceedings of the Roya l logical C o n t r o l . E n t o m o l o g i c a l Society of L o n d o n , Series B 101:389-434. R a w a t , R.R. 1967. An estimation of population of Chilo Kapur, A . P . 1967. T a x o n o m y of the rice stem borers. zonellus Swinhoe in sorghum stubbles at Sehore (M.P.). Pages 1- 43 in The major insect pests of the rice plant: Indian Journal of Entomology 29:220-221. proceedings of a S y m p o s i u m , 14-18 Sep 1964, Los Banos, Laguna, Philippines. Baltimore, Maryland, USA: John Sadakathulla, S. 1981. Studies on control of stem borer H o p k i n s Press. and grain midge on sorghum. Pesticides 15(6):27 29.

Krishnamurti, B.,and Usman, S. 1952. The ragi stem borer Sandhu, G.S., and Chandra, R. 1975. Occurrence of green Sesamia inferens Walker. Bulletin of the Department of striped borer, Maliarpha separatella Ragnot on s o r g h u m A g r i c u l t u r e , M y s o r e State, E n t o m o l o g y Series N o . 15. in Punjab. Journal of the Bombay Natural History Society 72:872-873. K u n d u , G . G . , and Sharma, J.K. 1974. Note on chemical c o n t r o l of s o r g h u m stem borer. Indian J o u r n a l of A g r i c u l - Seshu Reddy, K.V., and Davies, J.C. 1978. Pests of t u r a l Sciences 44:902-903. sorghum and pearl millet, and their parasites and predators, recorded at I C R I S A T Center, I n d i a , up to December K u n d u , G . G . , and Kishore, P. 1980. Chemical control of 1977. Cereal Entomology Progress Report no.1. Patan- s o r g h u m stem borer, Chilo partellus (Swinhoe). I n d i a n cheru, A.P. 502 324, India: International Tropics. 20 pp J o u r n a l o f E n t o m o l o g y 42:791-793. (Limited distribution.) Mahadevan, N.R., and Chelliah, S. 1986. Influence of sea- Sharma, H . C . 1985. Strategies for pest c o n t r o l in s o r g h u m son a n d weather factors on the occurrence of the s o r g h u m in India. Tropical Pest Management 31:167-185. stem borer Chilo partellus (Swinhoe) in T a m i l N a d u . T r o p - ical Pest Management 32(2):212-214.

2 4 Sharma, A . K . , Saxena, J . D . , and R a o , B.R.S. 1966. A Trehan, K.N.,and Butani,D.K. 1949. Notes on life history, catalog of the hymenopterous and dipterous parasites of bionomics and control of Chilo zonellus (Swinhoe) in Chilo zonellus (Swinhoe) (Crambidae: Lepidoptera). Bombay Province. Indian Journal of Entomology I n d i a n J o u r n a l o f E n t o m o l o g y 28:510-542. 11:47-59.

Singh, B., Battu, G.S., D ha l i w a l , J.S., and A t w a l , A . S . V a n Rensburg, N.J., and van H a m b u r g , H. 1975. G r a i n 1975. P o p u l a t i o n studies on the maize borer Chilo parteIlus sorghum pests: an integrated control approach. Pages ( S w i n h o e ) in P u n j a b . I. M o d e of hybernation and survival 151 162 in Proceedings of the First Congress of the E n t o - o f o v e r - w i n t e r i n g larvae. I n d i a n J o u r n a l o f E n t o m o l o g y m o l o g i c a l Society of S o u t h e r n A f r i c a , 30 Sep 3 Oct 1974, 37(2): 132-136. Stellenbosch, South Africa (Durr, H.J.R., Giliomee, J.H ., and Neser, S., eds.). Pretoria, South Africa: Entomol o g i c a l Singh, U.C., M i s r a , U.S., Ohamdhere, S . V . , a n d Dwivedi, Society o f Southern A f r i c a . V . S . 1985. C a r r y o v e r of the s o r g h u m stalk borer Chilo partellus (Swinhoe) in off-season in different crops. Jour- Venugopal, M . S . , M a n i , M . , and Balasubramanian, M . nal of E n t o m o l o g i c a l Research 9:220-222. 1977. Comparative toxicity of certain granular insecticides to stem borer, Chilo partellus Swinhoe infesting s o r g h u m . Sinha,S.K.,and Prasad, S.M. 1975. A biological a p p r o a c h Indian Journal of Plant Protection 5:148-152. to the c o n t r o l of maize borer, Chilo zonellus (Swinhoe). C u r r e n t Science 44:197 198. Verma, K.K., and Jotwani, M.G. 1985. Life process of the s o r g h u m stem borer Chilo partellus (Swinhoe) of different Sithanantham, S. 1979. Occurrence of bacterial diseases on agroclimatic areas. Indian Journal of Entomology some sugarcane insects in I n d i a . I n d i a n J o u r n a l of Plant 45:477-478. Protection 2:211-212. Vibhute, K.S., Taley, Y.M., and Morey, G.D. 1973-74. Srivastava, K.P. 1985. S o r g h u m insect pests in I n d i a . Chemical control of sorghum shootfly, Atherigona sonata Pages 4 5 - 4 6 in Proceedings of the International Sorghum R o n d . and s o r g h u m stem borer, Chilo partellus (Zonellus) Entomology Workshop, 15-21 Jul 1984, College Station, (Swinhoe) o n h y b r i d C S H - 1 , Magazine, College o f A g r i - Texas, U S A . Patancheru, A . P . 502 324, India: Interna- culture, N a g p u r 46:6 10. t i o n a l Crops Research Institute f o r the S e m i - A r i d T r o p i c s . Young, W . R . 1970. Sorghum insects. Pages 235-287 in Srivastava, K.P., and Jotwani, M . G . 1976. Efficacy of sorghum production and utilization (Wall, J.S., and Ross, granular insecticides applied as w h o r l treatment f o r the W.M., eds.). Westport, Connecticut, USA: AVI Publish- c o n t r o l of sorghum stem borer Chilo partellus (Swinhoe). ing Co. Entomologists' Newsletter 6(8-9):50-52. Young, W.R., and Teetes, G.L. 1977. Sorghum entomol- Srivastava, K.P.,and Jotwani, M.G. 1979. Persistence and ogy. Annual Review of Entomology 22:193-218. residues of c a r b o f u r a n , disulfotan and endosulfan used f o r the c o n t r o l of m a j o r pests of s o r g h u m c r o p . J o u r n a l of Entomological Research 3:148-156.

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Taley, Y . M . , and Thakre, K . R . 1980. Note on the popula- t i o n dynamics in carryover of Chilo partellus (Swinhoe). I n d i a n J o u r n a l of A g r i c u l t u r a l Sciences 50:635-637.

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Taneja, S.L., Agrawal, B.L., and Henry, V . K . 1987. Host plant resistance to s o r g h u m stem borer. Presented at the A l l India C o o r d i n a t e d S o r g h u m I m p r o v e m e n t Project W o r k s h o p , 25-27 M a y 1987, M a r a t h w a d a A g r i c u l t u r a l University, Parbhani, Maharashtra, India.

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Stem Borers of Sorghum in West Africa with Emphasis on Nigeria

O. Ajayi1

Abstract

Lepidopterous stem borers are the main insect pests of sorghum in West Africa. Their relative importance, distribution, bioecology, and the damage they cause are described. The various control strategies that include cultural, genetic, biological, legislative, and chemical methods and the integration of these approaches into a pest management system are discussed. Recent changes in cropping patterns in the sorghum-growing areas of West Africa may have influenced the incidence levels and damage caused by stem borers. Future research needs are also indicated.

Introduction in Nigeria and other countries in the region although similar figures for other West African countries are S o r g h u m or Guinea corn, Sorghum bicolor ( L ) not readily available. M o e n c h , is the most widely cultivated cereal crop and the most i m p o r t a n t f o o d crop in the savanna areas of West Africa. Its importance can be illus• Species C o m p l e x trated w i t h the situation in Nigeria, the major p r o • ducer, where it accounts f o r about 5 0 % of the total Insect pests constitute an important factor limiting cereal p r o d u c t i o n and occupies about 4 6 % of the grain sorghum p r o d u c t i o n in West A f r i c a . The most total land area devoted to cereal p r o d u c t i o n (other important field insect pests are shoot flies, stem bo r • cereals are rice, maize, millet, and wheat). The area ers, head bugs, head caterpillars, and grain midges. devoted to sorghum is slightly more than 6 m i l l i o n Of these, the stem borers are the most i m p o r t a n t and ha and p r o d u c t i o n is estimated to be about 9 m i l l i o n most widespread. M u c h of the w o r k on the insect metric tonnes ( I A R 1984). These factors indicate pests of sorghum in the region has therefore been on that the crop w i l l continue to increase in importance stem borers.

1. Entomologist, Institute for Agricultural Research, Ahmadu Bello University, PMB 1044, Zaria, Nigeria.

I C R I S A T (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, I C R I S A T Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

27 Stem borers reported on sorghum in West A f r i c a tions t h r o u g h the dry season ( A b u 1986b) it is advis- include Busseola fusca (Fuller), Sesamia calamistis able to plow ratoons into the soil. H a m p s o n , Eldana saccharina Walker, S. poephaga For b o t h B. fusca and Sesamia, early planting has Tarns and Bowden, S. Penniseti T a r n s and Bowden, been f o u n d to lower stem borer infestation ( A b u and Acigona ignefusalis H a m p s o n . A. ignefusalis is 1986a). This probably explains why peasant farmers, p r i m a r i l y a pest of pearl millet, Pennisetum americ- w h o normally plant as soon as the rains become anum(L.) Leeke, but is a m i n o r pest of sorghum in a established, suffer less stem borer infestation than sorghum/millet intercrop. Although details vary occurs at experimental stations, where planting is between countries, B. fusca is the most important usually delayed. stem borer since it predominates in the major Another cultural control measure involves inter- sorghum-growing areas. Other species can be of cropping. Peasant farmers in West Africa almost p r i m a r y importance locally. F o r example, S. cala- invariably intercrop millet and sorghum. Available mistis predominates and E. saccharina is important information (Adesiyun 1983) indicates that inter- in the southern Guinea savanna in Nigeria ( A b u planting millet w i t h sorghum in alternate stands 1986a, b), while A. ignefusalis is more important w i t h i n the same r o w reduces larval infestation of n o r t h of latitude 11° 30'N in B u r k i n a Faso (Nwanze, B. fusca on sorghum, since the adults do not effec- ICRISAT, personal communication). The relative tively utilize millet for oviposition. importance and distribution of stem borers in West A f r i c a is strongly influenced by rainfall patterns. Resistant Varieties

In West A f r i c a , the use of insecticides is largely Control Measures beyond the means of the small farmer, and recommended chemicals are usually not available at the Cultural Control right time. Plant resistance is therefore an attractive method of reducing stem borer damage. The most logical cultural control measure against The search for stem borer resistant varieties in B. fusca, w h i c h spends the dry season in diapause, is Nigeria began in the early 1970s under the United to reduce the first generation adult population by States Agency for International Development k i l l i n g diapausing larvae w i t h i n the old stalks. This ( U S A I D ) JP 26 project. Hundreds of sorghum lines is best done by destroying old stalks by burning or f r o m the w o r l d collection were screened over a composting before the onset of the rains (Harris 4-year period at Samaru using natural infestation. 1962). Where the stalks are required for building, The entries were rated as R (resistant) if they had fencing, or firewood they should be partially burned; < 1 cm tunneling and evidence of larval mortality or the leaves should be burned a few days after the abandonment; I (intermediate) if tunneling was 1-10 heads have been removed, while the leaves are dry cm and there was evidence of larval mortality or but the stalks are not (Adesiyun and Ajayi 1980). abandonment; and S (susceptible) if the tunneling Heat generated f r o m burning leaves is sufficient to was > 10 cm and there was very little or no evidence k i l l the larvae w i t h i n the stalks. The stalks should be of larval mortality (IAR 1976). On this basis, 22 kept in the open rather than in large stacks in the varieties of the world collection and four improved shade of trees where larval survival is much higher. varieties were rated as resistant. Of the 22 varieties, Where the stalks are fed to animals, the residues and four were also reportedly resistant to shootfly (IS all unused stalks should be destroyed before the 6747, 6441,6449, and 8910). onset of the rains. In 1981 and 1982, MacFarlane (1984) screened For these cultural control measures to be effec• 122 entries f r o m I C R I S A T and the Institute for tive, they must be adopted by all farmers in the target Agricultural Research at Samaru, Nigeria. His para- area, otherwise, remaining insect populations will meters were percentage of stem tunneled, percentage continue to seek available hosts. One way to accom• internodes bored, and visual damage. Another set of plish this is to enlighten the farmers adequately or, if 122 entries f r o m an I C R I S A T project in Kamboinse, possible, enforce compliance by legislation. Burkina Faso, is currently being screened at Samaru. Sesamia can also be controlled by partial burning. A number of observations can be made f r o m these In the southern Guinea savanna, where sorghum attempts to find sources of resistance to stem borers ratoons support the carryover of Sesamia popula- in sorghum. One observation is that borer infesta-

28 t i o n is highly variable f r o m year-to-year, m a k i n g For the control of leaf-feeding stages of B. fusca interpretation of data difficult. Another is that the carbaryl 85 W P ; granular endosulfan 5 G ; and granu- a m o u n t of leaf feeding is not a reliable parameter f o r lar t r i c h l o r p h o n 5G applied into the w h o r l three measuring stem borer damage. This is probably times at weekly intervals have been recommended because m i x e d infestations of Sesamia and Busseola (Ajayi 1978, Adesiyun 1976). Granules of the sys- usually occur and only Busseola feeds on the leaves. temic insecticide carbofuran, applied into the plant- A l s o , there appears to be no correlation between ing hole at planting, followed by a side dressing 6 tunnel length and grain yield. weeks later, controls Sesamia and provides c o n t r o l It is clear that the methodology for evaluating of Busseola larvae which enter the stem at the base stem borer nurseries needs to be perfected, prefera- (IAR 1975, Ajayi 1987). Recent yield loss assessment bly using laboratory-reared larvae to artificially trials using insecticides show that stem borer con- infest nursery plants. To help accomplish this, an t r o l , in the southern Guinea savanna where Sesamia artificial diet was developed at Samaru composed of predominates, improved yields by 16-19% ( A b u wheat, soyabean flour, brewers yeast, ascorbic acid, 1986a). Similar stem borer c o n t r o l in the northern sorbic acid, formaldehyde, water, and agar. This diet Guinea savanna, where B. fusca predominates, yielded up to 6 0 % p u p a t i o n and adult emergence. improved yield by 4 9 % ( A j a y i 1987). In b o t h cases, Increasing the soybean flour content significantly the thick-stemmed sorghum variety SK 5912 was i m p r o v e d the rate of adult emergence ( A n o n y m o u s used. In trials at S a m a r u , in w h i c h several i m p r o v e d 1975). sorghum varieties were planted, the thin-stemmed varieties exhibited more severe damage than SK 5912 in terms of stem breakage, especially at the peduncle. It may be assumed, therefore, that stem Potential for Biological Control borers w i l l cause more yield reduction as more f a r m - ers adopt these improved, thin-stemmed varieties. Several parasitoids, predators, and disease organisms have been reported as natural enemies of sorghum stem borers in West A f r i c a (Harris 1962, G a h u k a r 1981). A c c o r d i n g to Harris, Tetrastichus Requisites for Integrated Control atriclavus, Apanteles sesamiae, and Pediobius furvus are always present on B. fusca towards the end of Various measures can be integrated and used in the g r o w i n g season and are probably its most i m p o r - c o n t r i b u t i o n to c o n t r o l stem borers. But there are a tant parasites. Bacillus thuringiensisand Aspergillus number of requisites before integration can be suc- spp are also f o u n d in or on the larvae and pupae of cessfully employed. Some of the more obvious and B. fusca at S a m a r u . The list of natural enemies w i l l pressing needs are listed below: probably increase as more efforts are made to search f o r them. A l t h o u g h the overall rate of parasitism of 1. In order to refine the use of insecticides, the eco- stem borers is low and seldom exceeds 10%, the use nomic threshold level f o r each stem borer species of natural enemies f o r biological control appears to and a complex of species needs to be determined. be w o r t h pursuing. Meanwhile, there have been no 2. To develop an effective biological control pro- studies on the p o p u l a t i o n , ecology and efficiency of gram, the biology, ecology, and efficiency of the these natural enemies, nor have local staff been ade- identified natural enemies of the stem borers need quately trained on their utilization. to be studied. 3. There is a need to develop an accurate procedure for breeding and screening sorghum lines f o r Chemical Control resistance to stem borers. Laboratory rearing and screenhouse facilities, which are currently not A l t h o u g h the use of insecticides for sorghum stem available to sorghum researchers in West A f r i c a , borer c o n t r o l may be unattractive to the small are important requisites. farmer, the number of large-scale sorghum farmers 4. A method of predicting outbreaks of sorghum w h o require and can afford insecticides is increasing, stem borers is needed. Such a m e t h o d should be especially in Nigeria. A number of insecticides have amenable to use by individual farmers in view of been identified in field screening trials and can be the c o m m u n i c a t i o n difficulties existing in West recommended f o r use. Africa. Pheromone trapping is a possibility.

2 9 5. Knowledge of the d i s t r i b u t i o n of sorghum stem A b u , J . F . 1986b. Dry-season p o p u l a t i o n s of Sesamia cala- borers is still inadequate in some parts of West mistis Hampson (Lepidoptera: Noctuidae) on sorghum at A f r i c a . T h e only comprehensive studies seem to Mokwa in the southern Guinea savanna zone of Nageria. Presented at the 16th Annual Conference of the Nigerian have been made in Nigeria ( H a r r i s 1962, A b u Society for Plant Protection, 16-20 Mar 1986, Ahmadu 1986a, b) and B u r k i n a Faso (Nwanze 1985). Bello University, S a m a r u , Z a r i a , Nigeria, 1 1 p 6. Effects of the changing c r o p p i n g systems in some parts of West A f r i c a , on the stem borer species Adesiyun, A . A . 1983. Some effects of intercropping of c o m p l e x and activity, needs to be elucidated. In sorghum, millet and maize on infestation by lepidopterous stalk-borers, particularly Busseola fusca. Insect Science Nigeria, f o r example, large farms of m o n o c r o p - a n d its A p p l i c a t i o n 4 ( 1 - 2 ) : 3 8 7 - 3 9 1 . ped s o r g h u m have been developed. A l s o , maize is fast replacing millet in some parts of the southern Adesiyun, A . A . 1986. C o n t r o l of the stem borer, Busseola and n o r t h e r n Guinea savannas. In a d d i t i o n , fusca. Insect Science and its Application 4:3-11.

wheat is being g r o w n under irrigation d u r i n g the Adesiyun, A . A . , and Ajayi, O. 1980. C o n t r o l of the d r y season in the northernmost parts of the c o u n • s o r g h u m stem borer Busseola fusca by partial burning of t r y and Scsamia is the o n l y stem borer so far the stalks. Tropical Pest Management 26(2):113-117. recorded on wheat ( A j a y i 1986). The role of Ajayi, O.1978. Control of sorghum, millet and wheat field wheat in enhancing the survival of Sesamia dur- insect pests. Pages 116-126 in Proceedings of the 2 n d ing the d r y season has not been studied. N A F P P W o r k s h o p o n S o r g h u m , M i l l e t and W h e a t , 17-19 7. T h e n u m b e r of entomologists currently w o r k i n g A p r 1978, S a m a r u , Z a r i a , Nigeria: A h m a d u Bello on s o r g h u m insects in the region is grossly inade• University. quate, as is the level of research f u n d i n g . There is Ajayi, O. 1986. T h e incidence of stem borers on irrigated an urgent need to strengthen sorghum research wheat in Nigeria. S a m a r u Miscellaneous Paper n o . 108. t h r o u g h national programs in the region. Samaru, Zaria, Nigeria: Institute for Agricultural Research.

Ajayi, O. 1987. Insecticidal control of the sorghum stem C o n c l u s i o n borer. Pages 35-38 in Cereals Research Programme. Crop- ping Scheme Report, 1987. Samaru, Zaria, Nigeria: Insti- The identification, distribution, and relative impor• tute for Agricultural Research. tance of stem borers of sorghum in West A f r i c a have Gahukar, R . T . 1981. Biological c o n t r o l of insect pests of been studied. Busseola fusca and Sesamia, especially s o r g h u m a n d pearl millet in West A f r i c a . Pages 69-91 in S. calamistis, are the major stem borers. B. fusca is Biological control of pests: its potential in West Afri c a : more i m p o r t a n t in the n o r t h e r n Guinea savanna proceedings of an International Conference, 9-13 Feb while Sesamia predominates in the wetter southern 1981, Dakar, Senegal. Dakar, Senegal: United States Guinea savanna, although there are pockets in the Agency for International Development, Regional Food latter where B. fusca predominates. Control mea• Crop Protection Project. 15 pp. sures have been developed for b o t h stem borers. Harris, K . M . 1962. L e p i d o p t e r o u s stem borers of cereals in These include the destruction of stems to k i l l the Nigeria. Bulletin of Entomological Research 53 stem borer larvae, intercropping w i t h millet, the use (1):139-I71. of stem-borer resistant varieties, and the application IAR (Institute for Agricultural Research.) 1975. E n t o m o l - of insecticides. M a n y natural enemies of the stem ogy Pages 28-38 in Cereals Improvement Programme: borers have been identified but further studies are report to the Board of G o v e rn o rs on the Institute's w o r k in needed before they can be effectively used in biologi• 1974-75. Samaru, Zaria, Nigeria: IAR. cal c o n t r o l programs. It is desirable to integrate those measures that are compatible in order to attain IAR (Institute for Agricultural Research). 1976. E n t o m o l - ogy. Pages 17-38 in Cereals I m p r o v e m e n t P r o g r a m m e : economic control of the stem borers. report to the Board of G o v e rn o rs on the Institute's w o r k in 1975-76. Samaru, Zaria, Nigeria: IAR.

IAR (Institute for Agricultural Research). 1984. S o r g h u m . R e f e r e n c e s Science and technology briefing, Lagos, December 1984. S a m a r u , Z a r i a , Nigeria: I A R . A b u , J . F . 1986a. Biology and control of the insect pests of s o r g h u m in the southern Guinea savanna zone of Nigeria. Ingram, W . R . 1958. T h e L e p i d o p t e r o u s stalk borers asso- S a m a r u , Z a r i a , Nigeria: Institute f o r A g r i c u l t u r a l ciated with Gramineae in Uganda. Bulletin of Entomolog i - Research: 23 p p . cal Research 49:367-383.

3 0 M a c F a r l a n e , J . H . 1984. E v a l u a t i o n o f i n t e r n a t i o n a l a n d local insect pest nurseries. ICRISAT/SAFGRAD/IAR J P 3 1 F i n a l report, Part I I I . S a m a r u , Z a r i a , N i g e r i a : Insti- tute f o r A g r i c u l t u r a l Research. 17pp.

Nwanze, K . F . 1985. S o r g h u m insect pests in West A f r i c a . Pages 37-43 in Proceedings of the International Sorghum Entomology Workshop, 15-21 Jul 1984, College Station, Texas, U S A . Patancheru, A . P . 502 324, I n d i a : I n t e r n a - t i o n a l C r o p s Research Institute f o r the S e m i - A r i d T r o p i c s .

3 1

Sorghum Stem Borers in Eastern Africa

K.V. Seshu Reddy1

Abstract

Twelve stem borer species have been recorded on sorghum in eastern Africa. C h i l o partellus, C. orichalcociliellus, Eldana saccharina, Busseola fusca, Sesamia calamistis, and S. cretica are the most important. The distribution, biology, ecology, and grain yield losses caused by these stem borers and their management are discussed.

Introduction dence, crop losses, biology, ecology, physiology, and the management of stem borers of sorghum in east• In eastern A f r i c a , sorghum (Sorghum bicolor [ L . ] ern A f r i c a n countries. Moench) is a traditional staple crop for millions of people. It is also g r o w n as feed for poultry and livestock in the f o r m of grain, forage, and fodder. A D i s t r i b u t i o n o f S t e m B o r e r s number of countries in the eastern A f r i c a n region are working on sorghum improvement including: The wide range of lepidopterous stem borer species Burundi, Ethiopia, Kenya, Rwanda, Somalia, Sudan, infesting sorghum in the region of eastern Africa is Tanzania, and Uganda. W o r l d production of sor• indicated in Table 1. However, the most notorius g h u m grain totals approximately 63 m i l l i o n metric species in these countries are: Chilo partellus, tonnes, produced on some 47 m i l l i o n hectares. In C. orichalcociliellus, Eldana saccharina, Busseola eastern A f r i c a , where 12.5% of the world's acreage is fusca, Sesamia calamistis and S. cretica. under s o r g h u m , grain yield is very low, w i t h an A l t h o u g h C. partellus occupies the low w a r m and average of 1090 kg ha-1, compared w i t h 3063 kg ha- 1 humid areas of sorghum production, it has been in the U S A ( F A O 1984). One of the major con• r e c o r d e d at an a l t i t u d e of 1800 m, whereas straints to production is insect pests. C. orichalcociliellus is confined to coastal areas of Lepidopterous stem borers are the most wide• Kenya and Tanzania. B. fusca occurs in mid-altitude spread g r o u p of insect pests of sorghum in eastern and highland areas. In Ethiopia, the occurrence of A f r i c a . On late-planted sorghum, infestations of B. fusca is relatively rare around 1200 m but its these insects can cause substantial grain yield losses severity often intensifies during periods of relatively on small-scale farms. This paper briefly discusses the warm temperature. It usually phases out, with C. advances made in the studies on distribution, inci- partellus and S.calamistis increasing in prominence

1. Senior Research Scientist, International Centre of Insect Physiology and Ecology (lC1PE), P.O. Box 30, Mbita, Kenya. lCRISAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, I C R I S A T Center, India. Patancheru, A.P. 502 324, India: ICRlSAT.

33 S. calamistis, and E. saccharina ranged f r o m 95- Table 1. Stem borers of sorghum in eastern Africa1 . 100%. Larval and pupal populations, measured per Countries r e p o r t i n g the 40 plants, ranged widely: C. partellus 0-14, B. fusca Stem borer presence of borer 40-174, and S. calamistis 0-34. Generally, the popu-

Chilo partellus ( S w i n h o e ) E t h i o p i a , K e n y a , S o m a l i a , lation of E. saccharina was l o w , ranging f r o m 0 - 2 ( s o r g h u m stem borer) Sudan, Tanzania, Uganda. per 40 plants. These four stem borer species were also f o u n d feeding on the same sorghum plant. Chilo orichalcociliellus Kenya, Tanzania. In Uganda, 5 6 % grain yield losses occurred when Strand (coastal stalk borer) sorghum was infested by C. partellus at 20 days after Eldana saccharina W a l k e r Burundi, Kenya, Rwanda plant emergence (DAE) (Starks 1969). In field stud- ( A f r i c a n sugarcane borer) S o m a l i a , Tanzania, ies conducted at the I C I P E ' s M b i t a Point Field Sta- Uganda. t i o n in western Kenya, grain yield losses in sorghum Ematheudes sp. nr. Uganda. caused by C. partellus reached 74.4% when plants helioderma were infested w i t h 5 larvae/plant at 10 D A E . Losses

Busseola fusca Fuller Burundi, Ethiopia, Kenya, were 87.8% when plants were infested w i t h 10 lar- (maize stalk borer) Rwanda, Sudan, Tanzania, vae/plant, at 10 DAE. As plant development ad- Uganda. vanced, initial larval infestation caused lower yield losses, as l o w as 2 - 1 3 % at 60 D A E . In research Busseo la segeta B o w d e n T a n z a n i a , Uganda. elsewhere in the region, in Tanzania, it was reported Sesamia calamistis Burundi, Ethiopia, Kenya, that B. fusca is typically f o u n d in sorghum at H a m p s o n ( A f r i c a n p i n k Rwanda, Tanzania, 40-100% infestation (Jepson 1954), and Megenasa stalk borer) Uganda. (1982) reported that in Ethiopia, movement of Sesamia cretica Ethiopia, Kenya, Somalia, B. fusca larvae into the base of the sorghum head Lederer S u d a n . resulted in undersized heads and a 15% grain loss.

Sesamia a/bivena B u r u n d i H a m p s o n Bionomics, Ecology, and Physiology Sesamia botanephaga Kenya, Sudan, Tanzania, Tarns & Bowden Uganda In eastern A f r i c a , the biology and ecology of major Sesamia penniseti Uganda stem borer species of sorghum have been studied by Tarns & B o w d e n several workers (Jepson 1954, Ingram 1958, Nye Sesamia poephaga Kenya, Tanzania, Uganda 1960, Wheatley 1961, de Pury 1968, Schmutterer Tarns & B o w d e n 1969, M a t h e z 1972, Bohlen 1973, G i r l i n g 1978, and

1. Sources: I n g r a m 1958. N y e I 9 6 0 , G e b r e k i d a n 1982. Seshu N u r 1978). R e d d y 1985a, a n d Seshu R e d d y a n d O m o l o 1985. In Kenya, field and laboratory investigations conducted on diapause associated w i t h aestivation by larvae of C. partellus and C. orichalcociliellus, showed that while sufficient moisture was available for plant growth, development was continuous and as altitude drops (Megenasa 1982). E. saccharina is the larvae had pigmented spots. On the cessation of considered to be the most i m p o r t a n t stem borer and rain or irrigation, the cuticular pigment was lost, and a head pest of sorghum in B u r u n d i ( K a b i r o 1982). In larvae became resistant to drought and ceased feed- Somalia and Sudan b o t h C. partellus and 5. cretica ing. Temperature, relative humidity, and day length are serious ( A l i o 1986, and Farrag 1986). did not affect diapause, indicating that changes in the food-plant might be responsible (Scheltes 1978). However, inquiry into larval development showed I n f e s t a t i o n a n d Losses that it was possible to rear B. fusca throughout the year on y o u n g sorghum stems w i t h o u t any interven- In western Kenya, it is rare to find healthy sorghum ing diapause, while feeding on mature stems induced plants in many farmers' fields at harvest. A m o n g the diapause (G.C. Unnithan, personal communication). damaged plants, extent and density of stem borers Preliminary electrophysiological tests on certain vary. In studies conducted in farmers' fields, infesta• tarsal and ovipositor sensilla of adults of C. partellus tions of borer complexes C. partellus, B. fusca. and £. saccharina, showed that the sensilla were

34 innervated by mechano- and contact- chemorecep- Table 2. Natural host plants of sorghum stem borers. t o r cells. Tarsal receptors were sensitive to sucrose, whereas the oviposition sensilla were not (Waladde C. par- Sesamia E. sac- 1983). Host plant tellus B.fusca spp charina

2 Cenchrus ciliaris + 1 -

H o s t R a n g e Echinochloa colonum + +

Echinochloa Several host plants of sorghum stem borers have haploclada + + been recorded and documented by various workers (Jepson 1954, I n g r a m 1958, Le Pelley 1959, and Nye Echinochloa 1960). Surveys to f i n d various natural hosts of the pyramidalis + sorghum stem borers were conducted in the environs Hyperrhenia rufa + of L a k e V i c t o r i a in western Kenya. Several species Leptuous repens + + + + of plants were f o u n d to harbor stem borers (Table 2). Of these plants, B. fusca damage was recorded as a Panicum maximum + + + percentage on several species: Hyperrhenia rufa Pennisetum (26%); Pennisetum macrourum (53%); Phragmites macrourum + + mauritianus (34%); and w i l d sorghum (49%). Cype- Pennisetum rus ariticulata was identified as an i m p o r t a n t host of purpureum + + + E. saccharina, w i t h up to 4 2 % plants damaged. Sesamia spp were f o u n d to infest C. papyrus (47%) Phragmites and Typha latifolia (35%). mauritianus + + Sorghum arundinaceum + + +

C o n t r o l M e t h o d s Sorghum verticilliflorum + + + C u l t u r a l C o n t r o l Sporobolus marginatus S o w i n g D a t e Cyperus articulata + + + It has been f o u n d that early sowing of sorghum Cyperus papyrus + + resulted in less infestation by stem borers than the late-planted crop in western Kenya. Destruction of Kyllinga sp. + + crop residues, stubble, volunteer and alternate host Typha latifolia + plants have been suggested by different workers to 3 + reduce borer infestations (Duerden 1953, Jepson Launaea c o m m a

1954, I n g r a m 1958, Nye 1960, Seshu Reddy 1985a, 1. + = R e c o r d e d host. and U n n i t h a n and Seshu Reddy 1986). 2. - = N o t r e c o r d e d . 3. O n l y eggs were seen.

Intercropping

In Tanzania, K a t o et al. (1982) observed that ovipo- build-up, and establishment of stem borer com- sition response of insect pests such as shoot fly and plexes of C. partellus, B. fusca, E. saccharina and stem borers (C. partellus, B. fusca, and S. calamistis) S. calamistis have also been related to different was higher in sorghum monocrops than in mixed sorghum/cowpea/maize combinations (Omolo and crops of sorghum and simsim. Also, fewer dead- Seshu Reddy 1985). hearts were recorded in intercropped sorghum than in pure stands of maize. In Kenya, A m o a k o - A t t a et al. (1983) established Fertilization that intercropping noncereal/cereal combinations delays C. partellus colonization and establishment In Uganda, f o l l o w i n g nitrogen and phosphorus fer- processes. Early and late infestation, colonization. tilizer applications, greater populations of C. panel-

35 lus were f o u n d in grain sorghum plots (Starks et al. wide range of mechanisms were involved in C. par- 1971). In S u d a n , S i d d i q (1972) f o u n d that applica- tellus resistance in sorghum including nonpreference t i o n of nitrogenous fertilizer to sorghum increased for oviposition, reduced feeding of the first-instars the infestation of C. partellus and S. cretica. on y o u n g leaves, reduced tunneling activity of the first-instars on y o u n g leaves, reduced tunneling activity of older larval instars, and tolerance of P l a n t R e s i s t a n c e plants b o t h to leaf damage and stem tunneling. Morphological, physical and other plant character- An i m p o r t a n t prerequisite for identifying sources istics, which are easily detectable and are of practical and mechanisms of plant resistance to sorghum stem plant breeding value, need to be further studied to borers is the capacity for mass p r o d u c t i o n of the determine their c o n t r i b u t i o n to resistance. borers themselves. A m e t h o d of steady p r o d u c t i o n Studies on genetics of s o r g h u m resistance to of C. partelIus has been established at the I C I P E , C. partellus in Kenya demonstrate that resistance is K e n y a and an efficient, simple and easy method of polygenically inherited, and partially d o m i n a n t to collection of first-instar larvae from the incubation susceptibility (Pathak and Olela 1983). In Uganda, chamber has been developed (Ochieng et al. 1985). Starks and Doggett (1970) made significant advan- E v a l u a t i o n of s o r g h u m f o r resistance to stem bor- ces in b o t h breeding methodologies and incorpora- ers has been standardized using t w o categories of t i o n of resistance to C. partellus. A l t h o u g h several parameters: colonizing levels of insects on different sources of s o r g h u m resistance to stem borers are cultivars; and degree of damage suffered by them. available in eastern A f r i c a , little effort has been T h e parameters f o r the colonizing levels are: o v i p o - made to incorporate the resistance into high-yielding sition (percentage of eggs laid); and number of lar- cultivars. vae/pupae per plant, or per 10 plants. Damage parameters include: the p r i m a r y damage expressions, e.g., foliar lesions (visual rating on 1-5 or 1-9 B i o l o g i c a l C o n t r o l scales); stem tunneling (percentage of stem length); deadheart (percentage of plants showing the symp- In eastern A f r i c a , the role of natural enemies (parasi- t o m ) ; and secondary damage expressions, e.g., stalk toids, predators, and pathogens) as a cause of popu- breakage a n d / or head breakage ( K . N . Saxena, per- lation fluctuations in stem borers of sorghum has sonal communication). been investigated by several workers (Jepson 1954, In the Ethiopian sorghum improvement program Ingram 1958, Schmutterer 1969, Mohyuddin and nearly 6000 indigenous Ethiopian sorghum germ- Greathead 1970, Mathez 1972, Megenasa 1982, and plasm entries have been evaluated under hot spot Seshu Reddy 1983, 1985a). natural infestation for their reactions to B. fusca. In Kenya, three egg parasitoids ( t w o scelionids Barely 1% of the entries were rated tolerant. H o w - and a trichogrammatid) caused up to 9 2 % mortality ever, they were rated susceptible under more rigor- in Chilo spp and 9 7 % in 5. calamistis. Parasitism of ous tests in subsequent seasons (Gebrekidan 1981). larvae and pupae was usually below 10% although Seshu Reddy (1983 and 1985b), based on screening eight parasitoids were f o u n d together w i t h a further w o r k in Kenya, reported several promising sources six possible parasitoids ( M a t h e z 1972). M o h y u d d i n of resistance to sorghum stem borer complex. These (1972) suggested that Dentichasmias busseolae. a include: IS nos. 1044, 1151,3962,4213,4405,5613, solitary pupal endoparasitoid (and one of the abun- 10364, 10370, 10711, 12447, 18326, 18427, 18479, dant and widely distributed parasitoids), could play 18517, 18676, S-178, Tx 2780, and A & B Tx 2756. a significant role in reduction of C. partellus popula- Based on the overall resistance and susceptibility tions in eastern Africa. Parasitism ranged f r o m index ( O R S l , the ratio of each parameter value for a 6-58%. In western Kenya, parasitism of C. partellus cultivar to that for the control), resistant sorghum by D. busseolae has been recorded at 11 weeks after cultivars include Tx 38, IS nos. 4660, 3962, 10370, plant emergence reaching a peak of 6 0 % t w o weeks 10711, and 4 8 8 1 . IS 1044 and S-178 were found to be after. Incidence dropped to 15% at 14 weeks and highly resistant relative to the control IS 18520. The again rose to a m a x i m u m of 7 0 % at 16 weeks ( J . W . lower the O R S l value f o r a cultivar (<1.0) the Bahana personal communication). greater its overall resistance ( K . N . Saxena, personal Investigations in Uganda considered the possible communication). biological control of E. saccharina, by the parasitic D a b r o w s k i and Kidiavai (1983) reported that a bethylid, Parasierola spp. A laboratory colony of

36 the parasitoid was established on the larvae of P h e r o m o n e a n d L i g h t T r a p s E. saccharina in stems of s o r g h u m . Up to 22 adult bethylids were produced f r o m one host larva and Pheromone traps containing either synthetic or vir- the sex ratio was 7 females to 1 male. Larvae of gin females could be used in m o n i t o r i n g stem borer C. partellus, B. fusca, and S. calamistis were not populations in the field. In western Kenya, mean accepted as hosts but those of C. partellus were c a t c h e s / t r a p / n i g h t in pheromone traps w i t h virgin occasionally paralyzed and used as f o o d in the females were highest for Maliarpha separatella (a absence of E. saccharina ( G i r l i n g 1979). Releases of rice stem borer) followed by C. partellus and. B. fusca exotic parasitoids Apanteles flavipes, Bracon chi- ( H o and Seshu Reddy 1983). Further studies showed nensis, Isotima javensis, Trichogramma australi - that B. fusca virgin females were more than t w o cum, and Sturmiopsis inferens against B. fusca, times as efficient as synthetic pheromones in attract- S. calamistis, C. partellus, and E. saccharina have ing males, and mated females did not attract males. not been successful in eastern A f r i c a ( I n g r a m 1983). However, in C. partellus, traps containing virgin In western Kenya, stem borers are parasitized by females attracted a much higher percentage of males the parasitoids Trichogramma spp., Apanteles se- (89%) than synthetic pheromone-baited (4%) or samiae, Pediobius furvus, and D. busseolae. Pro- blank (7%) traps. Even after mating and oviposition, d u c t i o n , development, sex ratio, and longevity of C. partellus females continued to attract males, these parasitoids have been studied in the region. although not as well as the virgin moths (G.C. U n n i - A l s o , techniques for mass culture of i m p o r t a n t para- than, personal communication). sitoids of sorghum stem borers have been initiated Various factors which influence trap catches, and ( G . W . O l o o , personal communication). could be used to standardize trapping techniques, In Kenya, Mathez (1972) considered unidentified were also considered. It was observed that traps with bacteria, viruses, and fungi the most important limit• C. partellus virgin females set 40 m apart attracted ing fact oh to larvae of C. partellus, C. orichalcoci- more males than those set 20 m apart. V i r g i n females liellus, and S. calamistis in the field. Spore suspen- reared on artificial diet attracted males as efficiently sion application of a protozoan Nosema spp. to as those reared on natural diet (sorghum). The sorghum plants infested w i t h first-instar C. partellus number of males trapped increased as the number of larvae, effectively controlled the borer. Also, appli- virgin females increased per trap, up to a m a x i m u m cation of a nematode, Panagrolaimus sp is being of 4 females/trap. The attractability of the virgin investigated as a t o o l in integrated management of females declined w i t h age (G.C. U n n i t h a n , personal sorghum stem borers ( M . O . O d i n d o and W . A . communication). Otieno, personal communication). Preliminary studies conducted in western Kenya I n f o r m a t i o n on the role of predators in stem borer showed M. separatellato have the highest attraction control is scanty. However, in Kenya, earwigs (Dia- to light traps, followed in descending order by perasticuserythrocephala), black ants (Camponotus C. partellus, E. saccharina, S. calamistis, and B. rufoglaucus), lady bird beetles (Cheilomenes spp.), fusca ( H o and Seshu Reddy 1983). and spiders have been recorded as predators of the major stem borers of sorghum.

Integrated Pest Management (IPM) C h e m i c a l C o n t r o l In Kenya, the m a i n goal of the I C I P E C r o p Pests In eastern A f r i c a , several workers have used insecti- Research Program is to develop ecologically accep- cides to c o n t r o l B. fusca under experimental condi- table management strategies to control sorghum tions (Duerden 1953, Coaker 1956, Swaine 1957, stem borers. These strategies must also be economi- I n g r a m 1958, Walker 1960, Schmutterer 1969, Ma- cally and sociologically feasible for resource-poor, thez 1972, Bohlen 1973, and Assefa 1981). Chemical small-scale farmers in A f r i c a and other developing c o n t r o l of sorghum stem borers is expensive and has countries. Components that are being developed f o r not proven to be economically feasible on subsist- integrated management of stem borers belong to the ence farms. Other drawbacks to chemical control following categories: plant resistance; intercropping include the dangers of environmental p o l l u t i o n , the of certain specific combinations of host and nonhost potential for pest resistance, and post-control pest crops; other cultural practices such as sowing date, resurgence. crop residues, disposal, etc; biological control, use of

3 7 parasitoids and pathogens, and behavioral manipu- R e f e r e n c e s lation.

Alio, A . N . 1986. Status of c r o p a n d livestock pests in Somalia. Pages 38-40 in Proceedings of the I n t e r n a t i o n a l C o n c l u s i o n Working Group on the Implementation of the African Regional Pest Management Research and Development Stem borers are a major constraint in sorghum Network (PESTNET) for Integrated Control of Crop and p r o d u c t i o n in eastern A f r i c a . There is a long history Livestock Pests, 22-26 Jun 1986, Nairobi, Kenya.

of interaction between various species of stem borers Amoako-Atta, B., Omolo, E.O., and Kidega, E.K. 1983. and s o r g h u m , especially w i t h C. partellus, C. ori- Influence of maize, cowpea and sorghum intercropping chalcoclliellus, B. fusca, S. calamistis, S. cretica, and systems on stem/-pod-borer infestations. Insect Science E. saccharina. Development of borer-resistant sor- and its Application 4(l-2):47-57. ghum cultivars, use of efficient natural enemies, and Assefa, G . A . 1981. Some p r e l i m i n a r y studies on maize cultural c o n t r o l practices could contribute substan- stalk borer Busseola fusca ( F u l l e r ) in E t h i o p i a . M.Sc. the- tially to the management of these stem borers under sis, A d d i s A b a b a University, N a z r e t h , A d d i s A b a b a , subsistence agriculture. Although sources of sor- E t h i o p i a . g h u m resistance to stem borers are available in the Bohlen, E. 1973. Crop pests in Tanzania and their control. region, little progress has been made in incorporat- H a m b u r g , Federal Republic o f G e r m a n y : Verlay Paul ing resistant genes into agronomically elite mate- Parey. 142 pp. rials. Host-plant resistance w i l l have to play a Coaker, T . H . 1956. An experiment on maize stalk borer greater role t h a n it has in the past. C u l t u r a l practices control on maize. East African Agricultural Journal such as intercropping sorghum w i t h nonhosts, field 21:220-221. sanitation, and adjustment of sowing dates could play a significant role in reducing yield losses caused Dabrowski, Z.T., and Kidiavai, E.L. 1983. Resistance of some sorghum lines to the spotted stalk-borer Chilopartel- by stem borers. lus under western Kenya conditions. Insect Science and its As I n g r a m (1983) suggested, although some effec- Application 4(1-2): 119-126. tive parasitoids have already been identified, critical ecological studies are required to p i n p o i n t more pre- de Pury, J.M.S. 1968. Crop pests of East Africa. Nairobi, cisely where the addition of further parasitoid spe- Kenya: Oxford University Press. 227 pp. cies are most likely to be effective. Such studies Duerden, J.C. 1953. Stem borers of cereal crops at should assess the role of stem borers and parasitoids Kongwa, Tanganyika 1950 52. East African Agricultural in w i l d host plants in relation to: dry seasons; crop J o u r n a l 19:105-119. infestations; relative effectiveness of egg, larval, and F A O . 1984. 1983 FAO Production Yearbook, vol.37. p u p a l parasitoids; the effect of predators and patho- Rome, Italy: FAO. 320 pp. gens; and possible changes in agronomic practice to Farrag, Y.H.A. 1986. Food crop pests in Sudan. Page 42 in enhance the effectiveness of natural enemies. Such Proceedings of the International Working Group on the studies could contribute to a more effective p r o g r a m Implementation of the African Regional Pest Managem e n t of introductions, mass rearing, and large-scale re- Research and Development Network (PESTNET) for leases of the natural enemies. Very little is k n o w n Integrated Control of Crop and Livestock Pests, 22-26 J u n about stem borer predation other than the occa- 1986, Nairobi, Kenya. sional references to black ants, earwigs, coccinellid Gebrekidan, B. 1981. Ethiopian Sorghum Improvement beetles and spiders attacking eggs and early larval Project Progress Report no. 9. Nazreth, Ethiopia: Addis instars. S i m i l a r l y , the role of pathogens such as p r o - Ababa University, and Institute of Agricultural Research. tozoan Nosema, fungi, bacteria, and nematodes Gebrekidan, B. (ed.) 1982. S o r g h u m i m p r o v e m e n t in east- should be explored in traditional small-scale and ern Africa: proceedings of the Regional Workshop, 17-21 peasant farms. Hence, there is m u c h need f o r the Oct 1982, Nazreth and Debre Zeit, Ethiopia. Nazreth , development of environmentally safe, economically Ethiopia: Ethiopian Sorghum Improvement Project. 196 and sociologically acceptable management strate- pp. gies f o r the stem borers of s o r g h u m , n o t only in Girling, D . J . 1978. The distribution and biology of Eldana eastern A f r i c a but throughout the tropical w o r l d . saccharina Walker (Lepidoptera: Pyralidae) and its relationship to other stem borers in Uganda. Bulletin of En t o - mological Research 68:471-488.

38 Girling, D . J . 1979. Parasierola sp. (Hym: Bethylidae), a N u r , A . F . 1978. B io lo g y and c o n t r o l of the spotted stalk parasite of Eldana saccharina Wlk. (Lep: Pyralidae). Ento- borer, Chilo partellus (Swinhoe) in Somalia. M.Sc. thesis, mologists' Monthly Magazine 113:211-212. University of Wyoming, Laramie, Nyoming, USA.

H o , D . T . , and Seshu Reddy, K.V. 1983. Monitoring of Nye, I . W . B . 1960. The insect pests of graminaceous crops lepidopterous stem-borer population by pheromone and in East Africa. Colonial Research study no.31. London, light traps. Insect Science and its A p p l i c a t i o n 4( 1 -2): 19-23. U K : H e r Majesty's Stationery Office. 48 pp.

Ingram, W . R . 1958. The lepidopterous stalk borers asso- Ochieng, R.S., Onyango, F.O., and Bungu, M.D.0.1985. ciated with Gramineae in Uganda. Bulletin of Entomolog- I m p r o v e m e n t of techniques f o r mass culture of Chilo p a r - ical Research 49:367-383. tellus (Swinhoe). Insect Science and its Application 6(3): 425-428. Ingram, W . R . 1983. Biological control of graminaceous stem-borers and legume pod-borers. Insect Science and its Omolo, E.O., and Seshu Reddy, K.V. 1985. Effects of Application 4(1-2):205-209. different sorghum-based cropping systems on insect pests in Kenya. Pages 395-401 in Proceedings of the Interna- Jepson, W . F . 1954. A critical review of the world literature tional Sorghum Entomology Workshop, 15-21 Jul 1984, on the lepidopterous stalk-borers of tropical graminaceous College Station, Texas, USA. Patancheru, A.P. 502 324, crops. London, UK: Commonwealth Institute of Entomol- India: International Crops Research Institute for the S e m i - ogy. 127 pp. Arid Tropics. Kabiro, Z. 1982. R e p o r t on s o r g h u m i m p r o v e m e n t in Pathak, R.S., and Olela, J.C. 1983. Genetics of host plant B u r u n d i . Pages 79-84 in Sorghum improvement in eastern resistance in food crops with special reference to sor g h u m A f r i c a : proceedings of the Regional W o r k s h o p , 17-21 Oct stem-borers. Insect Science and its Application 4(1-2 ): 1982, Nazreth and Debre Zeit, E t h i o p i a , ( G e b r e k i d a n , ed.) 127-134. Nazreth, E t h i o p i a : E t h i o p i a n S o r g h u m I m p r o v e m e n t P r o - ject. A d d i s A b a b a University, E t h i o p i a n S o r g h u m Scheltes, P. 1978. Ecological and physiological aspects of I m p r o v e m e n t Project. 196 p p . aestivation-diapause in the larvae of two pyralid stalk- borers of maize in Kenya. Wageningen, Netherlands: L a n d - Kato, D . , Karel, A . K . , a n d Ndunguru, B.J. 1982. Effect of bourwhogeschool 110 pp. insecticide spray on insect pests and yield of s o r g h u m and simsim in pure stand and i n t e rc ro p p in g. Pages 117-118 in Schmutterer, H. 1969. Pests of crops in Northeast a n d I n t e r c r o p p i n g : proceedings of the Second S y m p o s i u m on Central Africa with particular reference to Sudan. Stut- Intercropping in Semi-Arid Areas, 4-7 Aug 1980, Moro- tgart, Federal Republic of Germany: Gustar Fischer Ver- goro, Tanzania (Keswani, C.L., and Ndunguru, B.J., eds.) lag. 296 pp. Ottawa, Canada: International Development Research Seshu Reddy, K.V. 1983. Studies on stem borer c o m p l e x of Centre. (Abstract). sorghum in Kenya. Insect Science and its Application Le Pelley, R . H . 1959. Agricultural insects of East Africa. 4(1-2):3-10. N a i r o b i , Kenya: East A f r i c a n H i g h C o m m i s s i o n . 307 pp. Seshu Reddy, K.V. 1985a. Integrated approach to the con- Mathez, F.C. 1972. Chilo partellus S w i n h . , C. orichalcoci- t r o l of s o r g h u m stem borers. Pages 205-215 in Proceedings liella Strand (Lep: Crambidae) and Sesamia calamistis of the International Sorghum Entomology Workshop, H m p s . (Lep: Noctuidae) on maize in the Coast Province, 15-21 Jul 1984, College Station, Texas, USA. Patancheru, Kenya. Mitteilungen der Schweizerischen Entomologi- A.P. 502 324, India: International Crops Research Insti- schen Gesellschaft 45:267-289. tute for the Semi-Arid Tropics.

Megenasa, T. 1982. Insect pests of sorghum in Ethiopia. Seshu Reddy, K.V. 1985b. Relative susceptibility and res- Pages 54-64 in S o r g h u m i m p r o v e m e n t in eastern A f r i c a : istance of some s o r g h u m lines to stem borers in Western proceedings of the Regional Workshop, 17-21 Oct 1982, Kenya. Insect Science and its Application 6(3):401-404. Nazreth and Debre Zeit, E t h i o p i a ( G e b r e k i d a n , B., ed.) Seshu Reddy, K.V., and O m o l o , E.O. 1985. S o r g h u m Nazreth, E t h i o p i a : E t h i o p i a n S o r g h u m I m p r o v e m e n t insect pests situation in eastern Africa. Pages 31-36 in Project. Proceedings of the International Sorghum Entomology M o h y u d d i n , A . I . 1972. Distribution, biology and ecology Workshop, 15-21 Jul 1984, College Station, Texas, USA. of Dentichasmiasbusseolae Heinr. (Hym: Ichneumonidae) Patancheru, A.P. 502 324, India: International Crops a pupal parasite of graminaceous stem borers ( L e p . , P y r a l i - Research Institute for the Semi-Arid Tropics. dae). Bulletin of Entomological Research 62:161-168. Siddiq, S.A. 1972. Graminaceous stem borers in the n o r t h - M o h y u d d i n , A . I . , and Greathead, D . J . 1970. An annotated ern province of Sudan. I. Ecological studies. Zeitschrift list of parasites of graminaceous stem borers in East A f r i c a , fuer Angewandte Entomologie 71:376-381. with a discussion of their potential in biological cont r o l . Starks, K.J. 1969. Some cereal c r o p insects in East A f r i c a . Entomophaga 15:241-274. Kampala, Uganda: East African Agriculture and Forestry Research Organization, Sercre Research Station.

39 Starks, K.J.,and Doggett, H. 1970. Resistance to a spotted stem borer in s o r g h u m a n d maize. J o u r n a l of E c o n o m i c Entomology 63:1790-1795.

Starks, K.J., Schumaker, G.,and Eberhart, S.A. 1971. S o i l fertility and damage by C h i l o zonellus ( S w i n h o e ) on grain s o r g h u m . J o u r n a l o f E c o n o m i c E n t o m o l o g y 64:740-743.

Swaine, G. 1957. T h e maize and s o r g h u m stalk borer Bus- seolafusca ( F u l l e r ) , in peasant agriculture in T a n g a n y i k a Territory. Bulletin of Entomological Research 48:711-722.

Unnithan, G . C . , a n d Seshu Reddy, K.V. 1986. Infestation and carryover of s o r g h u m stem borer and the potential role of destruction of c r o p residues as a c u l t u r a l c o n t r o l practice. Page 32 in Proceedings of the International Confer- ence on Tropical Entomology, 31 Aug-5 Sep 1986, N a i r o b i , Kenya.

Waladde, S . M . , 1983. Chemoreceptors of adult stem borers: tarsal a n d o v i p o s i t o r sensilla on Chilo partellus and Eldana saccharina. Insect Science and its A p p l i c a t i o n 4(l-2):159-165.

Walker, P.T. 1960. Insecticide studies on the maize stalk borer Busseola fusca ( F u l l e r ) in East A f r i c a . Bulletin of Entomological Research 51:521-531.

Wheat ley, P.E. 1961. T h e insect pests of agriculture in the Coast Province of Kenya. 6. M a i z e and s o r g h u m East African Agricultural and Forestry Journal 27:105-107.

4 0 Sorghum Stem Borers in Southern Africa

S.Z. Sithole'

Abstract

The four stem borers attacking sorghum in southern Africa are the spotted stem borer (Chilo partellus Swin), which is the most important, maize stalk borer (Busseola fusca Fuller), pink stem borer (Sesamia calamistis Hmps), and sugarcane stem borer (Eldana saccharina Wlk). Control strategies include the use of cultural and chemical methods with little or no use of bioagents and resistant genotypes. Moth migration has been identified as an important bionomic factor. Thus, synthetic pheromones have an important role to play in integrated stem borer management. Current research activities are geared towards the use of resistant sorghum genotypes, defining the extent of sorghum stem borer infestations and their subsequent translation into yield losses.

Introduction 1980, van Rensburg and M a l a n 1982, Sam et al. 1985, Sithole 1986, van Rensburg et al. 1987, Sko- In southern A f r i c a , grain sorghums are g r o w n p r i • roszwski and V a n H a m b u r g 1987). The maize stalk- marily for h u m a n consumption. Surpluses are used borer (B. fusca), spotted stem borer (C. partellus), for feeding different classes of livestock (Sibanda pink stem borer (S. calamistis), and (E. saccharina) 1985). Grain yields f r o m fields of resource poor constitute the most economically important group farmers are low, ranging f r o m 600 to 900 kg ha-1. of insect pests of sorghum. Under heavy infestation, One of the major constraints responsible for low these borers are capable of rendering a whole crop of yields is insect pests (Seshu Reddy 1982). sorghum useless. The relative importance of these Stem borers have proven to be the most economi• stem borers in the subregion varies f r o m one agro- cally i m p o r t a n t insect pests of sorghum and maize in ecological region to another. Infestations range southern A f r i c a (Blair 1971, van Rensburg et al. f r o m 3 0 - 7 0 % in subsistence farmers' fields but aver• 1978, van H a m b u r g 1976,1979,1980, van Rensburg age less than 30% on commercial farms. To date, no

1. Plant Protection Research Institute, Department of Research and Specialist Services, P.O. Box 8100, Causeway, Harare, Zimbabwe. lCRISAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987,lCRISAT Center. India. Patancheru, A.P. 502 324, India: lCRISAT.

4 1 sorghum yield-loss studies have been conducted in peduncle breakage, and stunted g r o w t h of the whole southern A f r i c a , but current research in Z i m b a b w e plant. seeks to q u a n t i f y the impact of stem borers on Damage symptoms ascribed to S. calamistis attack sorghum yield. Current research activities in sor- may be distinguished f r o m those due to B. fusca and g h u m e n t o m o l o g y in the subregion are directed C. partellus in several ways. In S. calamistis, the t o w a r d gaining i n f o r m a t i o n on stem borer migra- central leaves wither and t u r n b r o w n , and increased t i o n , and developing c o n t r o l measures t h r o u g h tillering is initiated. No feeding marks are f o u n d on timely use of insecticides, cultural practices, bio- the leaves but an external borer-hole may be found c o n t r o l agents, sex pheromones, and resistant sor- near soil level at the base of the stem. Walters et al. g h u m varieties. (1980) and V a n Rensburg (1981) described loss of maize yield due to B. fusca as 'tremendous' while Revington (1986) estimated losses due to C. partel- D a m a g e a n d Y i e l d Losses lus to be more than 50% in the highlands. Recent w o r k by the author (unpublished) indicated that loss Busseola fusca, C. partellus, and E. saccharina pro- in sorghum yield can range f r o m 5 0 - 6 0 % due to duce more or less similar damage symptoms in C. partellus. sorghum and maize plants. N e w l y hatched larvae migrate f r o m oviposition sites to feed on rolled developing leaves. A f t e r a few days, the leaves u n r o l l D i s t r i b u t i o n a n d B i o l o g y to reveal characteristic patterns of small holes, resembling hail damage, w h i c h are inflicted by the S p o t t e d S t e m b o r e r , C. partellus feeding larvae. As the larvae mature w i t h i n the plant funnels, they attack different parts, b o r i n g into the Chilo partellus invaded the A f r i c a n content f r o m stem below the funnel leaves. Once established I n d i a ( M o h y u d d i n and Greathead 1970). It was first inside the stem, larvae are protected and are m u c h reported in South A f r i c a in 1958 (van H a m b u r g less vulnerable to insecticides and natural enemies. 1979). It is the most i m p o r t a n t sorghum stem borer The larvae feed and tunnel inside the stems and prior in the subregion. A l t h o u g h it may cause severe losses to p u p a t i o n , cut exit holes, t h r o u g h which the moths in maize, C. partellus prefers sorghum as its food emerge. This exit is often seen covered by a t h i n plant. Unpublished w o r k by Berger has indicated 'membrane' of stem tissue. Stem-tunneling weakens that C. partellus has 3 or more generations in south- the stem, interferes w i t h the translocation of metab- ern M o z a m b i q u e , especially where maize is g r o w n olites and nutrients w i t h i n the plant, resulting in throughout the year (Fig. 1). First generation moths m a l f o r m a t i o n of grain. Other symptoms associated emerge w i t h the onset of the rainy season f r o m Sep- w i t h stem borer attack are deadhearts, stem or tember to November, and lay eggs on leaves of the

J u l A u g Sep Oct N o v Dec Jan Feb M a r A p r M a y J u n

Figure 1. Seasonal changes in the number of moths of Chilo partellus during the year.

4 2 early plantings of maize and sorghum. Newly hatched Busseola fusca is the dominant stem borer species larvae attach themselves to leaves by spinning-off of sorghum at high elevations in southern A f r i c a t h i n silk threads, and are launched into the air by the (Table 1). However, this author has observed high wind to infest neighboring plants (Berger, personal infestations of the pest on sorghum even at low communication, Revington 1986). Revington has elevations in Zimbabwe, where very low infestations described this as an instinctive dispersal mechanism, w o u l d be expected. Clearly, this shows the capability serving to reduce competition between larvae that of the pest to adapt itself to l o w - l y i n g and warmer hatch f r o m the same egg batch and thereby increase areas. Busseola fusca has t w o generations per year their survival chances. The same indications have but in some seasons a t h i r d generation may appear, been given by van Rensburg and van H a m b u r g depending on prevalent environmental conditions (1975) and V a n H a m b u r g (1979, 1980) in South and the availability of suitable host plants. At the Africa, Berger (personal communication) in M o z a m - onset of the dry season, second generation larvae bique and C h a p m a n et al. (1983) in India. Investiga- enter into diapause in tunnels at the bases of drying tions on this dispersal ability, in southern A f r i c a , has sorghum stems. These larvae pupate later, in about shown a decline w i t h increase in age of the larvae. mid-October, with the arrival of summer rains. M o t h s emerge three weeks later. The moths lay eggs on the bases of leaf sheaths. The eggs take about a Maize Stalkborer, B. fusca week to hatch and the newly hatched larvae migrate This is the second most i m p o r t a n t sorghum borer in to feed on tender leaves in the funnel before boring the subregion, and among the insect pests of maize into the stem. Unpublished results of investigations B. fusca is generally regarded as the most economi- into larval m i g r a t i o n in Z i m b a b w e have indicated cally i m p o r t a n t pest (Annecke and M o r a n 1982). that migration is density-dependent. Peak migratory Busseola fusca is indigenous to southern Africa and activity was observed among second generation lar- prefers maize as a host plant but causes serious losses vae. The development of larvae and pupae lasts to grain sorghum (Skoroszewski and van H a m b u r g about 2 months. The emergence of second-genera- 1987). t i o n moths reaches a peak d u r i n g the period f r o m Figure 2 summarizes the life-cycle of B. fusca. van mid-February to March (Fig. 2). Larvae which fail Rensburg et al. (1987) reported on the ecology of to attain full development prior to the onset of the B. fusca and recommend that the m o n i t o r i n g of dry season enter into diapause and pupate with the B. fusca infestations be conducted between 3- and arrival of the summer rains. In September, the 6-weeks after the emergence of the maize crop in weather warms up and w i t h available sorghum or order to determine the correct t i m i n g of chemical maize under irrigation, the diapausing larvae pupate control measures. and third generation moths emerge later.

Eggs

Larvae

Pupae

Adults

Jul A u g Sep Oct N o v Dec Jan Feb M a r A p r M a y J u n

Figure 2. Seasonal changes in the occurrence of different stages of Busseola fusca during the year (modified after Blair 1971).

4 3 Table 1. Distribution of lepidopterous stem borer of sorghum in southern Africa.

Elevation ( m ) and percentage S t e m borer relative abundance1

E c o n o m i c C o m m o n importance H i g h M e d i u m L o w name Scientific name C o u n t r y rank2 > 9 0 0 700-900 < 7 0 0

Spotted Chilo partellus Botswana 1 stem borer (pyralidae) M a l a w i 1 5 40 70 M o z a m b i q u e 1 South Africa 1 Swaziland 2 Z i m b a b w e 1

Maize Busseola fusca Botswana 2 stalkborer (Noctuidae) Lesotho 1 90 18 10 M a l a w i 2 M o z a m b i q u e 2 S o u t h A f r i c a 2 Swaziland 1 Z i m b a b w e

Pink Sesamia calamistis M a l a w i 3 stem borer (Noctuidae) M o z a m b i q u e 3 5 40 10 S o u t h A f r i c a 3 Z i m b a b w e 3

Sugarcane Eldana saccharina M o z a m b i q u e 4 0 2 10 stem borer (Pyralidae) S o u t h A f r i c a 4 Swaziland 4 Z i m b a b w e 4

1 . I n f o r m a t i o n a r i s i n g f r o m a n i n v e s t i g a t i o n c o n d u c t e d b y theauthorduring the 1985/86 cropping season. Percentage relative a b u n d a n c e i s inclusive o f a l l c o u n t r i e s i n the r e g i o n w h i c h have d i s t r i b u t i o n o f the c o r r e s p o n d i n g borers n o t e d o n this table. 2. R a n k scale of 1 - 5 . w h e r e 1 = highest a n d 5 = lowest e c o n o m i c i m p o r t a n c e .

Pink Stem Borer Sesamia calamistis site. Development is completed in the stem after about 6-10 weeks. The pupal period lasts for 2 weeks The pink stem borer, 5. calamistis, attacks sorghum after which the moths emerge. T w o generations of i n M a l a w i , M o z a m b i q u e , S o u t h A f r i c a , and Z i m - the pest have been observed in a year by the author. babwe. It is most prevalent at m e d i u m elevations (Table 1). Sesamia calamistis is unique in that its feeding habits are different f r o m those of B. fusca Sugarcane Stem Borer, Eldana saccharins and C. partellus. No feeding marks are f o u n d on the leaves of the host plant, but external borer-holes The pyralid, E. saccharina Walker, is an important may be noticed near ground-level in the base of the pest of sugarcane in southern Africa and hence the stems. Central leaves wither and t u r n b r o w n and c o m m o n name sugarcane stem borer ( A t k i n s o n suckers are produced. In southern A f r i c a , very Iittle 1982). It occurs in M o z a m b i q u e , South A f r i c a , Swa- research has been done on this pest, w h i c h is of little ziland, and Zimbabwe (Table 1). It has become a consequence to sorghum yield. Female moths have serious pest of sugarcane in recent times in the coast- been observed laying eggs between the base of the al sugarcane-growing areas of Natal, in South leaf sheath and the main stem. Larvae hatch w i t h i n a Africa, and the southeastern part of Zimbabwe. week and bore into the stem close to the oviposition A l t h o u g h it is k n o w n to attack maize and sorghum

4 4 in the subregion, E. saccharina appears to be of very been recommended to spray d u r i n g the period little importance in maize and sorghum production. between 15 and 30 D A E . Newly hatched larvae feed on leaves and bore into the stem when they are fully g r o w n . The larvae spin off silken threads by which they hang d o w n f r o m Cultural Control plants and are b l o w n by w i nd to neighboring plants. The larval period lasts for about 3-8 weeks after Theoretically, there are several cultural measures which p u p a t i o n , lasting 1-2 weeks, commences that could adversely affect stem borer population in inside the stem. Female moths lay up to 200 eggs. a sorghum field. However, the practicality and the success of some of these measures as permanent control tactics are questionable. Such measures as early and simultaneous planting, disposal of sor- C o n t r o l o f S o r g h u m S t e m B o r e r s ghum residues by burning, or burial by deep plowing d u r i n g the off-season, removal and destruction of C h e m i c a l C o n t r o l volunteer and alternative host plants, and crop rotation are helpful in reducing stem borer infestations Evaluation of insecticides for the control of sorghum and their impact on yield. Intercropping has long stem borers has received considerable attention been practiced by subsistence farmers, but little f r o m entomologists in southern A f r i c a , in recent research attention has been given to this aspect in years. Chemical control measures against grain southern Africa. sorghum stem borers are based on the use of contact and systemic insecticides, as spray or dust treatments to the foliage. However, significant control Host-plant Resistance results have been achieved in the subregion w i t h carbofuran 10% granules at 1 or 2 kg a.i. ha- 1 ( W a l - The use of resistant -varieties is, by far, the most ters and D r i n k w a t e r 1975, van Rensburg 1980, and promising control measure in reducing yield losses van Rensburg and Malan 1982). Other insecticides caused by stem borers. A l t h o u g h this type of control in use include carbaryl, endosulfan, trichlorfon, and is recognized to be economical and environmentally synthetic pyrethroids. These insecticides have been safe, the use of resistant varieties is very limited as no screened in different sorghum localities and the ones research work has been done on varietal resistance in identified as being the most effective have been southern Africa. The existence of the Southern released to farmers through the extension service. African Development Coordination Conference The profit margin for sorghum is currently very low (SADCC)-ICRISAT Program to improve sorghum with the result that resource-poor farmers often and millet production in the subregion, has spear- cannot afford to spray against sorghum stem borers. headed the current screening of sorghum germplasm It is therefore not surprising that the use of insecti- for resistance to stemborers. cides by these farmers is not widely practiced. C o n - sequently, the use of insecticides for the control of sorghum stem borers is more or less restricted to Biological Control large-scale and government-comrolled farms. Apart f r o m the evaluation of insecticides for their effec- A number of parasites and predators of sorghum tiveness against stem borers, some w o r k is now being stem borers have been recorded but very few studies done to find out the appropriate methodologies and on their effectiveness, as well as host/parasite rela- t i m i n g of insecticide application, with a view to tionships, have been conducted. A l t h o u g h the role reducing the frequency and thus the cost of appli- of predators is not easy to assess, ants, spiders, mites, cation. and reduviids are often encountered close to cadav- In a drive to protect maize f r o m C partellusd a m - ers of stem borer larvae. Entomologists in southern age, the current recommendation is to start spraying Africa have shown interest in the use of biocontrol 10-14 days after crop emergence ( D A E ) , or f r o m the agents in controlling stem borers of maize and two-leaf to four-leaf stage with the initial spray ap- sorghum. Biocontrol agents of interest in the subre- plied within 21 DAE(Revington 1986). Similar stud- gion include egg parasitoids such as Trichogramma ies by Sithole (unpublished) of the C. partellus on sp (Trichgrammatidae), larval parasitoids including sorghum gave more or less similar results, and it has Apanteles sesamiae Cam. (Braconidae), and pupal

45 parasitoids, e.g. Dentichasmias busseolae Heinrich Berger, A. 1982. Controle biologico da broca ponteada (Ichneumonidae), and Pediobius furvus (Gah.) (Eul- Chilo partellus (Swinhoe) no m i l n o c o m a bacteria Bacillus ophidae). Skoroszewski and van H a m b u r g (1987) thuringiensis. Estudo do populacao da praga e evaliacao dos prejuizos por ela causados. Relaterio anual 1980/81 . investigated the possibility of controlling B. fusca P.O. Box 7044, 5.75007 U P P S A Z A , Sweden.(In Pt.). and C. partellus using an introduced larval parasi- t o i d , Apanteks flavipes (Cameron). In Mozam- Blair, B.W. 1969. A p r e l i m i n a r y report on the sex phero- bique, w o r k on C. partellus (Goncalves 1970) re- m o n e of the maize stalk borer (Busseola fusca Fuller) ( L e p i - vealed the importance of Trichoramma sp in para• doptera: Noctuidae). Rhodesian Journal of Agricultura l Research 7:55-59. sitizing eggs, and A. sesamiae in parasitizing larvae. Berger (1981) recorded D. busseolae H e i n r i c h , Blair, B.W. 1971. Recent research on the maize stalkborer P. furvus Gah. and Lepidoscelio sp. (Scelionidae) as (Busseola fusca Fuller): influence on control methods. parasites of pupae reaching levels of 10 14% parasit• Rhodesian Agricultural Journal 68(6): 111 112. ism. However, it should be noted that the level of Chapman, R.F., Woodhead, S., and Bernays, E.A. 1983. parasitism by these parasites is generally low under S u r v i v a l and dispersal of y o u n g larvae of Chilo partellus natural conditions. (Swinhoe) in t w o cultivars of Sorghum hicolor. Bulletin of In southern A f r i c a , Blair (1969), and Hall et al. Entomological Research 73:65-75. (1981), discussed the effectiveness of a female sex- Goncalves, L. 1970. A broca do M i l h o Chilo partellus pheromone obtained f r o m the 8th and 9th a b d o m i • Swinhoe (Lep. Crambidae) em Mozambique. (In Pt.) nal segments of B. fusca in controlling the pest. The Agronomia Mocambicana 4(4): 239 246. effective pheromone has been characterized and syn• H a l l , D . R . , Beevor, P.S., Cork, A . , Lester, R., Nesbitt, thetic pheromones tested under field conditions. B.F., Nyirenda, G.K.C., Nota Phiri, D.D.,Blair, B.W.,and C o n t r o l of the pest is achieved by incorporating the Tannock, J. 1981. The female sex pheromone of the maize pheromone as a bait in traps or in general applica• stalk-borer, Busseola fusca (Fuller) (Lepidoptera: Noctui- tion to confuse the male moths, which are then either dae): identification and initial field trials. Zimbab w e J o u r - killed or sterilized by chemical means. Since females nal of Agricultural Research 19:111 122. mating with sterile males produce no progeny, the Mohyuddin, A.I., and Greathead, D.J. 1970. An annotated pest population can successfully be reduced to a list of the parasites of graminaceous stem borers in East subeconomic damage level. Africa, with a discussion of their potential in biological control. Entomophaga 15:241-274.

Page, L.J.S., M g u n i , C M . , and Sithole, S.Z. 1985. Pests Conclusions and diseases of crops in c o m m u n a l areas of Z i m b a b w e : technical report. Overseas Development Administratio n , Scientists interested in increasing sorghum produc• U K : O D A . tion in southern Africa need to put more research Revington, J. 1986. This borer spreads rapidly t h r o u g h efforts on the following: distribution, biology, and crops of maize and s o r g h u m on The H i g n v e l d . But it can be behavior of stem borer species; use of sex phero• controlled. Farmer's Weekly, 24 Oct 1986. mones for m o n i t o r i n g adult populations; use of resistant sorghum cultivars; and f o r m u l a t i n g and Sibanda, S. 1985. The use of s o r g h u m and millets f o r feeding livestock. Pages 228 247 in Proceedings of the implementing integrated and location-specific stern Second Regional Workshop on Sorghum and Millets for borer management program. In addition, yield loss Southern Africa, 23-27 Sep 1985, Gaborone, Botswana, investigations need to be conducted at research sta• Bulawayo, Zimbabwe: Southern African Development tions and on farmers' fields to generate i n f o r m a t i o n Coordination Conference/ International Crops Research for devising stem borer control strategies. Institute for the Semi-Arid Tropics.

Sithole, S.Z. 1986. The effect of date of p l a n t i n g on R e f e r e n c e s snootily and stemborer infestations on s o r g h u m . Pages 174-183 in Proceedings of the T h i r d Regional W o r k s h o p A n n e c k e , D . P . , a n d M o r a n , V . C . 1982. Insects and mites of o n S o r g h u m and Millets for S o u t h e r n A f r i c a , 6-10 Oct cultivated plants in S o u t h A f r i c a . D u r b a n , S o u t h A f r i c a : 1986, Lusaka, Z a m b i a , B u l a w a y o , Z i m b a b w e : Southern Butterworths. 382 pp. African Development Coordination Conference/Interna-

Atkinson, P.R. 1982. Structure of the putative pheromone tional Crops Research Institute for the Semi-Arid Tropics. glands of Eldana saccharina Walker (Lepidoptera: Pyrali- dae). J o u r n a l of E n t o m o l o g i c a l Society of S o u t h e r n A f r i c a 45(0:93-104.

4 6 Skoroszewski, R . W . , and van H a m b u r g , H. 1987. T h e Walters, M.C., and Drinkwater, T.W., van Rensburg, release of Apanteles flavipes (Cameron) (Hymenoptera: J.B.J., and Boshoff, L. 1980. The maize stalkborer: Preto- Braconidae) against stalk borers of maize and g r a i n ria, South Africa: Division of Agricultural Informati o n . sorghum in South Africa. Journal of the Entomological Society of Southern A f r i c a . 50(1): 249 255.

van H a m b u r g , H. 1976. Die bionomie en ekonomiese bclangrikheid van die graansorghumstamruspe, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae). (In Af.) D.Sc.thesis. University of Pretoria, Pretoria, South A f r i c a .

van H a m b u r g , H. 1979. The grain sorghum stalkborer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae): seasonal changes in adult populations in grain s o r g h u m in the Transvaal. J o u r n a l of the E n t o m o l o g i c a l Society of S o u t h - ern A f r i c a . 42(1): 1-9.

van H a m b u r g , H. 1980. The grain s o r g h u m stalkborer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae): survival and location of larvae at different infestation levels in plants of different ages. J o u r n a l of the E n t o m o l o g i c a l Society of Southern A f r i c a 43(1): 71-76.

van Rensburg, R.J. and van H a m b u r g , H. 1975. G r a i n sorghum pests: an integrated c o n t r o l a p p r o a c h . Proceed- ings of the Congress of the E n t o m o l o g i c a l Society of Southern A f r i c a 1:151 162.

van Rensburg, J.B.J., Walters, M . C . , and Stemmet, G.P. 1978. A preliminary study on the application of c a r b o f u r a n granules to the soil for the c o n t r o l of grain sorghum pests. Phytophylactica 10:28 30.

van Rensburg, J.B.J. 1980. The use of granular formulations of insecticides for the c o n t r o l of insect pests in grain sorghum. Proceedings of the Congress of the E n to mol og i c - al Society of Southern A f r i c a 3:52 53. (Abstract.).

van Rensburg, J.B.J. 1980. Selective oviposition by the maize stalkborer, Busseola f u s c a (Fuller). Proceedings of the Congress of the Entomological Society of Southern A f r i c a 3:23 24.

van Rensburg, J.B.J. 1981. Die plaagstatus van Busseola fusva (Fuller):'n Studie Plaag-tot-Gewasverhousings. (In A f . ) P h . D . thesis, University of stellenbosch, Cape P r o - vince, S o u t h A f r i c a .

van Rensburg, G . D . J . , and M a I a n , E . M . 1982. C o n t r o l of sorghum pests and p h y t o t o x i c effect of c a r b o f u r a n on five hybrids of grain sorghum. Phytophylactica 14:159 163.

van Rensburg, J.B.J., Walters, M.C., and Gilliomee, J.H . 1987. Ecology of the maize stalkborer, Busseola fusca (Fuller) (Lepidoptera: Noctuidae). Bulletin of Entomolo g i - cal Research 77:255 269.

Walters, M . C . , and Drinkwater, T . W . 1975. Preliminary studies on the application of systemic insecticides to the soil for the c o n t r o l of the maize stalk borer, Busseola fusca (Fuller) (Lep.: Noctuidae). Phytophylactica 7:121-124.

Sorghum Stem Borers in Central and South America

R. Reyes1

Abstract

This paper presents a literature review of the two major sorghum stem borers in Central and South America: Diatraea lineolata Walker and Diatraea saccharalis Fab. Their importance, distribution, seasonal abundance, host plants, and life cycles are discussed. Control measures that are currently practiced (cultural, biological, and chemical) are also presented.

Introduction consumption and in Brazil it is commercially grown for alcohol production (Bertels 1982a, Paul and de S o r g h u m Sorghum bicolor (L.) M o e n c h is one of the Walt 1985, and Pereira et al. 1987). most widely g r o w n cereal crops in Central and M i h m (1984) pointed out that the complex D i a - South America (Table 1). In 1985, approximately traea spp. is the most i m p o r t a n t group of stem bor- 3.2 m i l l i o n ha were harvested w i t h a grain yield of ers that attack maize, sorghum, and sugarcane Sac- about 8.5 m i l l i o n tonnes w i t h 73% of production charum officinarum. Harris (1985) noted that dif- coming from Argentina. Grain yield ranged from ferent species of pyralid sorghum stem borers have 0.714 4.75 t ha-1 ( F A O 1986, p. 121). In some coun• been recorded: D. lineolata W a l k . , D. saccharalis tries, low-resource farmers g r o w native sorghums, Fab., D. crambidoides Grote, and Elasmopalpus intercropped mainly with maize, Zea mays L., pro• lignosellus Zeller. Since these borers are considered ducing low sorghum grain yields (Paul and de Walt occasional or minor pests, research on them in rela- 1985, and C A T 1 E 2 1986). In contrast, when i m • tion to sorghum has been limited. proved sorghum varieties are g r o w n commercially in Most of the w o r k on stem borers has been con- mechanized monoculture, with higher inputs, yields- ducted on sugarcane and maize, influencing this increase substantially (Juarez and Valdez 1978, and review to include i n f o r m a t i o n on these crops. The C E N T A 1980). species infesting maize and sorghum in Central and S o r g h u m is used mainly for animal feed, in con• South America are c o m m o n to most countries of the centrates and as fodder. It is also g r o w n for h u m a n region (Seshu Reddy 1985). Mendonca (1986) and

Coordinator, Sorghum Program, Centro Nacional de Tecnologia Agricola (CENTA), La Libertad, Apartado Postal 885, San Salvador, 1. El Salvador. 2. Centro Agronomico Tropical de Investigacion y Ensenanza.

ICR1SAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, l C R l S A T Center, India. Patancheru, A.P. 502 324, India: ICRlSAT.

4 9 Table 1. Sorghum grain production in Central America, Sugarcane Borer Antilles, and South America during 19851. (Diatraea saccharalis Fabricius)

Area Produc- Neotropical Cornstalk Borer harvested t i o n Yield (D. lineolata Walker) C o u n t r y ('000) ha) ('000 t) (t ha-1 )

Central America 330 523 1.63 Distribution

Guatemala 66 89 1.35 El Salvador 116 139 1.20 Diatraea spp. occur only on the American continent. H o n d u r a s 48 50 1.04 S C B is the most widely distributed species of the Nicaragua 74 194 2.61 genus. It is found f r o m southern N o r t h America, Costa Rica 26 51 1.95 Central A m e r i c a , and the Antilles south to A r g e n • tina in South America (Fig. 1) N C B , the second most Antilles 140 130 1.36 widely distributed borer, ranges from Central Amer• C u b a 1F2 1F 1.10 ica and the Antilles to northern South America, D o m i n i c a n including C o l o m b i a , Venezuela, Guianas, and Ecua• Republic 17 52 3.02 dor. N C B was first recorded f r o m Venezuela in 1856 3 H a i t i 120 75 0.62 (Bleszynsky 1969, Peairs and Saunders 1980, K i n g Neth A n t i l l e 2 E 2 E 0.71 and Saunders 1984, and Harris 1985). In addition, N C B has been reported in N o r t h America, western South America 2 725 7 796 2.60 and northern M e x i c o , and south Texas, U.S.A. C o l o m b i a 207 537 2.60 (Box 1949, Hodges 1983, and Y o u m 1984). Venezuela 3053 590 1.93 Ecuador 33 123 3.57 Peru 5 23 4.75 Host Plants Brazil 163 258 1.58 Bolivia 7 14 2.01 N C B is more limited in its host range than is SCB; Paraguay 7F I 0 E 1.43 U ruguay 63 152 2.40 the latter is considered polyphagous. Myers, cited by A r g e n t i n a I 965 6 200 3.15 Peairs and Saunders (1980) affirms that originally, S C B was in the riversides and that its primitive hosts 1. FAO 1985. were likely aquatic or semiaquatic grasses such as 2. F = FAO estimate. 3. U n o f f i c i a l f i g u r e . Paspalum, Echinochloa, Leptochloa, and Hyme- nachne. N C B and SCB attack crops of economic importance such as sugarcane, maize, sorghurn (sweet sorghum, and b r o o m corn), wheat, and rice. Table 2 lists additional host plants (Jepson 1954. Peairs and Saunders (1980) have reviewed stem bor- Requena and Angeles 1966, and Peairs and Saund- ers on sugarcane and maize, while Teetes et al. ers 1980). According to Quintana and Walker (1970) (1980), Harris (1985), and Seshu Reddy (1985), pro- in Puerto Rico, the preferred hosts, for ovipositing vide a review of these insects on sorghum. and development of SCB young larvae were maize, A c c o r d i n g to several studies ( O b a n d o 1975, Se- sugarcane, s o r g h u m , Euchlaena mexicana, and queira et al. 1976, Sequeira et al. 1986, and Reyes et Coixlachryma-jobi. al. 1987) the neotropical corn stalk borer ( N C B ) D. lineolata W a l k is the most i m p o r t a n t sorghum stem borer in Central America. In South America, L i f e C y c l e however, the most important stem borer is the sugarcane borer (SCB), D. saccharalis Fab. (Geraud The life cycles of the N C B and S C B are very similar. 1970, Ruiz and K o r i t k o w s k i 1975, Bertels 1982a, In Central America w o r k has been carried out on and Viana 1985). Given the many similarities be- maize by Sequeira et al. (1976) and K i n g and Saund- tween the t w o species, the present review will not ers (1984) on the different development stages. Egg deal independently on each borer but will relate and masses of 1-13 eggs are laid in juxtaposed files at share topical i n f o r m a t i o n relating to these borers in b o t h sides of the top leaves, appearing yellow as a c o m m o n . scale ( O b a n d o 1975). Larvae hatch about 30 days, or

5 0 5 1 Table 2. Some host plants of Diatraea saccharalis Fab. reported in the Antilles, Central and South America.1

H o s t plant C o m m o n name L o c a t i o n

Axonopus compressus Bermuda grass West Indies Coix lachryma-jobi Job's tears West Indies, Puerto R i c o Curcuma longa T u r m e r i c Venezuela Cymbopogon schoenanthus Lemon grass C u b a Cyperus ligularis N u t grass Venezuela Echinochola colonum - C u b a E. polystacha - British G u i a n a , Venezuela Eleusine indica Goose grass C u b a Euchlaena mexicana - Puerto Rico Sorghum sudanense Sudan grass C u b a S. halepense Johnson grass C u b a Hymenachne amplexicaulis - Orinoco delta H. donacifolia - Haiti, British Guiana Leptochloa virgata - C u b a L. scabra - Puerto Rico Oriza latifolia W i l d rice Venezuela O. sativa Rice A r g e n t i n a Panicum elephantipes - South America Paspalidium geminatum - H a i t i Panicum grande - Venezuela Paspaium fasciculatum T a l l grass Venezuela P. virgatum - Puerto Rico P. repens - British Guiana, Orinoco Pennisetum purpureum Napier grass Puerto Rico Saccharum oficinarum Sugarcane South America Tricholaena rosea Natal grass C u b a Valota insularis S o u r grass C u b a lea mays M a i z e , c o r n South America

1. Sources: J e p s o n 1954, R e q u e n a a n d A n g e l e s 1966. a n d Peairs a n d S a u n d e r s 1980.

100-150 days in diapause. The larva undergoes days. Pupae are b r o w n w i t h t w o pointed protuber- seven instars and measures 20-25 mm in length when ances in the head, like horns, w h i c h are longer in mature. Y o u n g larvae feed on tender leaves for 2-3 S C B than in N C B . A d u l t s live for 4 days, and days after hatching, before entering the stem. Usu- develop a m a x i m u m wing expanse of 20-42 m m . ally they enter between the leaf sheath in the superior S C B has a diagonal file of b r o w n dots more or less part of the plant, then bore into the stem, removing defined in the forewings, but identification must be frass f r o m the tunnel, and m a k i n g one or more holes c o n f i r m e d by examining the genitalia (Bleszynski to the exterior. At the end of the season, in response 1969). The life cycle f r o m egg to adult can last f r o m to the quality deterioration of the f o o d , some mature 45-165 days, depending u p o n the diapause period. larvae undergo a prolonged period of resting (facul- Quezada (1979) suggested 3-4 generations could be tative diapause). This lasts f o r the remainder of the completed per year. d r y season, as the larvae settle in the b o t t o m part of In Sao Paulo, Brazil, Bertels (1982a) indicated the d r y stem w i t h o u t p u p a t i n g , u n t i l rains start that each S C B egg mass can have f r o m 30-40 eggs, again. and a female can lay up to 600 eggs d u r i n g its life. In E1 Salvador, Quezada (1979) f o u n d 2 1 % of The life cycle of S C B largely depends on the time of larvae diapausing, of w h i c h 5% died due to desicca- year, as well as temperature and h u m i d i t y . In winter, t i o n or attack by entomopathogenes. Likewise, larval instars can last up to 3 months due to l o w Reyes et al. (1987) recorded 2 2 % of diapausing lar- temperatures and high h u m i d i t y . I n R i o Grande d o vae on native sorghum. Larvae pupate in the stem S u l , Brazil, and probably also in Uruguay, there are close to an exit hole and p u p a l period lasts f o r 7-12 4 - 5 annual generations. In the tropical regions of

5 2 Venezuela, this number increases significantly. High farmers have concerning the pest and its influence on h u m i d i t y is unfavorable to spring generations, which grain p r o d u c t i o n (Obando and V a n Huis 1977). greatly reduces summer attack. Observations made by Harris (1985) suggest that attack at harvest is highest on high-yielding plants, possibly as a result of preferential oviposition by Damage female moths on superior plants. In S o u t h A m e r i c a , Busoli et al. (1979) in Sao Damage inflicted to sorghum crops depends on the Paulo, Brazil, found that SCB in sorghum reached development of the plants. I m p r o v e d sorghum var- peak infestation in M a y , whereas in R i o de Janeiro, ieties are susceptible to borer attack f r o m 25-30 days Pereira et al. (1987) a f f i r m that sorghum planted in after emergence ( D A E ) . The larva tunnels into the October and November is most affected. In Peru, stem k i l l i n g the growing point, producing dead- S i m o n and A r e l l a n o (1959) reported that stem borer hearts, a s y m p t o m that may also result f r o m attack damage is more intense in the summer than in the by E. lignosellus and termites (Termitidae: Isoptera). spring. This c o n d i t i o n can produce loss of plant stand or delayed m a t u r i t y because of tiller p r o d u c t i o n . H o w - ever, if y o u n g plants are seriously attacked, the Host-plant Resistance whole plant may d r y up. If the top internode is bored after floral differentation and before head emer- In Brazil, the sweet sorghums BR 501, BR 504, and gence, the top leaves may d r y u p , and the emerged BR 505 have good levels of S C B resistance ( A m a r a l head could be completely empty. If the damage et al. 1980, and Pereira et al. 1987). In addition, occurs d u r i n g or after head emergence, it can result sorghum AF 28, whic h is also resistant to sorghum in partially filled heads. Generally, this damage midge Contarinia sorghicola C o q . , showed levels of occurs after the sorghum plants have flowered and is 13% infestation, and sorghum EA 177, 26% infesta- f o u n d in very localized areas w i t h i n a plantation. tion (Lara et al. 1979). Busoli et al. (1979) in Brazil, and Reyes et al. (1983) in E1 Salvador, reported up to 4 8 % of infested plants in improved sorghum varieties. L o d g i n g and Cultural Control attack by microorganisms, such as Colletotrichum sp. and Fusarium sp., are favored by stem borer Poor farmers f r o m Central America usually feed damage (Geraud 1970, Reyes et al. 1983, and Harris their cattle maize and sorghum stubble d u r i n g the 1985). Losses due to stem borers are generally d i f f i - dry season, whic h helps to reduce the diapausing cult to assess precisely. The number of pest species larvae populations (Quezada 1979, and C A T I E involved, the different types of damage, the plant 1986). Several other cultural control measures have developmental stages attacked, and often the pres- been suggested: destruction of stubble 1-2 months ence of other insects and microorganisms have made before the onset of the rainy season; gathering and it difficult to determine their effect on yield (Seshu burning of stubble, or incorporating it by plowing or Reddy 1985). disking; early sowing; early-maturing varieties; crop rotation (alternating Gramineae w i t h Legumino- sae); appropriate fertilization; and plant density to Seasonal Abundance favor plant vigor (Sequeira et al. 1976, Cortez et al. 1984, and K i n g and Saunders 1984). In Central A m e r i c a , sorghum planted in August is attacked more than sorghum planted in M a y because Diatraea populations increase f r o m October to Biological Control December (Sequeira et al. 1976, Lacayo 1977, and Cortez et al. 1984). In maize/ sorghum c r o p p i n g sys- The number of SCB and NCB natural enemies is tems, sorghum is damaged more due to high insect large and complex. M a n y have been recorded in populations in October and November. M a j o r infes- S C B in sugarcane, maize, and sorghum. Tables 3 tations in maize and sorghum are more likely to and 4 list some b i o c o n t r o l agents reviewed by several occur f r o m f l o w e r i n g to grain filling, w i t h 19% aver- authors. Jepson (1954) has also reviewed biological age infestation (Sequeira et al. 1986, and Reyes et al. i n f o r m a t i o n on natural enemies of stem borers in 1987). This might explain the lack of awareness that considerable detail.

53 Table 3. Distribution of egg and larva parasitoids of Diatraea saccharalis ( F a b . ) and D. lineolata ( W a l k . ) reported in Central America ( C ) , Antilles ( A ) , and South America ( S ) .

Parasitoids F a m i l y : O r d e r Distribution Reference

Egg

Trkhogramma parasitoids Minutum Riley Trichogrammatidae : Hym. C A , S Teetes et a l . 1980 T. austratkum G i r . Trichogrammatidae : Hym. A , S Teetes et a l . 1980 T. fascia turn Perk. Trichogrammatidae : Hym. S Sarmiento 1981 T. brasiliensis Trichogrammatidae : Hym. S Sarmiento 1981 Trkhogramma sp. Trichogrammatidae : Hym. C King and Saunders 1984 Teienomus alecto C r a m . Scelionidae : H y m . C, S Teetes et a l . 1980

Larva parasitoids

Lixophaga diatraea T n z . Tachinidae : D i p . A Teetes et a l . 1980 Metagonistylum minensi tns. Tachinidae : D i p . A , S Teetes et a l . 1980 Theresia (Paratheresia) ciaripalpis H u l p . Tachinidae : D i p . C, A , S Teetes et a l . 1980 Jayneleskia jaynesi A l d r . Tachinidae : D i p . S Teetes et a l . 1980 Leskiopalpus diadema W d . Tachinidae : D i p . A , S Teetes et a l . 1980 L. famelicus W i e d . Tachinidae : D i p . A Teetes et a l . 1980 Parthemoleskia parkeri Tns. Tachinidae : Dip. S Teetes et a l . 1980 Stomatodenia flauvpennis W i e d . Tachinidae : Dip. A Teetes et a l . 1980 Zenillia pa/pal is A l d r . Tachinidae : D i p . S Teetes et a l . 1980 Achaetoneura archippivora W i l l . Tachinidae : D i p . C Lacayo 1977 Archytas sp. Tachinidae : Dip. C Lacayo 1977 Eucelatoria sp. Tachinidae : D i p . C Quezada 1979 Ohysarcodexia peltata A l d r . Sarcophagidae : D i p t . S Teetes et a l . 1980 Sarcophaga lambens W i e d . Sarcophagidae : Dipt. A , S Teetes et a l . 1980 S. pedata Aldr. Sarcophagidae : Dipt. A Teetes et a l . 1980 S. rapam Walk. Sarcophagidae : Dipt. A Teetes et a l . 1980 S. sternodontis Tns. Sarcophagidae : Dipt. C K i n g and Saunders 1984 S. surrubea W u l p . Sarcophagidae : Dipt. A Teetes et a l . 1980 Apanteles xanthopus A s h m . Braconidae : H y m . S Teetes et a l . 1980 A. diatraea Mues. Braconidae : H u m . C, A K i n g and Saunders 1984 Ipobracon tucumanus Breth. Braconidae : H y m . S Teetes et a l . 1980 /. grenadensis A s h m . Braconidae : Hym. A , S Teetes et a l . 1980 /. amabilis Breth. Braconidae : H y m . S Teetes et a l . 1980 /. aquaticus Myers Braconidae : H y m . S Teetes et a l . 1980 /. puberulus Szep. Braconidae : H y m . S Teetes et a l . 1980 /. saccaharalis T u r n e r Braconidae : H y m . S Teetes et a l . 1980 /. dolens C a m . Braconidae : H y m . S Teetes et a l . 1980 /. puberuloides Myers Braconidae : Hym. S Teetes et a l . 1980 Microbracon femoratus A s h m . Braconidae : H y m . S Teetes et a l . 1980 M. chinensis Szep. Braconidae : Hym. A Teetes et a l . 1980 M. femoratus Ashm. Braconidae : H y m . A Teetes et a l . 1980 Agathis stigmaterus Cress. Braconidae : H y m . A , S Sarmiento 1981 A. (Bassus) crossi Breth. Braconidae : H y m . S Teetes et a l . 1980 A. (Bassus) parifasciatus Cam. Braconidae : H y m . S Teetes et a l . 1980 A. (Bassus) sacchari Myers Braconidae : H y m . S Teetes et a l . 1980 Iphiaulax sp. Braconidae : H y m . C Cortez et a l . 1980 / . r i m a c W o l c o t Braconidae : H y m . S Bartlett et a l . 1978 /. abancay Braconidae : H y m . S Bartlett et al. 1978 Eupelmus cushmani Cramani Cramf. Eupelmidae : Hym. S Teetes et a l . 1980 E.peruvianas C r a m f . Eupelmidae : H y m . S Teetes et a l . 1980 Spilochalcis dux W a l k Chalcididae : H y m . C, S K i n g and Saunders 1984

Continued...

5 4 Table 3. Continued.

Parasitoids Family: Order Distribution Reference

Spilocryptus diatraea M y e r s Ichneumonidae: Hym. S Teetes et a l . 1980 Eulimneria alkae E & S. Ichneumonidae : H y m . A Teetes et a l . 1980 Erethmtylus flavofuscus B r u l l . Ichneumonidae : H y m . S Teetes et a l . 1980 Perisierola bogotensis kieff Bethylidae: Hym. S Teetes et a l . 1980 Spalangia muscidarum R i c h . Pteromalidae : Hym. S Teetes et a l . 1980

Table 4. Distribution of predators of eggs and first-instar larvae, entomopathogens and hyperparasites of D. saccharalis F a b . and D. lineolata W a l k , in Central America ( C ) , Antilles ( A ) , and South America (S).

Predators Family: Order Distribution Reference

Cicloneda sangunea L. Coccinellidae : Col. C, Mendonca 1986 Coleomegilla maculata D e g . Coccinellidae : Col. C, S. Mendonca 1986 Doru lineare Esch. Forficulidae : D e r n . A , S. Mendonca 1986 Anisolabis annulipes L u c a L a b i d u r i d a e : D e r m . A. Teetes et a l . 1980 Prolabia unidentata Palis Labildae: Derm. A. Teetes et a l . 1980 Ectatona quadridens F. F o r m i c i d a e : H y m . S Teetes et a l . 1980 Monomorium fioricola Jerd F o r m i c i d a e : H y m . A. Teetes et a l . 1980 M. Carbonarium e b e n i m u n . F o r m i c i d a e : H y m . A. Teetes et a l . 1980 Forel Solenopsis corticalis F o r . F o r m i c i d a e : H y m . A Teetes et a l . 1980 Leptotrachelus testaceus puncticollis Bates Carabidae : C o l . C Teetes et a l . 1980 Chrysopa spp. Chrysopidae : Neur. C Mendonca 1986 Chrysoperla externa Hagen Chrysopidae: Neur. S Mendonca 1986 Phlugis teres D e g . Tettigonidae : O r t h . S Mendonca 1986 Leucage sp Tetragnathidae : A r a n e i d a . S Mendonca 1986 Tetragnatha sp. Tetragnathidae : A r a n e i d a . S Mendonca 1986 Epinga c.f. O r n a t a P e c k m a n Saltidae : A r a n e i d a . S Mendonca 1986

Entomopathogens

Metarhizium anisopliae (Metsch.) S o r o k i n M o n i l i a c e a : M o n i l i a l e s A , S M e n d o n c a 1986 Cordyceps barberi G i a r d Clavicipitaceae : Hypocreales c , S S h o t m a n 1978, M e n d o n c a 1986 Beauveria bassiana (Bals.) V u i l l M o n i l i a c e a : M o n i l i a l e s A , S Mendonca 1986 Entomophtora sp. E n t o m o p h t h o r a c e a e : E n t o m o p h . C Lacayo 1977 Aspergillus flavus L i n k Moniliacea : Moniliales C Lacayo 1977 Fusarium sp. Tuberculariacea : Moniliales C Lacayo 1977 Spicaria riley Moniliacea : Moniliales C Cortez et al. 1984 G r a n u l o u s V i r u s D s G V - S Mendonca 1986

Hyperparasites H o s t : Theresia claripalpis W u l p .

Trichopria cubensis Fouts Diapriidae : Proctotrupoidea. S Meza a n d K o r i t k r o w s k i 1967 Aulatopria tucwnana B r e t h . Diapriidae : Proctotrupoidea. S Meza a n d K o r i t k r o w s k i 1967 Thysanus dipterophagus G i r . Thysanidae: Chalcidoidea. S Meza a n d K o r i t k r o w s k i 1967 Melittobia sp. Eulophidae: Chalcidoidea. S M e z a a n d K o r i t k r o w s k i 1967 Conostigma sp. Ceraphronidae : Proctotrupoidea. C, S M e z a a n d K o r i t k r o w s k i 1967

55 A p p a r e n t l y , the tachinids, C u b a n fly Lixophaga C o n c l u s i o n diatraea Towns., Theresia claripalpis Wulp., and the A m a z o n i a n fly Metagonistylum minensi T o w n s , The importance of stem borers as yield-limiting fac- have been most effective in reducing Diatraea p o p u - tors in sorghum p r o d u c t i o n has been difficult to lations. Some L a t i n A m e r i c a n countries have im- assess. A l t h o u g h it is generally accepted that the ported these parasitoids and developed rearing August-sown crop suffers more damage t h a n the methodologies for inundative releases, extending M a y - s o w n c r o p , there have been no in-depth studies their d i s t r i b u t i o n range ( B o x 1952; A y q u i p a 1978; to evaluate the economic importance of borer infes- Bartlett et al. 1978, pp 179-181; S h o t m a n 1978; and tations on sorghum yield. This c o n d i t i o n may be Badilla and Solis 1984). Likewise, the braconid attributed to the fact that stem borers on sorghum, Cotesia (Apanteks) flavipes C a m . , a native f r o m which also occur on maize and sugarcane, are consid- Southeast Asia, and other parasitoids are c o m m o n l y ered occasional or m i n o r pests and research on them being used as biocontrols of S C B in sugarcane in in relation to sorghum is l i m i t e d . The way sorghum L a t i n A m e r i c a ( M e n d o n c a 1986). is generally used in Central and S o u t h America In E1 Salvador, Reyes et al. (1987) f o u n d that (animal feed and alcohol production), in contrast to techinids, braconids, and nematodes were parasi- use in A f r i c a and Asia where it is a major f o o d source toids o f N C B o n s o r g h u m . M o s t o f them have not in the diet of the p o p u l a t i o n , may also account f o r been identified, but according to Sequeira (personal this lack of information. Moreover, it appears that c o m m u n i c a t i o n ) , a m o n g the braconids Alabagrus there are a number of sorghum genotypes w i t h good sp. Iphiaulax kimballi, and Allorhogas sp. have been levels of borer resistance and this, combined w i t h the identified. Ectatoma sp is t h o u g h t to be an effective large complex of natural enemies, may explain w h y predator of NCB young larvae. The level of native farmers have not recognized stem borers as pests of parasitism in C e n t ra l A m e r i c a ranges f r o m 2 - 1 9 % economic importance. and the techinids, as well as A p a n t e l e s diatraea Mues., are the most i m p o r t a n t (Lacayo 1977, Que- zada 1979, Sequeira et al. 1986, Serrano et al. 1986, R e f e r e n c e s and Reyes et al. 1987). In E1 Salvador and H o n d u - ras, C. flavipes C a m . , bred on S C B , has been i n t r o - A m a r a l , R . A . A . , Cordeiro, D . S . , Petrini, J . A . , Porto, duced and released to control N C B in maize/sor- M . P . , Brancao, N . E . , and Dos Santos F . B . G . 1980. A ghum cropping systems. Establishment of the cultura do sorgo sacarino na regiao sudeste do Rio G r a n d e parasitoid has not been documented (Reyes et al. d o S u l . ( I n Pt.) E M B R A P A / U E P A E Pelotas C i r c u l a r 1987, and Sequeira, personal communication). Tecnica no. 12. Pelotas, Rio Grande de Sul, Brazil: U n i - dade de Execucao de Pesquisa de Ambito Estadual de Pelotas.

Chemical Control Ayquipa, A.G.E. 1978. Crianza masiva de Diatraea saccharalis Fabr. en dieta artificial para propagaci6n de su Chemical c o n t r o l is often ineffective, w i t h its t i m i n g parasito Paratheresia claripalpis W u l p . ( I n Pt.) Revista Peruana de Entomologia 21(1):55-56. restricted to the period of egg hatching and the first 3 instars, before the larvae enter the stem. This period Badilla, F . F . Y . , a n d Soils, M . I . 1984. Programadecontrol o n l y lasts about 10 days. Where the pest is i m p o r t a n t biologico del taladrador de la cana de azucar Diatraea spp. and chemical c o n t r o l is economical, it is necessary to (In Pt.) DIECA. Boletin no. 13 San Jose, Costa Rica: carefully m o n i t o r the crop to assess egg and young Direction de Investigaci6n y Extensi6n de la Cana de A z u c a r . larvae infestations. W h e n 2 5 % of the plants are infested, insecticides in dust or granular formula- Bartlett, B.R., Clausen, C.P., D e B a c h , P., Goeden, R . D . , tions can be applied into the w h o r l . Reyes et al. Legner, E . F . , M c M u r t r y , J . A . , O a t m a n , E.R., Bay, E.C., (1983) f o u n d that general applications of granular and Rosen, D. 1978. I n t r o d u c e d parasites and predators of insecticides i n t o the sorghum w h o r l to c o n t r o l Fall Arthropod pests and weeds: a world review. USDA Agri- culture Handbook no.480. Washington D.C., USA: Uni- A r m y w o r m S p o d o p t e r a frugiperda Smith, will also ted States Department of Agriculture. c o n t r o l stem borers. Bleszynsky, S. 1969. T h e t a x o n o m y of the C r a m b i n a e m o t h of sugar cane. Pages 11-41 in Pests of sugar cane (Williams, J.R. ed.). Amsterdam, Netherlands:Elsevier.

5 6 Bertels, M . A . 1982a. Insetos-pragas do sorgo a seu com- Jepson, W . F . 1954. A critical review of the world literature bate. ( I n Pt.) E M B R A P A / U E P A E Pelotas C i r c u l a r Tec- on the lepidopterous stalk-borers of tropical graminaceous nica n o . 14, Pelotas, R i o G r a n d e de S u l , B r a z i l : U n i d a d e de crops. L o n d o n , U . K : C o m m o n w e a l t h Institute o f E n t o - Execucao de Pesquisa de A m b i t o Estadual de Pelotas. 43 m o l o g y . 127 pp. p p . Juarez, V . , M . A . , and Valdez, C . W . 1978. Determinaci6n B o x , H . E . 1949. Notes o n the genus D i a t r a e a G u i l d . ( L e p i - de los costos de produccion de los sorgos para producci 6 n doptera, Pyral.) (Parts IV and V). Revista de Entomolog i a de g r a n o y forraje en variedades mejoradas y criollas. ( I n 20(l-3):541-555. Es.) Pages 52.1-52.8 in M e m o r i a , X X I V Reunion A n u a l del Programa Cooperation Centroamericano para el B o x , H . E . 1952. Campana contra los barrenos de la cana de Mejoramiento de Cultivos Alimenticios, San Andres, Sal- azucar Diatraea spp. en la A m e r i c a T r o p i c a l . ( I n Pt.) T u r - vador. Vol.3. San Salvador:Ministerio de Agricultura y rialba 2(1):6-8. Ganaderia. Busoli, A . C . , Gallo, D . , L a r a , F . M . , and Sicci, S . O . 1 9 7 9 . K i n g , A.B.S., and Saunders, J . L . 1984. Las plagas inverte- Influence of the p l a n t i n g t i m e of s o r g h u m ( S o r g h u m bico- bradas de cultivos anuales alimenticios en America Cen- Ior(L.) M o e n c h ) on the incidence of Contarinia sorghicola t r a l . ( I n Es.) Overseas L o n d r e s , M 6 x i c o : Overseas D e v e l - (Coquillet 1898) (Diptera-Cecidomyiidae) and Diatraea opment Administration. saccharalis (Fabricius 1794) (Lepidoptera Pyralidae). (In Pt.) S u m m a r y i n En.) A n a i s d a Sociedade E n t o m o l o g i c a Lacayo, L. 1977. Especies parasiticas de Spodoptera frugi- do Brasil 8(1): 103-113. perda ( S m i t h ) , Diatraea lineolata ( W e r ) y Trichoplusiani ( H b n ) en zonas de M a n a g u a y Masatepe. ( I n Es.) Pages C A T I E (Centro Agronomico Tropical de Investigation y M9.I-M9.28 in Memoria, XXIII Reunion... Alimenticios, Ensenanza). 1986. Alternativa de Manejo para el sistema Panama. Vol.2. Panorma: Instituto de Investigaci6n maiz + m a i c i l l o , T e j u t l a , El Salvador: descripci6n y v a l i d a - Agropecuaria. c i 6 n en fincas pequenas, T u r r i a l b a , Costa Rica. ( I n Es.) Informe Tecnico no.76. Turrialba, Costa Rica:CATIE. Lara, F.M., Barbosa, F.G.C., Busoli, A.C., and Barbosa, J . C . 1979. Behaviour of s o r g h u m genotypes in relation to Cortez, M . R . , Reyes, R., and Alas de Velis, M. 1984. attack by Diatraea saccharalis ( F a b r i c i n s 1794). ( I n Pt. Plagas de los granos basicos y su c o n t r o l . ( I n Es.) Boletin S u m m a r y i n En.) A n a i s d a Sociedade E n t o m o l o g i c a d o D i v u l g a t i v o n o . 12. A n d r e s , La L i b e r t a d , El Salvador: Cen- Brasil 8(1): 125-130. t r o N a c i o n a l de Tecnologia A g r o p e c u a r i a . 57 pp. Mendonca, F.A.F. 1986. M a n e j o integrado de pragas da CENTA (Centro Nacional de Tecnologia Agropecuaria). canadeacucar e tecnologias de p r o d u c a o de parasitoides e 1980. Sorgo ( m a i c i l l o ) Sorghum hicoior (L) Moench. (In entomopatogenos. Curso. Grupo latinoamericano de co- Es.) Pages 21 -28 in Granos basicos y calibraci6n de equipos operacion h o r i z o n t a l en fitosanidad de la cana de azucar. de aspersi6n. Manual Tecnico no.3. San Andres, La Liber - ( I n Pt.). I A A planalsucar, Brasil. R o m e , Italy: F A O 6 2 p p . t a d , E l Salvador: C E N T A . M e z a , S.C., and Koritkowski, G . C h . 1967. Un nuevo F A O . 1986. 1985 F A O P r o d u c t i o n Y e a r b o o k , vol.39. hiperparasito de la mosca Paratheresia claripalpis w u l p ; R o m e , Italy: F A O . parasito del " B o r e r de la cana de azucar" Diatraea saccha- Fuentes, V . J . S . 1983. ICTA 450 Un hibrido de sorgo para ralis Fabr. en el Peru. (In Es.) Revista Peruana de E n t o m o - g r a n o . ( I n Es.) F o l l e t o Tecnico no.27. Guatemala: I n s t i t u t o logia 10(1):16-20. Ciencia y Tecnologia A g r i c o l a . Mihm, J.A. 1984. Tecnicas eficientes para la crianza Geraud, F. 1970. Insectos que atacan al sorgo granero, masive e. infestacion de insectos, en la selecci6n de las S o r g h u m vulgare Pers., en el estado de Z u l i a . Venezuela. plantas de maiz Diatraea sp. ( I n Es.). M e x i c o : C e n t r o ( I n Es.) Revista de la Facultad de A g r o n o r m a (Venezuela) Internacional de Mejoramiento de Maiz y Trigo. 1(3):13C30. Obando, R. 1975. Diatraea lineolata dinamica de poblaci- Harris, K . M . 1985. L e p i d o p t e r o u s stem borers of s o r g h u m . ones y su dano en plantas de maiz, 1975. ( I n Es.) Pages Pages 161-167 in Proceedings of the International Sor- M20.lCM20.19 i n Memoria, XXII Reunion Anual del g h u m E n t o m o l o g y W o r k s h o p , 15-21 J u l 1984, College Sta- Programa Cooperativo Centroamericano para el Mejora- t i o n , Texas, U S A . Patancheru, A . P . 502 324, I n d i a : Inter- miento de Cultivos Alimenticios, San Jose, Costa Rica. national Crops Research Institute for the Semi-Arid V o l 2. San Jos6, Costa Rica: M i n i s t e r i o de A g r i c u l t u r a y T r o p i c s . Ganaderia.

Hodges, R . W . (ed.). 1983. Checklist of the Lepidoptera of O b a n d o , S.R., and van H u i s , A. 1977. Spodoptera frugi- A m e r i c a , N o r t h o f M e x i c o . E.W. Classey, and the Wedge perda J.E. Smith: umbrales permisibles de dano foliar y Entomological Research Foundation. 78 pp. metodos de control quimico en maiz de primera epoca. (I n Es.) Pages M 2 0 . l C M 2 0 . 1 7 in M e m o r i a , X X I I I Reunion Anual del Programa Cooperativo Centramaericano para el Mejoramiento de cultivos Alimenticios, Panama. Vol.2. Panama: Instituto de Investigacion Agropecuaria.

57 Peairs, F.B., and Saunders, J . L . 1980. Diatraca lineolata Sequeira, R.A., Gilstrap, F.E., Andrews, K.L., Meck e n - a n d D. saccharalis: una revision en relacion con el maiz. (In stock, D., and Fuentees, H. 1986. D i n a m i c a de poblaciones Es.) Agronomla Costarricense 4(1) 123-135. de Diatraca lineolata ( W a l k e r ) en sistemas de c u l t i v o s de pequenos agricultores del sur de H o n d u r a s . ( I n Es.) Pages P a u l , C.L.., and de W a l t , B.R. (eds.) 1985. Sorgo en siste- 5 2 . l C 5 2 . 1 0 i n Memoria, XXXII Reunion Anual del Pro- mas d e p r o d u c t i o n e n A m e r i c a L a t i n a . ( I n Es.) M e x i c o : g r a m a C o o p e r a t i v o C e n t r o a m e r i c a n o p a r a e l M e j o r a - C e n t r o I n t e r n a t i o n a l de M e j o r a m i e n t o de M a l z y T r i g o . miento de Cultivos alimenticos, San Salvador, El Salva- Pereira, R . P . , da Costa, R . A . E . , and Ferreira, J . M . 1987. dor, Vol. Sorgo. San Salvador, El Salvador: Centro Incidencia de Diatraca em genotipos de sorgo sacarino em Nacional de Tecnologia Agropeuaria. diferentes epocas de p l a n t i o . ( I n Pt.) Pesquisa A gropecua- Serrano, C.L., Henriquez, M.G., Najera, M.J.A., Reyes, ria Brasileira 22(1): 23-25. R., and Sequeira, R.A. 1986. D e t e r m i n a c i 6 n de la o c u r r e n - Quezada, J . R . 1979. Poblaciones remanentes de barrena- ciade barrenadores Diatraca ( P y r a l i d a e , lepidoptera) y del d o r e s e n cartas de malz. ( I n Es.) San Salvador, El Salvador: nivel de control biol6gico nativo en El Salvador. Inf o r m e U n i v e r s i d a d de El S a l v a d o r , F a c u l t a d de Ciencias y de prgreso. ( I n Es.) Pages 515.1-515.9 in Memoria, XXXII H u m a n i d a d e s . 22 p p . Reuni6n Anual del Proglowa...Alimenticios, San Salva- dor, El Salvador Vol. Sorgo. San Salvador, El Salvador: Quintana, M . V . , and Walker, D . W . 1970. Oviposition C e n t r o N a c i o n a l de T e c n o l o g i a A g r o p e c u a r i a . preference b y g r a v i d sugarcane borer m o t h i n P u e r t o R i c o . J o u r n a l o f E c o n o m i c E n t o m o l o g y 63:987-988. Seshu Reddy, K.V. 1985. Integrated Approach to the Con- t r o l of s o r g h u m stem borers. Pages 205-215 in Proceedings Requena, J.R., and Angeles, N. de J. 1966. N u e v a hosped- of the International Sorghum Entomology Workshop, 15- era de Diatraca saccharalis Fabricius en Venezuela. (In Es. 12 Jul 1984, College Station, Texas, USA. Patancheru, S u m m a r y in Eng) A g r o n o m l a T r o p i c a l 16(1): 101-102. A.P. 502 324, India: International Crops Research Insti - Reyes, R., Andrews, K . L . , Cheng, P . C . , and Garcia, F . A . tute f o r the S e m i - A r i d T r o p i c s . 1983. Un aplicador manual de insecticides granulados: su Shotman, Ch. 1978. C o n t r o l b i o l 6 g i c o de plagas en malz, eficacia par el c o n t r o l de Spodoptera fruqipcrda ( J . E . frijol y sorgo: proposici6n de un programa de investigaci- S m i t h ) and Diatraca spp. c o n p h o x i m en el sorgo, S o r - ones y trabajos. P r o y e c t o C o n t r o l I n t e g r a d o de Plagas. ( I n ghum bicoloren El S a l v a d o r , C . A . ( I n Es. S u m m a r y in Es.) Managua, Nicaragua: Instituto Nicaraguense de Tec- En.) T u r r i a l b a 33(4):375-379. nologia Agropecuaria. 38 pp. Reyes, R., Cea, I.A., Serrano, C.L., Oliva, J.L., Sequeira, Simon, J.E., and Arellano, M. 1959. C o n t r o l del b a r r e n o R., and Browning, H. 1987. l n t r o d u c c i o n y liberacion de Diatraca saccharalis con insecticidas organicos. (In Es.). Cotcsia flavipes C a m . ( B r a c o n i d a e : H y m e n o p t e r a ) en el Revista Peruana de Entomologla 2(1):81-83. c o n t r o l b i o l o g i c o de gusanos barrenadores del tallo Dia- traeaspp. en malz y sorgo asociado en El Salvador. ( I n Es.) Teetes, G.L., Young, W.R., and Jotwani, M.G. 1980. Page Resumenes, 332 in Reuni6n Anual del Programa Insect pests of s o r g h u m . Pages 17-40 in Elements of inte- Cooperativo Centramericano para el Mejoramiento de grated control of sorghum pests. FAO Plant Production Cultivos Alimenticios, Guatemala. Guatemala: Institut o a n d P r o t e c t i o n Paper n o . 19. R o m e , I t a l y : F A O . de Ciencia y tecnologia A g r i c o l a . Viana, P.A. 1985. Sorghum insect problems in Brazil. R u i z , M . G . A . , and Koritkowski, C h . 1975. Insecticidas Pages 97-101 in Proceedings of the International Sorghum g r a n u l a d o s aplicados al suelo p a r a el c o n t r o l de Diatraca Entomology Workshop, 15-21 Jul 1984, College Station, saccharalis en sorgo. ( I n Es.) Revista Peruana de E n t o m o - Texas, USA. Patancheru, A.P. 502 324, India: Interna- logla 18(1):117-119. t i o n a l C r o p s Research I n s t i t u t e f o r the S e m i - A r i d T r o p i c s .

Sarmiento, M . J . 1981. Las plagas del maiz. ( I n Es.) In Yount, O. 1984. S t e m borers a t t a c k i n g Sorghum bicolor S e g u n d o C u r s o I n t e n s i v o de C o n t r o l I n t e g r a d o de Plagas y ( L . ) M o e n c h and Zca mays L. in the Texas l o w e r R i o Enfermedades Agricolas 2-27 Feb 1981, La Molina, Lima, Grande Valley. M.S. thesis. Texas A & M University, Col- P e r u . V o l . 2 . L i m a , P e r u : U n i v e r s i d a d N a c i o n a l A g r a r i a L a lege Station, Texas, USA. 83 pp. M o l i n a , T o m 2 , Fascicula 33, 17pp.

Sequeira, D . A . , D a x l , R., Sommeijer, M . , van Huis, A . , and Pedersen, F. 1976. Guia de control integrado de plagas de m a l z , sorgo y f r i j o l . P r o y e c t o C o n t r o l I n t e g r a d o de plagas. (In Es.) MAG-FAO-PNUD. Managua, Nicaragua: Instituto Nicaraguense de Tecnologia Agropecuaria. 47 p p .

58 D i s c u s s i o n rienced by A f r i c a n farmers due to stem borer damage? Wightman: Is the t a x o n o m y of stem borers ade- Sithole: In Z i m b a b w e , borer infestation levels in quately known? farmers' fields varies from 15-40%, but information Harris: Authoritative taxonomic revisions of the on real yield loss is not k n o w n . main genera have been published: on Diatraea: Seshu Reddy: Some of the farmers in Kenya are Tarns and Bowden on Busseola and Sesamia; and aware of the extent of damage or losses caused by Bleszynski on Chilo and Acigona. So the species are stem borers, but most are not. Farmers are being therefore recognized as good, morphologically sepa- educated on this aspect, on the reduction of food rate taxa, although K a u f m a n n has suggested sub- losses through pest management strategies, and speciation of B. fusca in Nigeria. If there are any about the use of small-scale and low-cost f a r m instances where there is good evidence to suggest the equipment. need f o r further t a x o n o m i c research it should be Sharma: Since deadheart f o r m a t i o n is the most undertaken. important component of yield reduction, to what Seshu Reddy: The distribution of stem borers and extent was deadheart f o r m a t i o n observed in f a r m - their incidence should be thoroughly worked out. ers' fields? The time of attack by the stem borers in relation to Sithole: In farmers' fields deadheart formation is crop phenology and the density of borer population normally less than 20%, but varies f r o m season-to- at the time of attack are important factors in crop season. loss assessment. Nwanze: Does anyone k n o w why stem tunneling Leuschner: In A n d h r a Pradesh, India, farmers make does not appear to be correlated w i t h grain yield? use of crop residues to the m a x i m u m extent. This is a Are we fully conversant w i t h borer biology and good cultural practice which reduces the carryover behavior? What is happening when low borer infes- population. Usually there is little carryover because tations result in increased grain yield? livestock consume the residues. Leuschner: Stem tunneling on fully expanded inter- Nwanze: The distribution of stem borers of sorghum nodes is not important. Attack on unexpanded and pearl millet in West A f r i c a was f o u n d to be internode below the immature head can cause d a m - associated w i t h rainfall patterns. B. fusca was found age such as poor head exsertion or chaffiness. south of latitude 11° 30 ' in B u r k i n a Faso where rain- Vidyabhushnam: The most serious damage caused fall was over 900 m m . Above this latitude and in the by stem borers is through peduncle boring. The n o r t h , in the driver regions of the Sahel, B. fusca was shorter peduncle types are apparently prone to replaced by A. ignefusalis. The same pattern was higher damage. Has any scientific study been con- also noticed in northern Nigeria. ducted to establish the relationship between pedun- Tabo: It has been mentioned that in southern Africa, cle length and borer incidence? in Z i m b a b w e , f o u r important stem borers are dis- Taneja: We have noticed that in West A f r i c a even tributed according to latitude. W o u l d y o u suspect lines w i t h long peduncles have shown considerable temperature, rainfall or interaction of these t w o to ear shedding. be the most likely and i m p o r t a n t factor affecting the Leuschner: In that situation, it is not peduncle length incidence of stem borers? but diameter of the peduncle in relation to head size Sithole: The relative distribution of these f o u r stem that should be considered. borers is probably related to rainfall patterns, tem- Singh: O u r observations and results indicate that perature, relative h u m i d i t y , and elevation above sea long peduncle types suffer more damage w i t h higher level, or the interaction of some of these factors. numbers of holes, larvae and pupae, tunnel length, Srivastava: Is there any relationship between alti- and percent stem tunneling. Studies on inheritance tude and environmental conditions on the distribu- of peduncle and stalk resistance also indicated that tion of B. fusca? these were independent while the number of holes Sithole: In southern A f r i c a , B. fusca is most preval- and degree of tunneling in stem (stalk and pendun- ent at higher elevations ( > 9 0 0 m) which are cool and cle) are governed by nonadditive genes, the heritabil- receive high rainfall. The incidence of this species is ity was however, low. lowest at lower elevations ( < 7 0 0 m) which are w a r m Shinde: Not all sorghum entries which show leaf and receive low rainfall. injury produce deadhearts. In such cases how does Pawar: H o w much damage has been generally expe- one estimate the intensity of damage? Varieties

59 s h o w i n g dcadhearts in one location do not produce various practices needs to be precisely understood in dead hearts in other parts of the state. W h a t could be order to develop an effective I P M package f o r c o n - the reason? trolling stem borers. Seshu Reddy: Deadheart f o r m a t i o n depends on the Lavigne: W h a t chemicals are the best f o r the c o n t r o l density of borer p o p u l a t i o n , time of attack, and of Diatraea in central and southern America? -1 mode of larval entry in the plant. Damage intensity Reyes: C h l o r p y r i f o s 2.5 g (13 kg ha ), phoxim 2.5g -1 can be estimated f r o m the number of plants d a m - (12 kg ha ), and Trichlonfon, Metaniclofos 600 (1.4 -1 aged, or by scoring the damage on individual leaves 1 ha ). A p p l i c a t i o n is recommended 20-30 days after and t a k i n g an average f o r the plant. It is a fact that plant emergence and before booting. deadheart f o r m a t i o n w i t h i n a region may occur in Gadalla: W h a t chemicals are used to c o n t r o l stem one location and not in another. Even adjascent borers in southern Africa? W h a t degree of success fields may show quite distinct levels of infestation. has been obtained in terms of field gain? This is due to the borer p o p u l a t i o n prevalent in an Sithole: Carbofuran, endosulfan, carbaryl, trichlor- area and the time of attack in relation to the phenol- f a n , and synthetic pyrethroids are used in commer- - 1 ogy of the crop. cial farms and sorghum grain yields of up to 5 t ha Gold: Given the limitations of cultural practices as are obtained. In resource-poor farmers' fields, the - 1 evolved by small farmers and that they are not suc- yield is generally less than 1 t ha where chemical cessful in c o n t r o l l i n g pests, it is i m p o r t a n t to con- c o n t r o l of stem borers is not practiced. sider the change in insect populations in different Hussain M a o Haji: ICRISAT distributes interna- intercropping trials. Is there any reduction in stem t i o n a l nurseries t h r o u g h o u t the S A T . These are not borer damage as a result of intercropping? attractive lines and it is impossible to use the resis- Seshu Reddy: Under sorghum/cowpea intercrop- tant lines in our breeding programs. What purpose ping it was observed that there is increased activity then is this distribution to national programs, and of natural enemies. The crop m i x t u r e appears to how can they make use of these lines? affect the visual stimuli and orientation of different Taneja: The purpose of sending these nurseries is insects. twofold: first, to test the stability of resistance across Pawar: Research in India and A f r i c a has shown that environments, and second promising breeding lines c u l t u r a l practices have good pay o f f provided they are included in these nurseries, w h i c h can be directly are followed synchronously by farmers. used in the national programs if they f i n d them Nwanze: M o s t of the cultural practices exercised by useful. farmers have evolved over time. The role of these

6 0 Bionomics and Control (Except Host-plant Resistance)

Bioecology of Sorghum Stem Borers

K.M. Harris1

Abstract

The evolution and significance of the stem boring habit in Lepidoptera is reviewed, with particular reference to the main genera with larvae that are specialized borers in the stems of Gramineae. Important elements of the biology and ecology of sorghum stem borers are summar• ized, including host-plant associations and geographical ranges, and the main interactions between adult and larval sorghum stem borers and their host plants are reviewed to determine their relevance in pest epidemiology and the development of effective control measures.

Introduction of the more primitive families (e.g. Hepialidae, Cos- sidae) feed in concealed situations in the soil or as D u r i n g the evolution of the Lepidoptera, the special- borers, leaf-miners, leaf-tiers or case-bearers and ized larval habit of feeding in stems of Gramineae that larvae feeding in exposed positions on plants, and Cyperaceae developed as part of the complex such as the many leaf-feeding species, usually belong interaction between this major Order of insects and to the more advanced families of Lepidoptera (Riek flowering plants. The earliest fossil insects date f r o m 1970). the Upper D e v o n i a n , about 360 m i l l i o n years ago The Gramineae, as with the Lepidoptera, evolved but the Lepidoptera evolved much more recently. comparatively recently, probably originating in the Their earliest k n o w n fossils date f r o m the Eocene, Mesozoic, with the earliest known fossils dating about 60 m i l l i o n years ago. W i t h the exception of a f r o m the late Tertiary, about 25 m i l l i o n years ago. few carnivorous groups whose larvae feed mainly as ( G o u l d and Shaw 1983). Both groups have been predators on scale insects and mealybugs, most highly successful in evolutionary terms. Gramineae lepidopterous larvae are phytophagous. The plants are currently represented by about 7500 species, and on w h i c h they feed are mainly angiosperms, which Lepidoptera by 200000 species. first appear in the fossil record in the early Cretace- Strong interactions between Gramineae and Lepi- ous, about 135 m i l l i o n years ago. Phytophagous doptera have evolved over at least the past 25 million larvae may be general or specialist feeders on roots, years and, as a result, the specialized habit of stem stems, bark, branches, twigs, leaves, buds, fruits, b o r i n g in grasses has developed in the f o l l o w i n g seeds, or galls. It is generally considered that larvae main groups:

1. Commonwealth Agricultural Bureau International (CAB1), Institute of Entomology, 56 Queen's Gate, London, SW7 5JR, UK.

ICRlSAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, I C R l S A T Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

63 Pyralidae to Indonesia and T a i w a n . It first appeared in East A f r i c a in the early 1950s and has n o w spread as far as Crambinae Coniesta, Chilo, Diatraea, etc. northern Sudan, Botswana, and Zaire (Ingram Pyraustinae Ostrinia 1983) and may have spread westward f r o m the Galleriinae Eldana Sudan to West A f r i c a . Phycitinae Elasmopalpus, Maliarpha, Emmalocera Schoenobiinae Scirpophaga, Schoenobius, Rupela, etc. Host Plants

Sorghum, maize, pearl, foxtail and finger millets, Noctuidae wheat, sugarcane, and rice are the m a i n cultivated hosts attacked. W i l d grass hosts include Sorghum Amphipyrinae Busseola, Sesamia, Manga, Poeo- halepense, S. verticilliflorum, Panicum maximum, noma, etc. and Pennisetum purpureum.

Castniidae Adult Biology and Ecology Castnia Neupane et al. (1985) have published a recent Against this evolutionary b a c k g r o u n d , the devel• account of this species in Nepal, including observa• o p m e n t of stem b o r i n g on cultivated sorghum and tions on adult activity, and have commented on other cereal crops is comparatively recent. The crop previously published observations f r o m I n d i a and itself is p r o b a b l y not more t h a n about 5000 years East A f r i c a . Details vary w i t h location, due to cli• o l d . The m a i n sorghum varieties cultivated today are matic and other factors, and the f o l l o w i n g general even more recent, and probably differ substantially account should be supplemented by reference to in physical and chemical attributes f r o m their w i l d relevant local information, when necessary. grass precursors. A d u l t s emerge f r o m pupae in stems d u r i n g the late M o s t of the i n f o r m a t i o n that is available on the afternoon and early evening and are active at night. biology and ecology of sorghum stem borers relates D u r i n g the day they are inactive, resting on plants to crop hosts (sugarcane, maize, sorghum, rice, and and plant debris and, because of their cryptic colora• pearl millet) rather than to n o n c r o p hosts, w h i c h are t i o n , are seldom noticed unless disturbed. Females mainly grasses. This i n f o r m a t i o n has been summar• release pheromones to attract males and mate soon ized in general reviews of sorghum pests ( Y o u n g after emergence. The components of the female 1970, Y o u n g and Teetes 1977), and in specialized pheromone have been identified by Nesbitt et al. reviews on lepidopterous stem borers (Jepson 1954) (1979) as (Z)-11-hexadecenal and (Z)-11-hexadecen- and on sorghum stem borers ( H a r r i s 1985). An 1-01 and some w o r k on the use of pheromones to extensive bibliography, with informative abstracts, m o n i t o r this species has been done at I C R I S A T is available in C A B A n n o t a t e d Bibliography E. 105, ( C a m p i o n and Nesbitt 1983). Stemborers of S o r g h u m 1973-87, issued by the C A B On 2-3 consecutive nights, females locate suitable International Institute of E n t o m o l o g y ( C I E ) . The host plants and lay about 10 batches of 10-80 over• f o l l o w i n g accounts of the major pest species h i g h • lapping eggs on the underside of leaves, mainly near light some of the more i m p o r t a n t elements of that the midribs. A d u l t s are generally shortlived (2-5 i n f o r m a t i o n , w i t h emphasis on recent published days) and do not seem to diseperse far f r o m emer• w o r k and key references. gence sites, although there are records of movements of up to a few kilometers. There is no evidence of migration over substantial distances, although the Chilo partellus (Swinhoe) spread of this species in A f r i c a d u r i n g the past 30 years may have resulted from adult dispersal flights. Distribution Mechanisms of host location and identification have not been adequately researched, although some This is the most i m p o r t a n t stem borer of sorghum in w o r k has been done recently. Chadha and R o o m e Asia and parts of Africa. It occurs throughout the (1980) studied oviposition behavior of C. partellus Indian subcontinent and throughout Southeast Asia on maize seedlings. O v i p o s i t i o n started about one

6 4 h o u r after d a r k and batches of 10-200 overlapping Chapman et al. (1983) observed larval survival eggs were laid in a precisely ordered sequence, paral- and dispersal on t w o sorghum cultivars in I n d i a lel to the long axis of the leaf. Contact w i t h the leaf d u r i n g the first six days after hatching. In a series of surface by antennae, ovipositor t i p , and possibly the f o u r experiments, 2 0 - 5 0 % of the larvae were present tarsi, were all involved in choice of the oviposition in the leaf whorls w i t h i n six hours of hatching. By site. E x a m i n a t i o n of the ovipositor tip by light, the t h i r d day, virtually all surviving larvae were in scanning and transmission electron microscopy leaf whorls, but mostly in plants other than those on identified t w o pairs of chemoreceptor sensilla among w h i c h they had hatched. One day after hatching on many mechanoreceptor sensilla. These sensilla may small plants (25-40 cm tall) about half of the larvae prevent oviposition on surfaces that are chemically had moved to adjacent plants. The number of larvae h a r m f u l to the eggs but it was noted that, in the present in plants declined d u r i n g the first three days absence of smooth plant surfaces, eggs are deposited but then stabilized. on other smooth surfaces, even glass, polyethylene, Subsequent instars tunnel into the stem tissue of metal or plastic indicating that the ovipositing the host plant. Singh and Rana (1984) reported female seems indifferent to the suitability of the detailed laboratory and field studies of oviposition, surface as f o o d for its larvae. However, Chapman larval development and pupal weights on 70 sor- and Woodhead (1985) noted that if plant leaves are g h u m cultivars and correlated these parameters with present they are preferred as oviposition sites, so symptoms of field damage (deadhearts, number of there must be some measure of recognition and pref- holes/tunnels and percent tunneling). They con- erence. They also note that b r o w n , dry leaves are cluded that ovipositional nonpreference and antibi- preferred to green, turgid leaves. osis act together to determine the degree of resistance, but that antibiosis has the greater effect. Antibiosis was expressed in slower larval develop- Larval Biology and Ecology ment, higher larval mortality, and lower pupal weights. Antibiosis factors operated in leaf and stem Larvae emerge after about 4 8 days, hatching f r o m tissues. In the absence of these factors, larvae gener- early m o r n i n g before sunrise to around 0800 h. The ally developed faster and produced heavier pupae larvae then climb up young sorghum plants within when fed exclusively on leaf w h o r l tissues rather the first 2-3 hours after hatching and enter the leaf than on stem tissues. w h o r l , where they settle to feed on young leaf tissues. After 2-4 weeks, nondiapause larvae pupate in the The mechanisms determining this behavior and the galleries that they have excavated in the stems. factors affecting survival have been studied in detail Adults emerge f r o m pupae about 5-12 days later. in recent years ( C h a p m a n et al. 1983, Bernays et al. W h e n climatic conditions are favorable, the life 1983, and Bernays et al. 1985). On hatching, larvae cycle is completed in about 25-50 days. Up to five or are positively phototaxic and move upwards f r o m more successive generations may develop annually. hatching sites on the lower leaves. This phototactic D u r i n g cold a n d / o r dry seasons, larvae enter dia- response is quickly lost under the influence of host pause in stems and stubble for up to six months. o d o r and darkness, as larvae approach the leaf When conditions become favorable for further devel- w h o r l . These reactions usually ensure that most lar- opment, they pupate. The factors breaking diapause vae q u i c k l y become established in the w h o r l . Posi- do not seem to have been adequately studied. tive phototaxis is also modified when larvae stray f r o m the stem onto the leaves d u r i n g their upward movement. Contact w i t h a leaf edge usually results Population Dynamics in d o w n w a r d movement until a larva regains the stem; it then continues to move upwards. There are Information on factors that determine population additional directional cues in leaf structure, includ- dynamics of C. partellus on sorghum crops, or in ing large veins and distally directed spines. Leaf other crop ecosystems, is available in various publi- waxes and plant odors also seem to have some cations but has not been fully integrated into effects on the behavior of first instar larvae. Since research programs. Climate and host availability/ successful establishment of early instars on young suitability must be important, as must mate loca- plants mainly determines deadheart incidence and tion, host location, ovipositing success, and first- subsequent yield losses, these studies are very impor- instar larval survival and establishment. The many tant in elucidating useful resistance mechanisms. causes of mortality must also be important, includ-

65 ing physical, chemical and biological factors, that (1943), van Rensburg (1980); Zimbabwe—Smithers operate on egg, larval, pupal and adult stages. M a n y (1960a, 1960b); Tanzania-Swaine( 1957); Uganda- pathogens, predators, and parasites are k n o w n but Ingram (1958); and Nigeria—Harris (1962, 1963), their significance in regulating C. partellus popula- and Usua (1970, 1974). In a d d i t i o n , K a u f m a n n tions is not. (1983) published a paper on f o o d plant adaptations I n g r a m (1983) reviewed w o r k on the biological of different populations in Nigeria, and Adesiyun c o n t r o l of this species in Pakistan and East A f r i c a . (1983) has recorded the effects of intercropping on Apanteles flavipes (Cameron)became an important this species, also in Nigeria. parasitoid in Pakistan after its introduction and Adults emerge f r o m pupae in stems and stubble release f r o m Japan ( A l a m et al. 1972), but similar d u r i n g the evening and are active at night, resting on introductions of A. flavipes and other parasitoids plants and plant debris d u r i n g the day. As w i t h most f r o m India to East A f r i c a failed to establish ( I n g r a m stem borer adults, they only fly d u r i n g the day if 1983). Research on A. flavipes in Pakistan by disturbed. Females release a pheromone soon after M o h y u d d i n et al (1981) showed that strains of the emergence to attract males, and the components parasitoid are attracted to the frass of a particular have been identified as (Z)-11-tetradecenyl acetate stem borer, feeding on a particular host plant. and (E)-11-tetradecenyl acetate by Nesbitt et al. Six other species of Chilo have been reported on (1980) and H a l l et al. (1981). sorghum in various parts of the w o r l d (Seshu Reddy D u r i n g the 3-4 nights f o l l o w i n g emergence, fe- 1985). These are of m i n o r importance compared to males lay eggs in batches of 30-100 under the vertical C. partellus. edges of leaf sheaths, laying a total of about 200 eggs per female, van Rensburg et al. (1987), working with maize, observed that the sheath of the youngest Busseola fusca ( F u l l e r ) unfolded leaf is most attractive for oviposition and that egg laying is concentrated on plants that are less Distribution than 8 weeks o l d . They also recorded that the egg batches of spring moths were smaller than those of This is the most widespread stem borer of sorghum summer moths, possibly because the body reserves in A f r i c a south of the Sahara. It has been reported in of spring moths are smaller. most countries f r o m Guinea in the west to Somalia in the east, and southward to South Africa. It is a Larval Biology and Ecology major stem borer of sorghum in Burkina Faso. but does not occur n o r t h of latitude 11° 3 ' N , although it Larvae hatch about a week later and disperse over occurs as far n o r t h as 12° 6' N in Nigeria (Nwanze plants before entering the leaf whorls to start feed- 1985). ing. Presumably their behavior is similar to that of C. partellus first-instar larvae, but there do not seem to have been any detailed recent studies of B. fusca Host Plants on sorghum, van Rensberg et al. (1987), working w i t h maize, recorded that 8 1 % of lavae up to the Maize, on which B. fusca is an important pest, f o u r t h instar were f o u n d in leaf whorls. F i f t h instars s o r g h u m , sugarcane, and, to a lesser extent, pearl were more evenly distributed in the plants. Sixth millet are all host plants. W i l d grasses such as instars were found in considerably larger numbers Sorghum verticilliflorum, Pennisetum purpureum, than the previous instars in the stems and ears. The Hyparrhenia rufa, and Panicum maximum are also number of f i f t h instar larvae reached a peak at 8 host plants. weeks after plant emergence, and only sixth instar larvae were found in stem bases, due to the c o m - Adult Biology and Ecology mencement of diapause in later plantings. They also noted that the extent of larval migration within van Rensburg et al. (1987) have published the most crops was underestimated by earlier workers, since recent account of the ecology of B. fusca, based on at least 4% of the total number of larvae in a planting their w o r k in South A f r i c a , and refer to earlier pub- migrated to adjacent plants directly after hatching. lications on the biology and ecology of this species. The average number of larvae per infested plant Key references given in their bibliography inlcude: changed continually due to migration d u r i n g crop South A f r i c a — M a l l y (1920), du Plessis and Lea development.

6 6 Larval development generally takes 24-36 days bibliography covering the period 1887-1980 that before pupation in plant stems or stubble. Adults contains 1193 citations. M o r e recent w o r k has been emerge about 9-14 days after pupation and the life abstracted in C A B A n n o t a t e d Bibliography E.49, cycle in favorable conditions is completed in about Diatraea saccharalis 1973-87 issued by the C A B 7-8 weeks. In dry a n d / o r cold conditions, larvae International Institute of Entomology. enter diapause for six months or more and diapause D. saccharalis is the commonest and most wide- is broken d u r i n g subsequent rains. Usua (1970) stud- spread of the many species of Diatraea that occur in ied diapause in detail on maize in southern Nigeria North, Central, and South America, with a range and reported that diapausing larvae are present extending from Louisiana, North Carolina, and throughout the year, irrespective of the condition of Texas through Mexico, Central America, and the the host plant, but w i t h peak incidence in July and Caribbean southward to Argentina ( C I E D i s t r i b u - December. He concluded that the presence of water t i o n M a p 5). Sugarcane is the main host plant but does not terminate diapause in the field. In a later this species also develops on maize, sorghum and paper on the physiology of diapause and nondia- rice, as well as on Johnson grass (Sorghum hale- pause larvae, Usua (1974) concluded that the main pense). Pampas grass (Cortaderia selloana) and factor enabling diapause larvae to survive adverse other grasses, including Cymbopogon citratus and conditions appears to be their efficient water conser- C. nardus. vation mechanism. Harris (1962), reporting studies A detailed, illustrated account of this species in of this species in northern Nigeria, where rainfall the United States was published by H o l l o w a y et al. ceases completely d u r i n g the five-month dry season, (1928) and is probably still the best overall account observed that diapause was terminated at the end of of its biology and ecology, w i t h detailed descriptions the dry season when larvae drank water. Larvae that of life stages and damage symptoms. There are had been kept in dry sorghum stems in a laboratory obvious similarities w i t h Chilo partellus. Oviposi- for five months drank immediately when given t i o n starts at dusk and continues d u r i n g the 3-4 access to drops of distilled water; their weight nights f o l l o w i n g adult emergence. Batches of up to increased by 2 0 - 4 0 % w i t h i n 24 hours, indicating 50 eggs are laid on upper or lower surfaces of leaves rapid rehydration, and they pupated w i t h i n a week. in overlapping, generally elongated clusters. After A control set of larvae maintained in a humid 4-9 days larvae hatch, and, for the first week, often atmosphere did not increase in weight and did not feed w i t h i n the leaf-sheath or between the leaf- show any marked tendency to pupate, van Rensberg sheath and stem. They then tunnel into the stems to et al. (1987) noted that there is no clear understand- feed, and eventually pupate, after first preparing exit ing of the factors inducing diapause, although it may holes. The life-cycle f r o m egg to adult is usually be under genetic c o n t r o l , as suggested by Usua completed in 35-50 days when conditions are favor- (1970), and that it is still uncertain which factors are able. In tropical areas, continuous development may responsible for breaking diapause. They also noted produce as many as seven generations annually. In that unpublished w o r k suggests that free water will the n o r t h e r n and s o u t h e r n parts of its range, advance pupation by a m a x i m u m of one week. F r o m D. saccharalis larvae enter diapause in the winter their o w n observations, it appears that diapause lar- and carryover to the f o l l o w i n g season in crop vae must pass a specific period under specific condi- residues. tions before certain physical conditions will induce Pheromone studies w i t h this insect have been pupation. reviewed by H a m m o n d and Hensley (1971) and A second species of Busseola of minor impor- other aspects of its biology and ecology that have tance, B. segeta Bowden, occurs on sorghum, maize, been studied in recent years include: the influence of finger millet, sugarcane, and various grasses in climatic factors (Mendes 1978); the height and time Uganda and Tanzania. I n g r a m (1958) published a of adult flight in Brazil (Mendes et al. 1978); sea- brief account of its biology in Uganda. sonal abundance in Texas (Fuchs and H a r d i n g 1979); induction and termination of larval diapause in Texas (Fuchs et al. 1979); fluctuations of adult Diatraea saccharalis (Fabricius) populations in Brazil (Teran 1979); larval density and the effects of parasites and pathogens in Brazil Because of its importance as a pest of sugarcane, the (Teran 1983); and laboratory studies of oviposition literature on D. saccharalis is substantial and mainly and development in Brazil ( B o r t o l i and M a n p r i m relates to that crop. Roe et al. (1981) published a 1984).

67 Other species of Diatraea that attack sorghum, attacks crops opportunistically when they have mainly D. lineolata (Walker), D. grandiosella ( D y a r ) replaced its natural hosts. It is principally a pest on and D. crambidoides (Grote), have not been studied sugarcane and details of its life history, develop- to the same extent as D. saccharalis. ment, and behavior on that host plant in Ghana have been published recently by Sampson and K u m a r (1985). In Ghana, mated females laid about 300-350 Coniesta ignefusalis ( H a m p s o n ) eggs over a four-day period, in batches, mainly under leaf sheaths. Eggs hatched after 5-7 days and Harris (1962) published a detailed, illustrated ac- early instar larvae dispersed d u r i n g the first three count of the biology of this species in Nigeria. ln a days before settling to tunnel into stems. Larval review on pests of pearl millet in West A f r i c a , development lasted about 31 days, followed by G a h u k a r (1984), included references to t w o subse- p u p a t i o n in bored stems f o r 7-13 days, and the q u e n t p u b l i c a t i o n s on this species in Senegal. life-cycle was completed in 36-62 days. G i r l i n g C. ignefusalis is k n o w n to occur across the Sahel belt (1978) reported observations on the distribution and of West A f r i c a f r o m Senegal t h r o u g h Niger and biology of this species in Uganda and also assessed northern Nigeria to Chad. Its preferred host plant is its crop pest status in Ghana ( G i r l i n g 1980). A t k i n - pearl millet but larvae also feed on sorghum, espe- son (1980) reported its biology, distribution, and cially when it is intercropped w i t h millet, and on natural host plants in South A f r i c a . Nwanze (1985) maize and some wild grasses, including Pennisetum recorded that this is the predominant borer on purpureum. sorghum d u r i n g August and September in B u r k i n a At Z a r i a , Nigeria, Harris (1962) observed that Faso but it appears to be restricted below latitude adults emerged f r o m pupae in stems between 1900 12°N in b o t h B u r k i n a Faso and Nigeria. and 2300h in a caged experiment. B o t h sexes flew w i t h i n three hours of emergence and mated either on the night of emergence or early the f o l l o w i n g night. Sesamia Species Eggs were laid between the leaf sheath and stem, in batches of 20-50, w i t h up to 200 eggs laid per female At least eight species of Sesamia have been recorded in captivity. Larvae hatched after 12 days and at first as stem borers of sorghum, mostly in A f r i c a but also remained clustered under the leaf sheaths, but within in Europe, Asia and the Pacific. Their geographical 24 hours they started to tunnel into the leaf sheaths ranges have been summarized by Harris (1985) and and underlying stems. They d i d not disperse over the Seshu Reddy (1985). S. calamistis Hampson is plant or concentrate in leaf whorls but dispersed probably of greatest overall importance in Africa t h r o u g h the plants partly by active tunneling and south of the Sahara, where S. botanephaga Tarns partly by u p w a r d movement in the leaf sheaths as and Bowden, S. nonagrioides (Lefebvre), S. poe- they grew. Some larval migration occurred between phaga Tarns and Bowden, S. penniseti Tarns and plants but the m a x i m u m spread f r o m k n o w n ovipo- B o w d e n and 5. albivena H a m p s o n also occur. sition sites was 1.2 m in the insectary and 1.8 m in the S. cretica Lederer is present in Ethiopia, Somalia, field. D u r i n g the wet season larvae completed devel• Sudan and the western Mediterranean and S. infer- opment in 30-40 days, p u p a t i o n lasted 7-13 days, ens (Walker) occurs in the Indian subcontinent. and three generations developed with an average Southeast Asia, and as far east as the S o l o m o n life-cycle of about 57 days. T o w a r d the end of the Islands. wet season, larvae entered diapause and carried over Host ranges of these species are generally similar, in dry stems and stubble u n t i l the end of the 5-6 including maize, sorghum, pearl millet and other m o n t h dry season. millets, and various grasses. Accounts of the biology The N o r t h A me ri c a n species, Eoreuma loftini of the species vary in the amount of detail available ( D y a r ) , is related to C. ignefusaJis but is mainly a but i n f o r m a t i o n on S. calamistisis probably typical. pest of sugarcane. It seems to be of relatively low In Uganda, I n g r a m (1958) recorded that batches of importance as a stem borer of sorghum. up to 20 eggs were laid under leaf sheaths, as in the case of B. fusca, w i t h females laying about 300 eggs each, over 2-3 nights. Eggs hatched 7-9 days later Eldana saccharalis (Fabricius) and first-instar larvae bored straight into the stems, I n g r a m (1983) records that this A f r i c a n species is w i t h only occasional feeding in the leaf w h o r l , in p r i m a r i l y a borer of Cyperus species and probably marked contrast to the behavior of first-instar

68 B. fusca larvae. Some larvae migrated to other all continents as a first step to determining the extent plants d u r i n g development, which t o o k 27-36 days of the problems and in f o r m u l a t i n g proposals f o r the in the laboratory. The life-cycle in the laboratory prompt exchange of scientific and technical infor- was completed in 45-58 days and breeding c o n - m a t i o n and f o r c o o r d i n a t i n g some of the principal tinued throughout the year, without any larval dia- lines of w o r k " . This W o r k s h o p may represent the pause. Harris (1962) recorded similar details of the first step in that direction, for sorghum stem borers, biology of this species in Nigeria and confirmed that, more than 30 years later. despite the severe dry season, there was no larval Some research workers may accept a pragmatic diapause and the species continued to develop approach, and maintain that rigorous and extensive throughout the year. selection and breeding f o r host-plant resistance w i l l I n g r a m (1958) r e c o r d e d t h a t the l a r v a e o f eventually provide acceptable practical solutions to S. poephaga enter the stem t h r o u g h the leaf w h o r l , stem borer problems. I accept that host-plant resis- so differing f r o m S. calamistis, but Harris (1962) tance does offer the most feasible long-term solu- reported that in Nigeria they bored directly into the tions f o r m u c h of the tropics but am convinced that a stems under the leaf sheaths. There is obviously better entomological understanding of the biology scope for further study as this is an i m p o r t a n t differ- and ecology of the pest species w i l l result in improved ence in behavior that must affect mortality factors resistance and better overall pest management. That and c o n t r o l . There seems to have been little recent will require more and better-organized information research on either S. calamistis or S. poephaga but on key aspects: the extent of adult dispersal/migra- a few post-1972 papers refer to S. inferens and tion; mate location; courtship behavior; host loca- S. nonagrioides. tion and selection; oviposition site selection; larval behavior; mortality factors; and population dynamics. As Y o u n g and Teetes (1977) emphasized, unique O t h e r S o r g h u m S t e m B o r e r s pest management systems are required f o r each distinct agroecosystem. Generalization is useful up to a Elasmopalpus lignosellus (Zeller) is a m i n o r pest of p o i n t , but there is no substitute f o r accurate and sorghum in N o r t h , Central, and South America; detailed information. Ostrinia furnacalis Guenee has been recorded f r o m sorghum in Japan and Ostrinia nubilalis Hubner, the European corn borer, occasionally attacks sor- g h u m in N o r t h America. None of these species seems R e f e r e n c e s sufficiently i m p o r t a n t to merit in lusion in detail in this review. Adesiyun, A.A. 1983. Some effects of intercropping of sorghum, millet and maize on infestation by lepidopterous stalk-borers, particularly Busseola fusca. Insect Science Conclusions and its Application 4(1-2):387-391. A l a m , M . M . , Beg, M . N . , Ghani, M . A . , a n d Watanabe, C . F r o m the above accounts of the main species of 1972. Introduction of Apanteles spp. against graminaceous sorghum stem borer, it is clear that much i n f o r m a - borers into Pakistan. Technical Bulletin, Commonwealth tion is available on their biology and ecology, but it Institute of Biological Control 15:1-10. has been obtained mainly by individual research Atkinson, P.R. 1980. On the biology, distribution and workers operating in piecemeal fashion over the past natural host-plants of Eldana saccharina W a l k e r ( L e p i - 50 years. There has been no clearly integrated doptera: Pyralidae). Journal of the Entomological Society approach t o w a r d an understanding of the ecology of Southern Africa 43:171-194. and epidemiology of the main species that w o u l d Bernays, E., Chapman, R.F., and Woodhead, S. 1983. assist the development of effective pest manage- Behaviour of newly hatched larvae of Chilo partellus ment. One possible exception is the w o r k on Dia- (Swinhoe) (Lepidoptera: Pyralidae) associated with their traea saccharalis in the U S A and South A m e r i c a , establishment in the host-plant, sorghum. Bulletin of E n t o - but that relates to sugarcane, not sorghum. mological Research 73:75-83.

Jepson (1954), concluding his review of the w o r l d Bernays, E., Woodhead, S., and Haines, L. 1985. C l i m b i n g literature on lepidopterous stem borers of tropical by newly hatched larvae of the spotted stalk borer Chilo graminaceous crops, suggested "the creation of a partellus to the t o p of s o r g h u m plants. E n t o m o l o g i a E x p e - small international sub-committee of workers f r o m rimentalis et Applicata 39:73-79.

6 9 Bortoli, S.A. de, and M a n p r i m , M . C . 1984. Aspectas b i o - Harris, K . M . 1962. Lepidopterous stem borers of cereals in logicos do broca da cana-de-acucar, Diatraea saccharalis Nigeria. Bulletin of Entomological Research 53:139-17 1 . (Fabricius, 1794) (Lepidoptera Pyralidae), cm milho (Zea Harris, K . M . 1963. Annual variations of dry-season popu- mays L.) sob condicoes de l a b o r a t o r i o . ( I n Pt.) Anais da lations of larvae of Busseola fusca (Fuller) in northern Sociedade Entomologica do Brasil 13:3-94. Nigeria. Bulletin of Entomological Research 54:643-647. Campion, D . G . , and Nesbitt, B.F. 1983. The utilisation of Harris, K . M . 1985. Lepidopterous stem borers of s o r g h u m . sex pheromones f o r the c o n t r o l of stem-borers. Insect Pages 161-167 in Proceedings of the I n t e r n a t i o n a l Science and its Application 4(1-2):191-197. Sorghum Entomology Workshop, 15-21 Jul, 1984, College Chadha, G.K.,and Roome, R.E. 1980.Ovipositionbehav- Station, Texas, USA. Patancheru, A.P. 502 324, India: i o u r and the sensilla of the o v i p o s i t o r of Chilopartellus and International Crops Research Institute for the Semi-A r i d Spodoptera littoralis (Lepidoptera: Noctuidae). Journal of T r o p i c s . Z o o l o g y 192:169-178. Holloway, T.E., Haley, W.E., and Loftin, U.C. 1928. T h e Chapman, R . F . , a n d Woodhead, S. 1985. Insect behavior sugarcane moth borer in the United States. Technical B u l - in s o r g h u m resistance mechanisms. Pages 137-147 in P r o - letin no.4I. Washington, D.C., USA: United States ceedings o f the International S o r g h u m E n t o m o l o g y W o r k - Department of Agriculture. 76 pp. shop, 15-21 J u l 1984, College S t a t i o n , Texas, U S A . Ingram, W . R . 1958. T h e lepidopterous stalk borers asso- Patancheru. A.P. 502 324, India: International Crops ciated with Gramineae in Uganda. Bulletin of Entomologi - Research Institute for the S e m i - A r i d T r o p i c s . cal Research 49:367 383. Chapman, R.F., Woodhead, S., and Bernays, E.A. 1983. Ingram, W . R . 1983. Biological control of graminaceous Survival and dispersal of y o u n g larvae of Chilo partellus stem-borers and legume pod-borers. Insect Science and its (Swinhoe) ( L e p i d o p t r a : Pyralidae) in t w o cultivars of Application 4(1-2):205-209. sorghum. Bulletin of Entomological Research 73:65-74. Jepson, W . R . 1954. A critical review of the world literature du Plessis, C.,and Lea, H . A . F . 1943. T h e maize stalk borer on the lepidopterous stalk-borers of tropical graminaceous Calamistis fusca (Hmpsn.). Bulletin of the Department of crops. London, UK: Commonwealth Institute of Entomol- Agriculture and Forestry, Union of South Africa no.238. ogy. 127 pp. 51pp. K a u f m a n n , T. 1983. Observations on the host plant adap- Fuchs,T.W.,and Harding, J.A. 1979. Seasonal abundance tations of Busseola fusca ( L e p i d o p t e r a : Noctuidae) in of the sugarcane borer, Diatraea saccharalis, on sugarcane Nigeria. Proceedings of the E n t o m o l o g i c a l Society of and other hosts in the L o w e r R i o Grande Valley of Texas. Washington 85:321-326. Southwestern Entomologist 4:125-131. M a l l y , C . W . 1920. The maize stalk borer, Busseola fusca, Fuchs, T.W., Harding, J.A., and Smith, J.W. 1979. Induc- Fuller. Bulletin of the Department of Agriculture, Un i o n of t i o n and t e r m i n a t i o n of diapause in the sugrcane borer. South Africa no.3. 111pp. A n n a l s of the E n t o m o l o g i c a l Society of A m e r i c a 72:271- 274. Mendes, A . C . 1978. Influence of climatic factors on the populations of the sugarcane m o t h borer, Diatraea saccha- Gahukar, R . T . 1984. Senegal new insect pests of s o r g h u m . ralis (Fabr.), and root froghopper, Mahanarva fimhriolate F A O Plant Protection Bulletin 32:31-33. (Stal.) Sao Paulo, Brazil. Entomology, Newsletter 13. Girling, D . J . 1978. The d i s t r i b u t i o n and biology of Eldana Mendes, A.C., Botelho, P.S., and Macedo, N. 1978. A l t u r a saccharina Walker (Lepidoptera: Pyralidae) and its rela- de v o o , hora de voo e influencia das fases lunares sobre a t i o n s h i p to other stem-borers in Uganda. Bulletin of E n t o - captura de adultos da Diatraea saccharalis ( F a b r . , 1794) m o l o g i c a l Research 68:471-488. atrave de armadilhas luminosas. (In Pt.) Brasil Acucareiro Girling, D . J . 1980. Eldana saccharina as a crop pest in 92:21-33. G h a n a . T r o p i c a l Pest Management 26:152-156. Mohyuddin, A.I., Inayatullah, C., and King, E.G. 1981. G o u l d , F . W . , a n d Shaw, R.B. 1983. Grass systematics. 2nd Host selection and strain occurrence in Apanteles flavipes edn. College S t a t i o n , Texas, U S A : Texas A & M University (Cameron) (Hymenoptera: Braconidae) and its bearing on Press. 397 pp. biological control of graminaceous stem-borers (Lepid o p - tera: Pyralidae). Bulletin of Entomological Research H a l l , D.R., Beevor, P.S., Cork, A., Lester, R., Nesbitt, 71:575-581. B.F., Nyirenda, G.K.C., Nota Phiri, D.D., Blair, B.W.,and Tannock, J. 1981. T h e female sex pheromone of the maize Nesbitt, B.F., Beevor, P.S., Hall, D.R., Lester, R., Davies, stalk-borer, Busseola fusca (Fuller) (Lepidoptera: Noctui- J . C . , and Seshu Reddy, K.V. 1979. C o m p o n e n t s of the dae): identification and initial field trials. Zimbabw e . Z i m - female sex pheromone of the spotted stalk-borer, Chilo babwe Journal of Agricultural Research 19:111-122. partellus (Swinhoe) (Lepidoptera: Pyralidae): identification and preliminary field trials. Journal of Chemica l E c o l - H a m m o n d , A . M . and Hemsley, S . D . 1971. The sugarcane ogy 5:153-16. borer sex attractant. Entomophaga 16:159-164.

70 Nesbitt, B.F., Beevor, P.S., Cork, A . , H a l l , D . R . , Lester, Usua, E.J. 1970. Diapause in the maize stemborer. Journal R., Blair, B.W., and Tannock, J. 1980. Identification of the o f Economic E n t o m o l o g y 63:1605-1610. female sex p h e r o m o n e of the maize stalk-borer, Busseola Usua, E.J. 1974. Observations on the physiology of dia- fusca : a preliminary note. Tropical Pest Management pause and non-diapause larvae of Busseola fusca (Fuller) 26(3):327. (Lep.: Noctuidae). Bulletin of Entomological Research Neupane, F.P., Coppel, H.C., and Chapman, R.K. 1985. 63:513-518. B i o n o m i c s of the maize borer, Chilo partellus S w i n h o e , in van Rensberg, J.B.J. 1980. Selective oviposition by the Nepal. Insect Science and its A p p l i c a t i o n 6:547-553. maize stalk borer, Busseola fusca (Fuller). Proceedings of Nwanze, K . F . 1985. S o r g h u m insect pests in West A f r i c a . the Congress of the Entomological Society of Southern Pages 37-43 in Proceedings of the International Sorghum Africa 3:23-24. Entomology Workshop, 15-21 Jul 1984, College Station, van Rensberg, J.B.J., Walters, M.C., and Giliomee, J.H . Texas, U S A . Patancheru, A . P . 502 324, I n d i a : Interna- 1987. Ecology of the maize stalk borer, Busseolla fusca tional Crops Research Institute for the Semi-Arid Tropi c s . (Fuller) (Lepidoptera: Noctuidae). Bulletin of Entomolo g i - Riek, E.K. 1970. Pages 168-186 in T h e insects of Australia: cal Research 77:255-269. a text-book for students and research workers, (CSIRO, Young, W.R. 1970. S o r g h u m insects. Pages 235-237 in Canberra, corporate authorship). Melbourne University Sorghum production and utilization (Wall, J.S., and Ross, Press, x i i i + 1029 pp. W.M., eds.). Westport, Connecticut, USA: AVI Publish- Roe, R . M . , H a m m o n d , A . M . , Reagan, T . E . , and Hensley, ing C o . S . D . 1981. A b i b l i o g r a p h y of the sugarcane borer, Diatraea Young, W.R., and Teetes, G.L. 1977. S o r g h u m e n t o m o l - saccharalis (Fabricius), 1987-1980. Agricultural Reviews ogy. A n n u a l Review of E n t o m o l o g y 22:193-218. and M a n u a l s , A R M - S - 2 0 . W a s h i n g t o n , D.C., U S A : U n i - ted States D e p a r t m e n t of A g r i c u l t u r e .

Sampson, M . A . , and Kumar, R. 1985. Life history, development and behaviour of Eldana saccharina W a l k e r on sugar-cane in southern G h a n a . Insect Science and its Application 6:135-143.

Seshu Reddy, K.V. 1985. Integrated approach to the con- t r o l of s o r g h u m stem borers. Pages 205 -215 in Proceedings o f the I n t e r n a t i o n a l S o r g h u m E n t o m o l o g y W o r k s h o p , 15-21 J u l 1984, College S t a t i o n , Texas, U S A . Patancheru, A . P . 502 324, India: I n t e r n a t i o n a l Crops Research Insti- tute f o r the S e m i - A r i d Tropics.

Singh, B . U . , and R a n a , B.S. 1984. Influence of varietal resistance on o v i p o s i t i o n and larval development of stalkborer Chilo partellus S w i n . , and its relationship to field resistance in sorghum. Insect Science and its Applicati o n 5:287-296.

Smithers, C . N . 1960a. Some recent observations on Bus- seola fusca ( F u l l e r ) (Lep., Noctuidae) in southern R h o d e - sia. Bulletin of Entomological Research 50:809-819.

Smithers, C . N . 1960b. Moisture and pupation in Busseola f u s c a (Hmps.) (Lepid.: Noctuidae). Journal of the Entomo- logical Society of S o u t h e r n A f r i c a 23:225-227.

Swaine, G. 1957. T h e maize and s o r g h u m stalkborer, Bus- seola fusca (Fuller), in peasant agriculture in Tanganyika Territory. Bulletin of Entomological Research 48:711-722.

Teran, F.O. 1979. Dinamica populacional de adultos de Diatraea saccharalis (Fabricius, 1979) em canaviais do Estado de Sao Paulo. Anais de Sociedade E n t o m o l o g i c a do Brasil 8:3-17.

Teran, F.O. 1983. Densidade larval de Diatraea saccharalis (Fabricius, 1794) e seu controle n a t u r a l em m i l h o . ( I n Pt.) Anais da Sociedade Entomologica do Brasil 12:1-40.

7 1

Chemical Control of Stem Borers

Prem Kishore1

Abstract

Chemical control is the most powerful tool available for controlling stem borers and is an important component in their management. The most important borer species on sorghum and maize are Chilo partellus, Busseola fusca, Sesamia spp, Eldana saccharina, and Diatraea spp. The knowledge of specific habits and periods of peak activity of the most vulnerable stages of stem borers with appropriate formulation, method, rate, time, and schedule of application of insecticides determine the degree of success of chemical control. This paper reviews recent research and recommendations on chemical control of major stem borers, and also discusses judicious use of endosulfan and its integration with host-plant resistance.

Introduction 1960, and Kayumbo 1976). Chemical control of stem borers in South A f r i c a has been reported tobe inef• Chemical c o n t r o l , despite its limitations, is an fective (van Rensburg and van H a m b u r g 1975). i m p o r t a n t t o o l for consideration in any integrated Besides C. partellus, attention has been given to use pest management program, especially in treating of insecticides for the control of rice stem borers, epidemics. It requires application methods based on B. fusca and Maruca testulalis. Little i n f o r m a t i o n is specific insect habits, peak period of activity, and available on the chemical control of other cereal vulnerable stages of the life cycle. Economic thresh• stem borers. olds are also i m p o r t a n t considerations of chemical c o n t r o l , both for effective application and for m i n • i m u m impact on environment (avoiding destruction Soil Furrow Application at Sowing of natural enemies of pests by toxic residues). M o s t w o r k on chemical c o n t r o l of stem borers in Chemical control of C. partellus t h r o u g h soil f u r r o w India has been done on C. partellus, while very little application at sowing of systemic insecticides such as has been done in East A f r i c a (Coaker 1956, Nye cytrolane 5G, carbofuran 5-10G, aldicarb 10G,

1. Entomologist, Division of Entomology, Indian Agricultural Research Institute (IARI), New Delhi 110 012, India.

I C R I S A T (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, l C R I S A T Center. India. Patancheru, A.P. 502 324, India: ICRISAT.

73 mephosfolan 10G, phorate 10G, and disulfoton of S. calamistis, B. fusca, E. saccharina, S. cretica, 10G, at 0.7-2.0 kg a.i. ha-1 has been tried w i t h suc- Ostrinia nubilalis, and C. agamemnon on maize in cess (Grewal 1969, Baskaran 1971, N o o r and Pareek Nigeria ( A d e y m i et al. 1966, and Saad et al. 1971). 1978, and Chatterji et al. 1972). Sharma et al.(1973) Chlorpyrifos and c h l o r d i m i f o r m as u l t r a l o w volume reported no differences between application of vir- sprays (ULV), and diazinon, chlorpyrifos, mephos- lane, cytrolane, phorate, or carbofuran and control. folan and EPN as conventional sprays, were effec- Walters and Drinkwater (1975) reported significant tive against 5. cretica in Baghdad (Saad 1977). Spray reduction of B. fusca by carbofuran granules at 1 kg application of chlorfenvinphos, diazinon, and azi- - 1 a.i. ha-1). Similar findings were made by van Rens- nophos methyl at 0.2-0.6 kg a.i. ha were effective in burg et al.(1978). rice against Chilo spp., M. separatella, Tryporyza spp., and Sesamia spp. A p p l i c a t i o n of malathion 50 EC at 1.5 kg a.i. h a -1, or Basudin 60 EC at 1.2 kg a.i. S e e d T r e a t m e n t ha- 1 were f o u n d effective in controlling B. fusca, Sesamia spp., Chilo spp., and M. separatella (Sagma Lal et al. (1961) tried finely g r o u n d B H C and lindane 1983). A chlorpyrifos seedling root dip treatment, as seed treatment f o r C. partellus c o n t r o l on maize. followed by foliar spray applications of 0.5 kg a.i. - 1 G u m arabic paste was used as a sticker. B H C ha at 25 and 60 D A E , effectively controlled the ( 5 g / 100g) and lindane (20g/ 100g) of seeds gave p r o - Scirpophaga incertulas. Application of mephosfo- -1 tection against C. partellus. Higher concentrations lan to the r o o t zone at 0.5 kg a.i. h a , plus spray were phytotoxic. Sharma et al. (1973) also tried seed application four days after treatment, also effec- treatment w i t h carbofuran at 5.75-10 g a.i. /100 g tively controlled the pest (Sasmal et al. 1984). Foliar seed w i t h little success. spray of fenobucarb, cartab, and fenvalerate reduced the incidence of stem borer Scirpophaga innotata to a greater extent than the other insecticides (Utham- S i d e - d r e s s i n g A f t e r C r o p E m e r g e n c e asamy and Jayraj 1985).

Jotwani (1969) determined the feasibility of controlling sorghum stem borers by side-dressing w i t h Leaf Whorl Placement of Insecticides mephosfolan and c a r b o f u r a n , 20 days after emergence ( D A E ) . Other efforts f o u n d that mephosfolan, Placement of insecticide directly into the w h o r l of aldicarb, and carbofuran granules applied 15-34 maize and sorghum plants solves the problem of D A E at 1.0-2.5 kg a.i. ha- 1 gave effective protection keeping the chemical on the leaves at lower applica- against C. partellus on maize and sorghum (Grewal t i o n rates per unit area. 1969, Chatterji et al. 1972, and S h a r m a et al. 1973).

F o l i a r S p r a y s a n d D u s t s Application of Granules

F o l i a r sprays and dusts o f D D T , B H C , and para- In early trials, endrin granules in leaf whorls gave t h i o n were used on local varieties of sorghum and effective c o n t r o l of C. partellus (Thobbi et al. 1968, maize to c o n t r o l stem borers (Trehan and Butani Kulshrestha et al. 1968, and A h m e d and Y o u n g 1949, Puttarudriah 1958). Later insecticides such as 1969). Also reported to be effective against this pest endrin, carbaryl, monocrotophos, diazinon, fenitro- were endosulfan, carbaryl, phenthoate, quinalphos, t h i o n , and phenthoate were evaluated for use against malathion, lindane, mephosfolan, and diazinon gra- C. partellus in I n d i a ( Y o u n g 1962, and A h m e d and nules at 0.600-1.200 kg a.i. ha- 1 ( J o t w a n i and Y o u n g Y o u n g 1969). Spray applications of the pyrethroids 1972, Jotwani and Kishore 1973, Noor and Pareek decamethrin, fenvalerate, cyloxylate, cypermethrin, 1978, Taley and Thakare 1979, Sandhu and Chahal and permethrin at 25-150 g a.i. ha-1, were not very 1980, and K u n d u and Kishore 1980). effective against this pest (AICSIP 1982-83). Helicopter application of monocrotophos 2G and E n d r i n spray at weekly intervals was effective endrin 3G at 20 kg ha- 1 reduced larval population of against D. crambidoides (Brett 1953, and George Sesamia spp. on maize in Spain (Caballero et al. and W i l s o n 1957). T w o applications of carbaryl and 1972). Single applications of carbofuran, diazinon, cytrolane, either spray or dust, reduced the damage or chlorfenvinphos granules were also f o u n d to be

7 4 effective against S. cretica in maize ( A l - D a b b a s and spray of carbaryl mettable powder ( W P ) in the leaf A l - S a l i h 1978). whorls of each plant using a specially designed pistol Recommendations for the control of rice stem grip sprayer. borers, C h i l o s p p , Sesamia spp., M. separatella, and T. incertuJus include granular application of B H C , carbofuran, chlordimeform, chlorfeminphos, dia- Comparison of Application Methods zinon, fensulfothion, mephosfolam, or salithion at - 1 0.45-2 kg a.i. ha (COPR 1976, pp. 122-123). Different application methods using endosulfan, phenthoate, and carbaryl against C. partellus, in sorghum showed that granules and dusts were super- Application of Dusts ior to sprays in realizing grain and fodder yields. N ot much difference was observed between granules and Kishore and J o t w a n i (1977) f o u n d leaf w h o r l place- dusts (Table 1, Kishore 1980). J o t w a n i and Y o u n g ment of dusts of endosulfan, phenothoate, carbaryl, (1972) demonstrated the superiority of granules over m a l a t h i o n , and B H C to be economically feasible in sprays. Endosulfan spray and granules together controlling stem borers in sorghum. These findings have been found effective against this pest in maize were subsequently proved effective at different loca- ( M a t h u r 1983). tions (AICSIP 1977-79). Results of trials conducted in 1986-87 at I A R I , D e l h i , showed that dust of fenvalerate applied in leaf whorls is also effective Economic Threshold against this pest. Swaine (1957) controlled B. fusca w i t h 2.5% D D T Repeated applications of BHC, DDT, parathion dust applied at weekly intervals on maize. Walker and endrin have been tested for their ability to con- (1960) reported effectiveness of endrin dust in control sorghum stem borers. No significant difference t r o l l i n g B. fusca on maize, van Rensburg and H a m - was f o u n d between 3 and 6 applications of endrin b u r g (1975) c o u l d not get effective c o n t r o l of (Thobbi et al. 1968). Various insecticide application C. partellus in South Africa. schedules have also been tested. (Ingram 1958, Jot- wani and Young 1972, M a n o h a r a n and Balasubra- manian 1982, and Sachan and Rathore 1983). H o w - Application of Sprays ever, in the absence of economic thresholds for Barry and Andrews (1971) obtained satisfactory various stem borers it is d o u b t f u l that insecticide c o n t r o l of B. fusca in sorghum by applying a 1 mL application is justified by infestation levels.

Table 1. Efficacy of different formulations of promising insecticides for the control of stem borer.

Increase Borer damage in grain A v o i d a b l e Yield t ha-1 (mean) M e a n leaf M e a n stem yield over loss Insecticide i n j u r y (%) tunneling (%) G r a i n Fodder control (%) (grain) (%)

Endosulfan granules 18.90 17.35 0.57 2.66 83.98 0.00 Endosulfan dust 19.16 16.21 0.57 2.40 83.85 0.10 Endosulfan spray 32.51 41.44 0.37 2.15 19.43 35.08 Phenthoate granules 19.78 17.94 0.56 2.52 81.14 1.54 Phenthoate dust 20.23 18.40 0.56 2.27 80.27 2.01 Phenthoate spray 31.63 40.58 0.36 2.09 15.94 36.98 C a r b a r y l granules 20.09 18.63 0.56 2.48 80.60 1.84 C a r b a r y l dust 20.33 19.45 0.55 2.26 78.34 4.82 C a r b a r y l spray 32.07 41.09 0.36 2.17 16.59 36.63 C o n t r o l ( N o treatment) 48.30 43.97 0.31 1.76 0.00 47.40

SE ±0.026 ±0.0045 ±0.0085 ±0.15

C D at 5% 0.076 0.031 0.025 0.43

S o u r c e : K i s h o r e 1 9 8 0 .

75 Based on economic threshold studies in maize, the Chemical Control and Integrated most vulnerable period of borer damage was f o u n d C o n t r o l to be 10-17 D A E and the insecticide application should be initiated between 10 and 12 D A E (Sarup et al. 1977). Quantities of insecticides can be reduced to an eco- Kishore (1984b), w o r k i n g on t i m i n g and schedule nomic level by integrating their use with resistant of insecticide application in sorghum, f o u n d that varieties and cultural practices (Kishore and Jot- two applications of endosulfan 4% dust at 5.0 and wani 1982). Studies show that endosulfan applica- 7.5 kg ha-1, given on 25 and 35 D A E were as effective t i o n can be integrated w i t h 12 stem-borer resistant as. and more economical t h a n , applications given on varieties to achieve marginal benefits under moder- 20. 30,40 D A E in c o n t r o l l i n g stem borer. W i t h this ate levels of infestation (Table 3) (Kishore and G o v i l schedule, the rate of application of endosulfan was 1982, and Kishore 1984a). reduced to 12.5 kg ha- 1 f r o m 22.5 kg ha- 1 (Table 2).

D i s c u s s i o n a n d C o n c l u s i o n s Persistence a n d R e s i d u e s Stem borers of maize and sorghum can be effectively N o t m u c h w o r k has been done on the persistence controlled by leaf whorl placement of granular or and residues of insecticides tried against different dust applications of endosulfan, phenthoate, qui- stem borers. Concern over endrin residues in sor- nalphos, carbaryl, malathion, and fenvalerate. This g h u m contributed to the ban of its use. Studies con- application targets the vulnerable stage of the pests ducted on persistence and residues of carbofuran, as the larvae move towards leaf whorls after hatch- chlorfenvinphos, chlorpyrifos, lindane, endosulfan, ing. The insecticide is less affected by rain and its fensulfothin, quinalphos, monocrotophos and tetra- quantity can be reduced t h r o u g h this application chlorvinphos indicate that, in most cases, significant method. Hazards of pollution residues and effects reduction in residues was observed 45 days after on non-target organisms can also be avoided. application. At harvest, none of the insecticides Determining economic thresholds for different showed detectable residues in grain, except carbofu- stem borers is desirable both to realize m a x i m u m r a n . T h e residues of c a r b o f u r a n were below the t o l - benefit of chemical controls and to reduce the erance l i m i t (Srivastava 1975, M a n o h a r a n and Bala- number of applications. Efforts should be made to subramanian 1982, and G u r u r a j 1986). avoid highly toxic and persistent insecticides and to

Table 2. Efficacy of different insecticidal schedules in the control of stem borer of sorghum.

Endosulfan 4 % Increase in grain yield Mean grain yield (t ha-1) dust applied over control (t ha-1) Cost-benefit (days after g e r m i n a t i o n ) Year l Year I I ( M e a n 2 years) r a t i o

20 at the rate 5 kg ha-1 0.41 0.41 0.13 1:34.14 25 at the rate 5 kg ha-1 0.42 0.43 0.14 1:37.45 20 and 30 at the rate of 5 a n d 7.5 kg ha-1 0.41 0.42 0.13 1:14.39 30 at the rate of 7.5 kg h a - 1 0.35 0.36 0.07 1:13.76 35 at the rate of 7.5 kg ha-1 0.35 0.34 0.06 1:11.27 20, 30, a n d 40 at the rate of 5, 7.5, and 10 k g ha-1 0.45 0.46 0.18 1:10.87 25 a n d 35 at the rate of 5 a n d 7.5 kg ha- 1 0.47 0.49 0.20 1:22.25 40 at the rate of 10 kg ha- 1 0.32 0.34 0.04 1: 6.06 C o n t r o l ( N o treatment) 0.28 0.29 - -

SE ±0.021 ±0.01

C D at 5 % 0.063 0.04

S o u r c e : K i s h o r e 1984b.

7 6 Table 3. Stem borer damage and grain yield of selected resistant varieties of sorghum with and without the application of insecticide.

Stem t u n n e l i n g by the stem borer (%) G r a i n yield (t ha-1)

Year I Year I I Year l Year I I Increase in g r a i n yield (%) N o n p r o - P r o - N o n p r o - P r o - N o n p r o - P r o - N o n p r o - P r o - E n t r y tected tected tected tected tected tected tected tected Year l Year I I

E 601 11.85 9.32 14.10 12.51 0.46 0.48 0.47 0.50 6.88 4.62 E 602 13.20 10.62 15.35 13.44 0.44 0.46 0.47 0.49 7.19 4.54 E 603 13.92 11.19 15.70 14.26 0.43 0.46 0.46 0.48 6.46 3.13 E 6 0 4 16.47 13.71 16.74 15.13 0.42 0.44 0.45 0.46 5.64 2.15 E 605 19.53 16.55 17.48 16.28 0.41 0.44 0.44 0.45 6.60 2.64 E 606 17.46 16.51 16.39 13.05 0.41 0.43 0.44 0.45 3.61 2.97 E 607 19.48 13.38 17.48 13.93 0.41 0.42 0.45 0.46 3.30 2.09 E 608 21.97 19.76 18.73 14.88 0.40 0.42 0.43 0.45 4.50 3.07 E 609 23.02 15.98 22.11 20.31 0.40 0.43 0.43 0.44 8.09 2.67 E 610 22.12 19.33 22.22 21.15 0.40 0.42 0.39 0.43 5.06 8.99 E 6 1 1 23.63 19.75 20.31 18.23 0.38 0.42 0.40 0.42 9.14 4.79 E 612 23.58 21.41 20.46 17.95 0.39 0.42 0.39 0.43 7.05 10.67 C S H 1 45.40 29.47 41.55 28.43 0.27 0.40 0.29 0.41 48.33 40.72

M e a n 20.89 16.69 19.89 16.87 0.43 0.40 0.42 0.45

SE ±0.012 ±0.0072 ±0.01 ±0.022

C D at 5 % 0.035 0.020 0.03 0.065

S o u r c e : K i s h o r e 1984a.

generate data on residues. Integration of chemicals Ayoade, K.A. 1969. Insecticidal c o n t r o l of the pod-borer w i t h other methods of control is possible. Maruca testulalis Gey. (Lepidoptera: Pyralidae) on west bred cowpea (Vigna sp.). Bulletin of the Entomologica l Society of Nigeria 5:23-S33.

Al-Dabbas, A.K.,and Al-Salih, G.A. 1978. Chemical c o n - R e f e r e n c e s trol of corn stem-borer, Sesamia cretica Led. ( L e p i d o p t e r a - Phalaenidae) and d e t e r m i n a t i o n of times of insecticide application. Pages 79-81 in Year b o o k of Plant Protection Adeymi, S.A.O., Donnelly, J., and Odetoyinbo, J.A. 1966. Research, 1974/1976,1. Baghdad, Iraq: Ministry of Agri - Studies on chemical c o n t r o l of the stem-borers of maize. culture and A g r a r i a n R e f o r m . N i g e r i a n A g r i c u l t u r a l J o u r n a l 3:61-66. Barry, B.D., and Andrews, D. 1971. A sprayer f o r the A h m e d , S . M . , a n d Young, W . R . 1969. Field studies on the c o n t r o l of Busseola fusca in the whorls of s o r g h u m . J o u r - chemical c o n t r o l of stem-borers, C. partellus on h y b r i d nal of Economic Entomology 67:310-311. s o r g h u m i n I n d i a . J o u r n a l o f E c o n o m i c E n t o m o l o g y 62:478-482. Baskaran, P. 1971. Efficacy of soil applied insecticides for the c o n t r o l of s o r g h u m shootfly and stem-borer. P h . D . A I C S I P ( A l l India Coordinated Sorghum Improvement thesis, Indian Agricultural Research Institute, New De l h i , Project) 1977-79. Progress reports of the A l l India C o o r d i - I n d i a . nated Sorghum Improvement Project, Entomology Sec- t i o n , I n d i a n C o u n c i l o f A g r i c u l t u r a l Research a n d Brett, C.H. 1953. Southern cornstalk borer w i t h m e t h o - Cooperating Agencies. New Delhi, India: AICSIP. dychlor, DDT, isodrin and endrin. Journal of Economic Entomology 46(1): 176. A I C S I P ( A l l India Coordinated Sorghum Improvement Project) 1982-83. Progress reports of the All India Coordi- Caballero, G., de Vinuesa, J.I., Alvarado Cordobes, M., nated Sorghum Improvement Project Entomology Sec- and Bernaldel Villaj, J.M. 1972. C o m p a r a t i v e test of the t i o n , I n d i a n C o u n c i l o f A g r i c u l t u r a l Research and effectiveness of a z o d r i n and e n d r i n against the maize borer Cooperating Agencies. New Delhi, India: AICSIP. 1971. Boletin I n f o r m a t i v e de Plagas 90:31-36.

77 Charterji, S . M . , S a r u p , P., Bnamburkar, M . W . , M a r w a h a , Kishore, P. 1984a. Integration of host plant resistance and K.K., Panwar, V . P . S . , and Siddiqui, K . H . 1972. E v o l u t i o n chemical control for the management of sorghum stem of c o n t r o l schedule f o r the pests of maize w i t h particular borer. Indian Journal of Agricultural Sciences reference to stem borer, Chiio zonellus (Swinhoe). I n d i a n 54(2):131-133. Journal of Entomology 34:142-147. Kishore, P. 1984b. Timing and schedule of application of Coaker, T . H . 1956. A n experiment o n maize stalk borer endosulfan to c o n t r o l s o r g h u m stem borer. I n d i a n J o u r n a l control on maize. East African Agricultural Journal of Agricultural Sciences 54(5):415-417. 21:220-221. Kulshrestha, J.P., Rao, S.B.P., and Singh, V.S. 1968. A C O P R (Centre for Overseas Pest Research) 1976. Pest comparative study of different granular forms of insecti- c o n t r o l i n rice. P A N S M a n u a l no. 3 . L o n d o n , U K : C O P R . cides against sorghum. Sorghum Newsletter 11:25-27.

George, E.C.,and Wilson, M . C . 1957. Granulated insecti- Kundu, G . G . , and Kishore, P. 1980. Chemical c o n t r o l of cides f o r European c o r n borer c o n t r o l . J o u r n a l of Eco- s o r g h u m stem borer, Chilo partellus (Swinhoe). Indian nomic E n t o m o l o g y 50 (2):251-257. Journal of Entomology 42(4):791 -793.

Grewal, S.S. 1969. Farmers: beware of maize borer. Pro- Lal, R., R a i , B.K., and Kanta, S. 1961. Preliminary investi- gressive F a r m i n g 5(8):4-5. gation on seed treatment for the protection of young maize plants f r o m insect infestation. I n d i a n J o u r n a l o f E n t o m o l - Gururaj, K. 1986. Studies on persistance of endosulfan and ogy 23(2):155-157. quinalphos on s o r g h u m c r o p . P h . D . thesis, I n d i a n A g r i c u l - t u r a l Research Institute, N e w D e l h i , I n d i a . M a n o h a r a n , T., and Balasubramanian, M. 1982. Effect of lindane in controlling the sorghum stem borer, Chilo p a r - Ingram, W . R . 1958. T h e lepidopterous stalk borers asso- tellus (Swinhoe) and their persistance in sorghum. Madras ciated w i t h G r a m i n e a l i n Uganda. Bulletin o f E n t o m o l o g - Agricultural Journal 69(1):33-38. ical Research 49:367-387. M a t h u r , L . M . L . 1983. Research findings in maize ento- Jotwani, M . G . 1969. N e w trends in the c o n t r o l of s o r g h u m mology. Udaipur, Rajasthan, India: Sukhadia University. pests. W o r l d Science News 4(4):8-12. Noor A . , and Pareek, B.L. 1978. Relative effect of some Jotwani, M . G . , and Kishore, P. 1973. C o n t r o l of stem insecticidal treatments on control of maize stem borer. borer, Chilo partellus (Swinhoe) on high yielding sorghum E n t o m o n 3:193-196. hybrids C S H - 1 and C S H - 3 . Entomologists' Newsletter 3(8);51-52. Nye, I . W . B . 1960. The insect pests of graminaceous crops in East Africa. Colonial Research Study no 31. London, Jotwani, M . G . , and Young, W . R . 1972. Recent develop- U K : Her Majesty's Stationery Office. 48 pp. ments in chemical c o n t r o l of insect pests of s o r g h u m . Pages 377-398 in s o r g h u m in seventies ( R a o , N . G . P., and House, Puttarudriah, M. 1958. Glimpses of agricultural entomol- L.R., eds.). N e w D e l h i , India: O x f o r d and I B H Publishing ogy in Mysore. Dharwar Agriculture College Magazine C o . 11:8-39.

Kayumbo, H . Y . 1976. Incidence of the spotted borer Chilo Saad, A.S.A.K. 1977. Aerial spraying for the control of sp. on s o r g h u m in M o r o g o r o region, Tanzania. Presented Sesamia cretica Led. on corn in Iraq. Mededelingen van de at the S i x t h East A f r i c a n Cereals Research Conference, Faculteit Land bouwwetenschappen Rijksuniversiteit Gent 13-18 M a y 1976, M o r o g o r o , Tanzania. 42:911-913.

Kishore, P., and Jotwani, M . G . 1977. Efficacy of leaf whorl Saad, A . S . A . K . , Zeid, M . , and El-Sebae, A . H . 1971. placement of insecticidal dust against Chilo partellus Chemical control of Sesamia cretica Led. Chilo agamem- (Swinhoe). Entomologists' Newsletter 7(6):30. non Bles. and Ostrinia nubilalis Hb. (Lepidoptera) and Kishore, P. 1980. Integrated approach for the control of number of sprays required. Zeitschrift fuer A n g e w a n d t e Chilo partellus (Swinhoe), a serious pest of s o r g h u m . Entomologie 69:91-98. Ph.D. thesis, Indian Agricultural Research Institute, N e w Sachan, G.C., and Rathore, Y . C . 1983. Studies on the D e l h i , I n d i a . complete protection of s o r g h u m c r o p against insect pests Kishore, P., and Govil, J . N . 1982. U t i l i z a t i o n of host plant by chemicals at various stages of c r o p g r o w t h . Pesticides resistance f o r j u d i c i o u s use of insecticides in s o r g h u m . 17(6):15-16. A g r i c u l t u r e Science Digest 2(2):101-104. Sagina, S.B. 1983. Possible integrated pest management Kishore, P., and Jotwani, M . G . 1982. Integrated pest man- tools for the effective control of cereal stem borers in the agement in Sorghum. Journal of Environmental Research Gambia. Insect Science and its Application 3(1):1-7. 4(1-2):217-219.

78 Sandhu, G.S., and Chahal, N.S. 1980. Comparison of Walker, P.T. 1960. Insecticide studies on maize stalk borer, different chemical methods for the c o n t r o l of C. partellus Busseola fusca in East Africa. Bulletin of Entomological on maize. I n d i a n J o u r n a l of E n t o m o l o g y 43(4):408-413. Research 51(2):321-351.

Sarup, P., Sharma, V . K . , and Panwar, V . P . S . , Siddiqui, Walters, M . C , and Drinkwater, T . W . 1975. Preliminary K . H . , M a r w a h a , K . K . , a n d Agarwal, K . N . 1977. E c o n o m i c studies on the application of systemic insecticides to the soil threshold of Chilo partellus (Swinhoe) infesting maize. f o r the c o n t r o l of maize stalk borer, Busseola fusca (Fuller) Journal of Entomological Research 1(1):92-99. (Lep.: Noctuidae). Phytophylactica 7:121-124.

Sasmal, S., Kulshrestha, J.P., and Rajamani, S. 1984. Young, W . R . 1962. Insect c o n t r o l studies. S o r g h u m New- Chlorpyriphos spraying is economical in controlling stem sletter 5:63-64. borer in rabi rice. Rice Research Newsletter 4(3-4):3.

Sharma, V . K . , Singh, J . M . , and Chaudhary, R . N . 1973. Chemical c o n t r o l of maize stem borer Chilo partellus (Swinhoe). Pages 222-223 in A n n u a l report 1972 73. Pant- nagar, U t t a r Pradesh, India: G.B. Pant University of A g r i - culture and Technology.

Srivastava, K.P. 1975. Chemical control of sorghum pests and studies on persistance of insecticides used on s o r g h u m crop. Ph.D. thesis, Indian Agricultural Research Institute, New D e l h i , India.

Swaine, G. 1957. The maize and s o r g h u m stalk borer Bus- seola fusca (Fuller), in peasant agriculture in Tanganyika territory. Bulletin of Entomological Research 48:711-722.

Taley, Y . M . , a n d Thakare, K.R. 1979. Chemical control of s o r g h u m tissue borers. I n d i a n J o u r n a l of Entomology 41:134-138.

Thobbi, V . V . , Vedamoorthy, G., Jotwani, M . G . , Kulshres- tha, J.P., Katiyar, R . N . , and Young, W . R . 1968. Insect c o n t r o l studies on the new h y b r i d s o r g h u m C S H - 1 in I n d i a . Indian J o u r n a l o f E n t o m o l o g y 30(1):48-50.

Trehan, K . N . , and Butani, D . K . 1949. Note on life history, bionomics and c o n t r o l of Chilo zonellus (Swinhoe) in Bombay Province. Indian Journal of Entomology 11:47-59.

Uthamasamy, S., and Jayaraj, S. 1985. Efficacy of certain newer insecticides in the c o n t r o l of m a j o r pests of rice. Pesticides 19(9):37-46. van Rensburg, N.J. and van H a m b u r g , H. 1975. G r a i n s o r g h u m pests. An integrated c o n t r o l a p p r o a c h . Pages 151 162 in Proceedings of 1st Congress Engomological Society of S o u t h A f r i c a . van Rensburg, J.B.J., and Walters, M . C . 1978. The efficacy of systemic insecticides applied to the soil f o r the c o n t r o l of Cicadulina mbila (Naude) ( H e m . Cicadelidae) the vector of maize streak disease, and the maize stalk borer Busseola fusca (Fuller) (Lep: Noctuidae). Phytophylactica 10:49-52. van Rensburg, J.B.J., Walters, M.C, and Stemmet, G.P. 1978. A preliminary study on the application of carbofuran granules to the soil f o r the c o n t r o l of grain s o r g h u m pests. Phytophylactica 10:28-30.

Cultural Control of Sorghum Stem Borers

A . N . Verma1 and S.P. Singh2

Abstract

The role of cultural practices such as time of sowing, crop rotation, tillage, plant spacing, water management, fertilizer management, removal of deadhearts, field sanitation, removal of alter• nate host plants, mulching, and intercropping in the management of sorghum stem borers has been reviewed. Since the adoption of several cultural practices is either simultaneous or in close succession, it is rather difficult to ascertain the relative contribution of each practice in managing sorghum stem borers. Some commonly adopted and prevalent field and postharvest operations have been reported to contribute towards reducing the carry-over and population buildup of these pests. Since these practices do not involve much expenditure and are effective, there is a need to extend their application to farmers.

Introduction 1985). Of these, Chilo partellus, Elasmopalpus lignosellus(Pyralidae), Sesamia inferens, and Busseola Insect pests are one of the major yield-reducing fac• fusca (Noctuidae) are considered important world- tors in sorghum on a global basis. Nearly 150 species wide. have been reported to damage sorghum, both in the In an effort to control these insects, crop man- field and in storage (Seshu Reddy and Davies 1979, agement practices are particularly important. Cultur- F A O 1980). A wide range of lepidopterous stem al control of insect pests has been appropriately borers are especially damaging to sorghum and c o n • defined as the tactical use of regular farm practices stitute a major constraint in its production. This to delay or reduce insect pest attack (Seshu Reddy complex consists of 27 species spread in 10 genera of 1985). This involves the manipulation of the envir- Pyralidae and Noctuidae families (Seshu Reddy onment to make it less favorable for insect pests and

1. Professor and Head, Department of Entomology, Haryana Agricultural University, Hisar 125 004, Haryana, India. 2. Assistant Entomologist at the same location.

I C R l S A T (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, lCRlSAT Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

81 more favorable for crop g r o w t h . C u l t u r a l practices of insects are important relative factors. While the w h i c h directly or indirectly help to reduce pest d a m - dates themselves may be region-specific, time of age have become integral components of integrated sowing remains a universal cultural factor. In sor- pest management ( l P M ) because they involve no ghum specifically, adjustment of planting dates can additional expenditure and do not disturb natural be an effective method for checking the incidence of enemies of the pests. Effects of various crop man- stem borers. agement practices on incidence of stem borers in sorghum has been reviewed by many researchers, including L a w a n i (1982), Seshu Reddy (1985), and Crop Rotation Sharma(l985). C r o p r o t a t i o n w i t h non-host crops reduces pest infestation by interrupting the continuity of the food chain of oligophagous pests. The importance of this C u l t u r a l P r a c t i c e s a n d R e l a t e d practice has been supported through various re- R e s e a r c h search. For example, sorghum rotation w i t h n o n - host crops, such as groundnut, is common practice T i m e o f S o w i n g in the G a m b i a . Research has shown this practice reduces the populations of stem borers (Sesamia One effective insect control method is sowing the nonagrioides botenephaga and B. fusca) in sorghum crop so that its most susceptible g r o w t h stage coin- (Sagnia 1983). cides w i t h a time when the pest is least abundant. Chiang and Hudson (1972) reviewed population This practice has been successful in controlling data on Ostrinia nubilalis generated d u r i n g 23 con- many insect pests ( U S A : N a t i o n a l Academy of tinuous years of m o n i t o r i n g . They concluded that Sciences 1969). The importance of this practice has crop rotation was the major factor that suppressed been repeatedly documented by research. In India, a this borer population in Minnesota, U S A . greater incidence of C. partellus in sorghum sown in Other research, on the effects of lack of rotation, is J u l y than in September or October was observed. similarly conclusive. For reducing the incidence of In D e l h i , other studies have observed C. partellus to Diatraea complex in maize and sorghum, rotation cause extensive damage to sorghum sown in June w i t h non-host crop has in fact, been recommended compared w i t h that sown in July or August (Panwar in Texas ( T A M U 1979). and Sarup 1979). Taneja and Leuschner (1985) stud- Mohyuddin and Greathead (1970) observed that ied p o p u l a t i o n dynamics of C. partellus on sorghum ratooned sorghum can be a significant carryover at Hisar by m o n i t o r i n g light trap catches and larval source of stem borers, for future infestation. incidence on sorghum planted at m o n t h l y intervals. T h e highest pest incidence was observed in the crop sown d u r i n g J u l y . Singh and V e r m a (1983) also Tillage recorded seasonal incidence of C. partellus on s o r g h u m . The pest appeared t h r o u g h o u t the crop P l o w i n g after harvest is a cultural practice k n o w n to season f r o m A p r i l to August w i t h a peak infestation destroy stubble, weeds, and other alternate hosts of in the crop sown in July. At Coimbatore, Mahade- stem borers. By reducing the available host material van and Chelliah (1986b) recorded the highest inci- this practice reduces the potential for carryover. dence in terms of deadheart formation, leaf injury, W o r k i n g on sorghum in India, G a h u k a r and Jot- and stem tunneling by C. partellus in sorghum sown wani (1980) observed a reduction in population of in February and M a r c h . The least damage was re- C. Partellus and also its carryover to the next crop as corded for the crop sown in June and October. a result of off-season tillage. It was suggested that A high correlation between time of planting and this practice exposed the borers to their natural infestation has been reported by Swaine (1957), in enemies and to adverse climatic factors such as high crops attacked by B. fusca, a serious pest of sorghum temperature and low humidity. and maize in Tanzania. Crops planted early, at the In an early experiment, Du Plessis and Lea (1943) onset of the rainy season, were heavily attacked by simulated the possible effects of p l o w i n g on B. fusca the first generation larvae while later plantings lar- carryover. They buried stems containing larvae at gely escaped the damage of this pest. depths similar to those w h i c h w o u l d be achieved by It w o u l d appear that time of sowing and incidence p l o w i n g under crop residues. They observed that

8 2 moths were able to emerge f r o m depths of up to 10 has been shown that sorghum g r o w n under drought c m , but that considerable mortality occurred. stress suffers greater damage from C. partellus Recent research in Nigeria ( K a u f m a n n In press), (Sharma 1985). reported up to five times greater p o p u l a t i o n densi- Effects of soil moisture content and irrigation on ties of E. saccharina, Sesamia, Calamistis, B. fusca infestations of the lesser corn stalk borer, Elasmo- and Mythimna unipunctata in zero-tillage maize palpus lignosellus have been extensively investigated plots, compared to conventional tillage plots. In in sorghum. (Reynolds et al. 1959, All and Gallaher these trials, it was observed that mature borer larvae 1977, and A l l et al. 1979). These studies showed that often pupated in the soil at depths of less than 10 cm increased or constant soil moisture, obtained through d u r i n g the dry season and that these larvae were well-timed and regulated irrigation, deterred infesta- possibly destroyed by tillage. Similar observations tions of this borer. Use of irrigation has been sug- were made in maize by A l l et al. (1979). Infestations gested as a method to control this pest. In rainfed of the lesser corn stalk borer were greatly reduced in agriculture, however, there is little scope for manipu- no-tillage compared to conventional tillage plots. lating soil moisture except through moisture con- The incidence of corn stalk borer, Diatraea Jineolata servation. appears to increase with m i n i m u m tillage ( U S A : N a t i o n a l Academy of Sciences 1975). Similarly, M u s i c k and Petty (1973) w o r k i n g in the U S A Fertilizer Management observed that, in general, no-tillage tended to increase incidence of B. fusca and O. nubilalis in maize Fertilizer application is k n o w n to influence the sus- crop. ceptibility of crops to insects. Fertilizers enhance In contrast to what has been reported by most plant nutrition which can influence the longevity other workers, A l l and Gallaher (1977) found that and fecundity of insects, and the degree of damage infestations of lesser corn stalk borer were greatly they cause (USA: National Academy of Sciences reduced in no-tillage compared to conventional til- 1969). lage c r o p p i n g systems. Increased soil moisture was Infestations in maize of C. partellus (Singh et al. found to be an important factor prohibiting infesta- 1968, and Singh and Singh 1969), and C. partellus tion of this pest, and, that these conditions were and S. interens (Singh and Shekhawat 1964) have enhanced in the no-tillage system. In another study, been shown to increase w i t h enhanced levels of ni- Cheshire and Griffin (1985) indicated that predators trogen applied to the crop. Similar findings are of lesser corn stalk borer were much more abundant reported f o r C. partellus infestations in grain sor- in no-tillage than in conventional systems. g h u m (Starks et al. 1971). In studies conducted by Singh and Shekhawat (1964) the borer incidence in maize was not affected by different phosphate P l a n t Spacing treatments. Starks et al. (1971) working on sorghum, however, observed more C. partellus incidence when Singh (1986), found a positive correlation between both nitrogen and phosphorous fertilizers were the incidence of C. partellus and plant population used. Kalode and Pant (1967) found that maize var- per unit area in sorghum. Likewise, Chiang and ieties susceptible to C. partellus had higher nitrogen Hudson (1972) observed that with an increase in the content than resistant varieties. density of maize plants there was higher incidence of O. nubilalis. These observations suggest that higher plant density probably helps in the dispersion of Removal of Deadhearts larval populations. Zepp and Keaster (1977) reported a positive relationship between maize plant Removal and destruction of deadhearts in sorghum, density and damage incidence, caused by larvae of if carried out by farmers over large areas, has been Diatraea grandiosella. f o u n d to be a successful practice in reducing infestation of C. partellus (Seshu Reddy 1985). Destruction of central shoots showing early pinhole damage Water Management (these contain a large number of y o u n g stem borer larvae, ready for dispersal to adjacent plants) has Soil moisture may influence crop damage by insect also been f o u n d to be an effective practice (Kishore pests t h r o u g h its effect on plant vigor and g r o w t h . It and Jotwani 1982).

83 M a n a g e m e n t o f C r o p R e m n a n t s Adesiyun and A j a y i (1980) studied the effect of different practices of dealing w i t h sorghum stalks J o t w a n i and Srivastava (1982) reported the overwin- after harvest on survival of B. fusca larvae. The tering of stem borer larvae in stubbie left in the field authors observed that recommended practices of or in the harvested stems stored f o r fodder. Studies b u r n i n g stalks or spreading them in the field, were on carryover of C. partellus in different parts of not f o l l o w e d by farmers. They further observed that sorghum and maize plants d u r i n g off-season have more t h a n 9 5 % of the farmers kept their stalks in been conducted by several workers ( R e h m a n 1944, stacks, sometimes in the shade. This allowed the Singh et al. 1975, Taley and Thakare 1978, and survival of the diapausing larvae inside the stalks. Kishore and J o t w a n i 1982). A l m o s t all of them Partial burning of the stalks immediately after grain observed that carryover of the pest occurred in left- harvest (to cure t h e m for use as fuel) was f o u n d to over stubble and stalks. k i l l 9 5 % of the larvae w i t h no damage to the stalks. This practice has been recommended as a c o m p r o - mise to complete b u r n i n g and allows farmers to Field Sanitation utilize the stalks for building, fencing, and fuel.

This pratice involves the removal or destruction of crop residues, weeds, and nearby w i l d host plants to Mulching eliminate a pest by destroying its f o o d and shelter. As w i t h tillage, this practice is intended to reduce the In Uganda, nontreated crop residues are often used ability of insects to carryover to the next season. to m u l c h the next sorghum crop. Subsequent levels A c c o r d i n g to A i k i n s (1957), economically important of stem borer infestation have been f o u n d to be far stem borers on sorghum in Ghana, Sesamia sp, higher than normal for the area (Mohyuddin and Eldana sp. and Busseola sp., survive the dry spell by Greathead 1970). Research by G i l l (1963) observed finding fresh cereal or grass g r o w t h suitable for o v i - that m u l c h i n g increased the incidence of stem borer position and on which the newly hatched larvae can Chilo infescatellus in the ratoon crop of sugarcane. subsequently feed. He suggested that grasses, stub- In maize, research has shown that mulches of wheat ble, and pieces of sorghum stems left after harvest be and rye residue provide feed to lesser corn stalk destroyed because this material provides a medium larvae, w h i c h diverts them f r o m attacking the maize to sustain populations of these pests. crop (Cheshire and A l l 1979). In Tanzania, Duerden (1953) achieved nearly complete eradication of C. partellus and B. fusca on sorghum and maize f o l l o w i n g burning of stubble Intercropping and crop residues. I n g r a m (1958) and Nye (1960) recorded considerable reductions C. partellus and The principle of controlling insect pest populations B. fusca populations at the beginning of the sorghum- by increasing the diversity of an agroecosystem has g r o w i n g season, f o l l o w i n g destruction of all crop been discussed by many authors, including, Smith residues and w i l d species of sorghum around culti- (1972) and S o l o m o n (1973). Intercropping has some vated areas in East Africa. potential as a cultural method to control stem borer M o s t stem borers have w i l d plant hosts in addi- infestation of sorghum. t i o n to their cultivated hosts (Jepson 1954). Seshu G r o w i n g sorghum in association w i t h other crops Reddy and Davies (1980) reported five cultivated has been shown to reduce C. partellus damage on and ten w i l d plants as hosts of C. partellus in India. s o r g h u m , mungbean, urd bean, pigeonpea (Singh W o r k i n g in Botswana, R o o m e (1976) observed and Singh 1974); cowpea ( O m o l o and Seshu Reddy Sudan grass to be heavily infested w i t h C. partellus. 1985, and Mahadevan and C h i l l i a h 1986a); lablab Sesamia sp also has many graminaceous hosts bean ( M a h a d e v a n and Chelliah 1986a, and Sadaka- including elephant grass, buffalo grass, and finger thulla and M a n i 1978). C h a n d and Sharma (1977) millet ( I n g r a m 1958). also f o u n d that g r o w i n g maize in association w i t h Research has brought recognition to the i m p o r - legumes reduced C. partellus damage on maize. tance of field sanitation as a cultural practice to Research has shown that intercropping of maize and reduce stem borer infestations. Destruction of crop sorghum without association with a cereal crop gives residues and other potential host carryover material rise to higher incidence of C. partellus (Singh and has been widely recommended. Singh 1974). Other research by A m o a k a - A t t a et al.

8 4 (1983) reported that the incidence of C. partellus, Cheshire, J.M., and Griffin, J. 1985. Evidence that mulch B. fusca, E. saccharins and S. calamistis in trials of density influences lesser c o r n stalk borer damage to n o - sorghum and maize monocrops, and maize/sor- tillage grain sorghum. Sorghum Newsletter 27:61.

g h u m dicrops, was earlier than in trials intercrop- Chiang, H.C.,and Hudson, A.C. 1972. Population fluctua- p i n g these cereals w i t h cowpea, w h i c h showed a tions of the European c o r n borer, Ostrinia nubilalis, at significant delay in borer colonization. Waseca, Minnesota, 1940-70. Environmental Entomology 1:7-16.

Duerden, J.C. 1953. Stem borers of cereal crops at D i s c u s s i o n a n d C o n c l u s i o n s Kongwa, Tanganyika, 1950-52. East African Agricultur a l Journal 19:105-119. As wide-scale practices, postharvest tillage, chop- Du Plessis, C., and Lea, H.A.F. 1943. The maize stalk ping and storing sorghum stalks in small pieces, borer Calamistis fusca (Hampsn.) Bulletin of the Depart- removal of deadhearts, partial b u r n i n g of the stalks, ment of Agriculture and Forestry, Union of South Afr i c a and destruction of stalks and stubble have all been no.238. 51 p p . f o u n d effective as cultural practices in reducing F A O . 1980. Elements of integrated control of sorghum borer populations. T i m e of sowing, crop rotation, pests. FAO Plant Production and Protection Pages no. 19. tillage, plant spacing, water and fertilizer manage- Rome, Italy: FAO. 159 pp. ment, m u l c h i n g , and intercropping all contribute useful practices w h i c h also afford cultural control of Firke, P.V., and Kadam, M.V. 1978. Studies on the sea- sorghum stem borers. sonal incidence of the j o w a r stem borer, Chilo zonellus Swinhoe. Journal of Maharashtra Agricultural Universi- ties 3:141-142.

Gahukar, R.T., and Jotwani, M.G. 1980. Present status of R e f e r e n c e s field pests of s o r g h u m and millets in I n d i a . T r o p i c a l Pest Management 26:128-151. Adesiyun, A . A . , and Ajayi, O. 1980. C o n t r o l of the Gill, M . S . 1963. Effect of trash mulch on the growth and s o r g h u m stem borer, Busseola fusca, by partial burning of yield of ratoon crop of sugarcane. West Pakistan Journ a l the stalks. T r o p i c a l Pest M a n a g e m e n t 26:113-117. of Agricultural Research 1:149-156. Aikins, J.S. 1957. Dry season investigation of the stem Ingram, W.R. 1958. The lepidopterous stalk borers asso- borers, northern region (Ghana). Ghana Farmer ciated with Gramineae in Uganda. Bulletin of Entomolo g i - 1:190-191. cal Research 49:367-383. A l l , J . N . , and Gallaher, R . N . 1977. Detrimental impact of Jepson, W.F. 1954. A critical review of the world literature no-tillage c o r n c r o p p i n g systems i n v o l v i n g insecticides, on the lepidopterous stalk-borers of tropical graminaceous hybrids a n d i r r i g a t i o n on lesser c o r n stalk borer infesta- crops. London, UK: Commonwealth Institute of Entomol - tions. J o u r n a l o f E c o n o m i c E n t o m o l o g y 70:361-365. ogy. 127 pp. A l l , J . N . , Gallaher, R . N . , and Jellum, M . D . 1979. I n f l u - Jotwani, M.G., and Srivastava, K.P. 1982. Insect pests on ence of p l a n t i n g date, p r e p l a n t i n g weed c o n t r o l , i r r i g a t i o n forage sorghum and their control. Forage Research and conservation tillage practices on efficacy of p l a n t i n g 7A:129-139. time insecticide applications f o r c o n t r o l of lesser cornstalk borer i n f i e l d c o r n . J o u r n a l o f E c o n o m i c E n t o m o l o g y Kalode, M.B., and Pant, N.C. 1967. Studies on the amino 72:265-268. acids, n i t r o g e n , sugar and moisture content of maize a n d s o r g h u m varieties and their relation to Chilo zonellus Amoako-Atta, B., Omolo, E.O., and Kidega, E.K. 1983. (Swin.) resistance. Indian Journal of Entomology Influence of maize, cowpea, and sorghum intercropping 29:139-144. systems on stem-/pod-borer infestations. Insect Science a n d its A p p l i c a t i o n 4 ( l - 2 ) : 4 7 - 5 7 . K a u f m a n n , T. ( I n press.) The behavioural biology, feeding habits a n d ecology of three species of maize stem borers, Chand, P., and Sharma, N . N . 1977. Influence of c r o p Eldana saccharina, Sesamia calamistis and Busseola fusca association on insect pest incidence. Proceedings of the in Ibadan, Nigeria. Annals of the Entomological Society of I n d i a n N a t i o n a l Science A c a d e m y 43:108-114. A m e r i c a . Cheshire, J . M . , and A l l , J . N . 1979. Feeding behaviour of Kishore, P., and Govil, J.N. 1982. Utilization of host plant lesser c o r n stalk borer larvae in simulations of no-tillage, resistance for judicious use of insecticides in sorghu m . mulched conventional tillage, and conventional tillage Agriculture Science Digest (2):101-104. corn cropping systems. Environmental Entomology 8:261-264.

85 Kishore, P., and Jotwani, M . G . 1982. Integrated pest man- Sagnia, S.B. 1983.Possible integrated pest management agement in sorghum. Journal of Environmental Research tools f o r the effective c o n t r o l of cereal stem-borers in the 3(1):1-7. G a m b i a . Insect Science a n d its A p p l i c a t i o n 4 ( 1 - 2 ) : 217-219. Lawani, S . M . , 1982. A review of the effects of various a g r o n o m i c practices on cereal stem borer p o p u l a t i o n s . Seshu Reddy, K.V. 1985. Integrated approach to the con- T r o p i c a l Pest M a n a g e m e n t 28:266-276. t r o l of s o r g h u m stem borers. Pages 205-215 in Proceedings of the International Sorghum Entomology Workshop, 15- Mahadevan, N . R . , and Chelliah, S. 1986a. Influence of 21 Jul, 1984, College Station, Texas, USA. Patancheru, intercropping legumes with sorghum on the infestation of A. P. 502 324, India: International Crops Research Insti- the stem borer, Chilo panellus ( S w i n h o e ) in T a m i l N a d u , tute for the Semi-Arid Tropics. India. Tropical Pest Management 32(2): 162-163. Seshu Reddy, K.V., and Davies, J.C. 1979. Pests of M a h a d e v a n , N.R., and Chelliah, S. 1986b. Influence of s o r g h u m and pearl millet, a n d their parasites and predators season and weather factors on the occurrence of the recorded at ICRISAT Center, India, up to August 1979. s o r g h u m stem borer Chilo partellus ( S w i n h o e ) in T a m i l Cereal Entomology Progress Report no.2. Patancheru, N a d u . T r o p i c a l Pest M a n a g e m e n t 32(3):212-214. A.P. 502 324, India: International Crops Research Institute Mohyuddin, A.I.,and Greathead, D.J. 1970. An annotated for the Semi-Arid Tropics. 23 pp. (Limited distribut i o n . ) list of the parasites of graminaceous stem borers in East Seshu Reddy, K.V.,and Davies, J.C. 1980. S o r g h u m stem A f r i c a w i t h a discussion of their po te nt i a l in biological borer Chilo partellus Swinhoe-recent findings at ICRISAT control. Entomophaga 15:241-274. Center. Presented at the All India Coordinated Sorghum Mustek, G J . , and Petty, H . B . 1973. Insect control in con- Improvement Project Workshop, 12-14 May 1980, Coim- servation tillage systems. Pages 120-125 in Conservatio n batore, Tamil Nadu, India. tillage: proceedings of a N a t i o n a l Conference, A n k e n y , Sharma, H . C . 1985. Strategies f o r pest c o n t r o l in s o r g h u m , Iowa, USA. Ankeny, Iowa, USA: Soil conservation society India. Tropical Pest Management 31:167-185. o f A m e r i c a . Singh, B., Battu, G.S., Dhaliwal, J.S., and Atwal, A. S. N y e , I . W . B . 1960. T h e insect pests of graminaceous crops 1975. Population studies on the maize stem borer, Chilo in East A f r i c a . C o l o n i a l Research S t u d y n o . 3 1 . L o n d o n , partellus (Swinhoe) in Punjab. l.Mode of overwintering U K : Her Majesty's Stationery Office. 48 pp. larvae. Indian Journal of Entomology 37:132-136. O m o l o , E.O., and Seshu Reddy, K . V . 1985. Effects of Singh, K.M., and Singh, R.N. 1974. The population build different s o r g h u m based c r o p p i n g systems on insect pests up of Pyrilla perpusilla (Walker) on sorghum and pearl in Kenya. Pages 395- 401 in Proceedings of the Interna- millet under dryland conditions at Delhi. Indian Journa l of t i o n a l S o r g h u m E n t o m o l o g y W o r k s h o p , 15-21 J u l 1984, Ecology 1:12- 16. College Station, Texas, USA. Patancheru, A.P. 502 324, India:International Crops Research Institute for the Se m i - Singh, S.P. 1986. Screening of forage sorghum genotypes A r i d T r o p i c s . f o r resistance to shoot fly, Athericona soccata (Rondurn) and stem borer, Chilo partellus ( S w i n h o e ) and estimation Panwar, V.P.S.,and Sarup, P. 1979. Relationship between of avoidable losses. Ph.D. thesis, Haryana Agricultura l successive dates of sowing of maize and damage caused by University, Hisar, Haryana, India. 135 pp. Chilo partellus (Swinhoe) affecting grain yield. Journal of E n t o m o l o g i c a l Research 3:9-24. Singh, S.P., and Verma, A.N. 1983. Seasonal incidence of stem borer, Chilo partellus (Swinhoe) in forage sorghum R a h m a n , K . A . 1944. Biology and control of maize and varieties. A n n u a l Progress R e p o r t of the A l l India C o o r d i - J o w a r borer, (Chilo zonellus Swin.). I n d i a n J o u r n a l of nated Project for Improvement of Sorghum (Forage). Agricultural Science 14:303-307. Hisar, Haryana, India: Haryana Agricultural University. Reynolds, H.T., Anderson, L.D., and Andres, L.A. 1959. 32 pp. C u l t u r a l a n d chemical c o n t r o l of the lesser c o r n stalk borer Singh, T.P., and Singh, R. 1969. Incidence of stem borer i n southern C a l i f o r n i a . J o u r n a l o f E c o n o m i c E n t o m o l o g y ( C h i l o zonellus Swinhoe) and lodging in J a u n p u r variety of 52:63-66. maize under different levels of nitrogen. Indian Journ a l of R o o m e , R . E . 1976. Resistance in s o r g h u m varieties to Entomology 31:158-160. attack by larvae of Chilo partellus Swinhoe ( S o r g h u m stalk Singh, T.P., Singh, R., and Chaudhary L.B. 1968. Inter- borer). Pages 111-115 in Crop protection in Botswana: relation of stem borer incidence and certain agronomi c biennial report 1971-73. G a b o r o n e , Botswana: M i n i s t r y of traits in J a u n p u r variety of maize under different levels of A g r i c u l t u r e , D i v i s i o n o f A g r i c u l t u r a l Research. nitrogen. Indian Journal of Entomology 30:220-222. Sadakathulla, S., and Mani. M. 1978. Influence o f inter- c r o p p i n g on the incidence of s o r g h u m pests. S o r g h u m Newsletter 21:70.

8 6 Singh, U.C., Misra, U.S.,Dhamdhere,S.V.,and Dwivedi, V . S . 1985. C a r r y o v e r of the s o r g h u m stalk borer, Chilo partellus (Swinhoe) in off-season in different crops. J o u r - nal of E n t o m o l o g i c a l Research 9:170-173.

Singh, V . B . , and Shekhawat, G.S. 1964. Incidence of stem borers in maize under different fertility levels. I n d i a n J o u r - nal o f A g r o n o m y 9:48-50.

S m i t h , R . F . 1972. T h e impact of the Green R e v o l u t i o n on plant protection in t r o p i c a l a n d subtropical areas. B u l l e t i n of the E n t o m o l o g i c a l Society of A m e r i c a 18: 7-14.

Solomon, M . C . 1973. Ecology in relation to the management of insects. Pages 153-167 in Insects: studies in p o p u - l a t i o n management (Geier, E . D . P . W . , C l a r k , L . R . , A n d e r s o n , D . J . , and N i x , H.A., eds.). C a n b e r r a , A u s t r a l i a : Ecological Society of A u s t r a l i a .

Starks, K.J., Schumaker, G.,and Eberhart, S. A. 1971. S o i l fertility and damage by Chilo zonellus on grain sorghum. J o u r n a l o f E c o n o m i c E n t o m o l o g y 64:740-743.

Swaine, G. 1957. The maize and s o r g h u m stalk borer, Busseola fusca (Fuller), in peasant agriculture in Tanga- n y i k a T e r r i t o r y . Bulletin o f E n t o m o l o g i c a l Research 48:711-722.

Taley, Y.M.,and Thakare, K.R. 1978. Studies on the c a r r y - over of Chilo partellus S w i n . t h r o u g h s o r g h u m stubbles. S o r g h u m Newsletter 21:52.

T A M U (Texas A & M University). 1979. Insect and mite pests of grain s o r g h u m management approaches. Texas Agricultural Extension Service no.B-1220. College Sta• t i o n , Texas, U S A : T A M U . 2 4 p p .

U S A : National Academy of Sciences. 1969. Insect-pest management and c o n t r o l . N A S P u b l i c a t i o n no. 1695. N a t i o n a l A c a d e m y of Sciences.

U S A : National Academy of Sciences, 1975. Pest control: an assessment of present and alternative technologies, V o l . 2 . I I . C o r n / soybeans pest c o n t r o l : team study o n p r o b - lems o f pest c o n t r o l . W a s h i n g t o n , D . C . , U S A : N a t i o n a l A c a d e m y of Sciences.

Z e p p , D . B . , and Keaster, A . J . 1977. Effects of c o r n plant densities on the g i r d l i n g behaviour of the south-western borer. J o u r n a l o f E c o n o m i c E n t o m o l o g y 70:678-680.

8 7

Biological Control of Sorghum Stem Borers

M. Betbeder-Matibet1

Abstract

All the sorghum stem borers are polyphagous Pyralids and Noctuids which attack most tropical cereals. In developing countries, the biological control of these pests is directed at rice, maize, or sugarcane rather than sorghum. Attempts have been made to reduce their population levels by releasing indigenous or introduced natural enemies. Several species ha ve now become established although little is known about the economic implications of these introductions. The potential use of pathogens in the biological control of stem borers is also discussed.

Introduction are f o u n d in A f r i c a south of the Sahara and tolerate d r y or wet seasons. Severe damage has been caused by Chilo partellus in Nepal, South A f r i c a and in all In all the regions of the w o r l d where sorghum is the Indian climatic regions. cultivated, this graminaceous crop is attacked by Sesamia calamistis and E. saccharina multiply lepidopterous stem borers. These are Pyralidae or t h r o u g h o u t the year and their successive generations Noctuidae which are generally polyphagous. The attack cultivated host plants d u r i n g the rainy sea• species of genera Chilo, Sesamia, and Diatraea, son (s), then survive on w i l d grasses. Other stem bor• cited by Seshu Reddy (1985), attack at least three of ers enter into diapause or quiescence w i t h the onset the m a i n graminaceous crops throughout the tropics of the dry season, such as Busseola fusca, Acigona and subtropics (rice, corn, millet, sorghum, and ignefusalis, C. partellus, or D. saccharalis. sugar cane) and also find suitable hosts in many w i l d Several species of sorghum stem borers can cohabit grasses. M o s t of these insects survive under wide- the same plant, w i t h some attacking young stems ranging climatic conditions and have been recorded and others concentrating around the plant inter- t h r o u g h o u t the tropic and semi-tropic regions of the nodes and ears. This location specificity causes dif• w o r l d . ferent kinds of damage: the stem is destroyed Diatraea saccharalis is present in the southern because the central shoot is killed, causing dead- region of United States, and in Central and South heart, or the stem is b r o k e n at the level of a bored A m e r i c a . Eldana saccharina and Sesamia calamistis internode; or the productivity of the ear is reduced

I. I R A T / C I R A D , BP 5035 - 34032 Montpellier Cedex, France. lCRISAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, ICRISAT Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

89 because the host plant is weakened or because a part Table 1. Parasites of sorghum stem borers. of the ear has been directly destroyed by larvae. Species of stem borers1 Agricultural research and development institu- Families o f tions, w i t h a mandate to i m p r o v e s o r g h u m produc- parasites CP BF SSP ES D S t i o n techniques and insect-pest management in Braconidae 14 8 4 1 21 developing countries, have directed efforts t o w a r d Ichncumonidae 9 6 4 2 3 an integrated approach, particularly one which Trichogrammatidae 1 - - 2 5 incorporates biological controls. Pteromalidae - - 1 - 2 E u l o p h i d a e 3 3 2 2 1 Eurytomidae 1 - - 1 1 - - R e s u l t s o f B i o l o g i c a l C o n t r o l o f Eupelmidae - - 2 Chalcididae 3 1 2 2 1 S o r g h u m S t e m B o r e r s Scelionidae 1 2 1 1 1 Bethylidae 2 -- 2 1 C o n d i t i o n s o f B i o - c o n t r o l A t t e m p t s Tachinidae 7 10 3 7 10

1. CP = Chilo partellus; BF = Busseola fusca; S S P = Sesamia sp; ES Biological c o n t r o l of sorghum stem borers has often = Eldana saccharina; a n d DS = Diatraea saccharalis. been considered to be part of a strategy f o r g r a m i - naceous c r o p protection in tropical countries. F o r example, the purpose of most introductions of parasites of D. saccharalis has been to protect sugar cane against this stem borer in many countries of the are c o m m o n parasites to at least t w o of five main A m e r i c a n continent. In the same way, attempts to A f r i c a n stem borers. These data clearly show that establish natural enemies of C. partellus in I n d i a and the possibilities of i n t r o d u c i n g more exotic parasites A f r i c a had the p r i m a r y objective to c o n t r o l this stem of graminaceous stem borers are not exhausted, borer in maize plantations. But biological control even if previous attempts have not proven successful also involves safeguarding or enhancing indigenous in I n d i a , A m e r i c a , and A f r i c a . beneficial insects, so any changes in agronomic prac- Scant i n f o r m a t i o n is available on other stem borer tices influencing their well-being warrants study. predators. M a n y species of ants are predators of eggs and newly hatched larvae of E. saccharina (Betbeder-Matibet 1983; Leslie 1982; and G i r l i n g Biological Control with 1978). Sharma and Sarup (1979) reported the role of Entomophagous Insects different spiders and Seshu Reddy (1981) the c o n t r i - b u t i o n of ants, ladybird beetles, and earwigs in k i l - Parasites a n d P r e d a t o r s ling populations of C. partellus. Temerak (1983) reported that several soil-inhabiting predators des- M a n y parasites of different families have been troy n y m p h a l populations of Sesamia cretica. recorded in Asia, A f r i c a , and the Americas f r o m the f i v e m a i n s o r g h u m stem b o r e r s : C. partellus, B. fusca, Sesamia spp, E. saccharina, and D. sac- Review of Some Bio-control Attempts charalis (Table 1). Three families of larval parasites predominate: Braconidae, Ichneumonidae, and On the A me rican continent, various attempts of bio• Tachinidae. logical control with parasites were made in different Braconids account for 3 5 % of parasites recorded sugarcane areas d u r i n g the last 30 years to c o n t r o l on C. partellus and 4 5 % of parasites f o u n d on D. saccharalis. Few were successful. T w o notable D. saccharalis. O n l y 4 out of 48 species of this family successes were obtained w i t h Lixophaga diatraeae, w h i c h have been identified, are recorded as parasites w h i c h became established in some Caribbean Is- of t w o stem borer species, at least a m o n g the five lands, and A. flavipes, w h i c h became established in cited above. O n l y three species, after their introduc- Barbados, S o u t h A m e r i c a , and the U n i t e d States. t i o n and their establishment, are actually present in A l t h o u g h these introductions were designed f o r t w o regions : A f r i c a and America. integrated protection of sugarcane plantations, sor- In A f r i c a , 5 of 11 braconid species, 3 of 9 ichneu- g h u m cultures have benefitted f r o m these parasite m o n i d species, and 6 of 11 tachinid species recorded releases.

9 0 In A f r i c a , attempts to introduce enemies of grami- situations and cause an unexpected multiplication of naceous stem borers have met w i t h varying success a pest. d u r i n g the last 20 years. In Kenya, Uganda, and As we k n o w , the graminaceous stem borer p o p u - Tanzania, several species of Trichogrammatidae, lations can be decimated by parasites and predators. Braconidae, Ichneumonidae, and Tachinidae have Several authors note that ants and spiders are p r i n - been i m p o r t e d f r o m India and released. None have cipally responsible for the m o r t a l i t y (sometimes been recovered (Ingram 1983). In South Africa, exceeding 90%) of eggs and newly hatched larvae of A. flavipes was introduced recently (Zkoroszewski Pyralidae and Noctuidae. F o r example Leslie (1982) and V a n H a m b u r g 1987) then released in maize and notes that 6 0 % of E. saccharina eggs are killed in s o r g h u m infested by C. partellus and B. fusca. This experimental plots without soil treatment while only braconid was recovered on both pests, some years 19% mortality occurs in plots w i t h soil treatment. after releasing, but apparently has not been able to In B u r k i n a Faso, a nematicide experiment on maintain populations. U n l i k e Apanteles sesamiae, it plantation sugarcane confirmed the prominent part seems that A. flavipes has not endured the climatic played b y predators i n the n a t u r a l c o n t r o l o f conditions of austral winter. E. saccharina. Table 2 shows various soil treatments Some indigenous parasites have been f o u n d to applied in a randomized experiment and 12 months reduce larval and n y m p h populations of E. sacchar- later, percentages of bored internodes in the plots. ina (Betbeder-Matibet 1983). But most laboratory These percentages reveal survival rates of E. sacchar- tests w i t h other parasites of pyralidae were failures. ina populations after egg incubation, and the devel- The braconids A. flavipes, Apanteles chilonis or opment of newly hatched larvae before stalk inter- Bracon chinensis, the techinids L. diatraeae, Stur- node penetration. miopsis inferensor Metagonistylum minense do not The nontreated control percentage (3.9%) is equal thrive on larvae of this A f r i c a n stem borer. The to the infestation level in sugarcane plantations in nymphs of E. saccharina are well-protected by a the experiment area. With methyl bromide applied thick cocoon and are not parasitized by the eulophid under a sheet, biological activity is stopped. In this Pediobus furvum. case, 21.8% of plant internodes were bored. With the In Madagascar and in the Mascareignes Islands, other three soil treatments, damage by E. saccharina the sorghum stem borers C. partellus, C. orichalcoci- is more serious than in the nontreated c o n t r o l only liellus, and S. calamistis are f o u n d . Here and on the when nematicides are applied at high rates. continent, their populations are decimated by a This experiment has indicated the real importance cohort of indigenous parasites ( A p p e r t and R a n a i - of natural control of eggs and newly hatched larvae vosoa 1971). But several exotic parasites, have also of this stem borer. Without soil predators, damage been introduced, released, then recovered ( A p p e r t , to sugarcane can be five times greater. In sorghum et al. 1969). A. sesamiae, f r o m M a u r i t i u s , has been released in Madagascar and R e u n i o n where it became established, p a r a s i t i z i n g the larvae of S. calamistis. F r o m Uganda, P. furvum, has been 1 released in Madagascar, Reunion, and the Comores Table 2. Incidence of soil treatment on natural control of Islands. N o w it is recovered f r o m n y m p h s of Eldana saccharina. S. calamistis and C. partellus. The eulophids Tri- % Bored chospilus diatraeae and Tetrastichus israeli were Treatment (a.i. m- 2 ha-1) 2 internodes3 also released in Reunion and recovered on the pink M e t h y l b r o m u r e 100 g m - 2 21.8 borer S. calamistis. A l d i c a r b e 4.0 k g h a - 1 4.9 Phenamiphos 2.8 k g ha-1 4.1 Phenamiphos 5.6 k g h a - 1 3.9 Importance of the Safety of Beneficial Phenamiphos 8.4 k g h a- 1 9.9 Organisms C a r b o f u r a n 3.0 k g ha-1 5.2 C a r b o f u r a n 6.0 k g h a- 1 7.1 1 Outbreak of insect infestations in the field is often C a r b o f u r a n 9.0 k g ha- 8.0 Untreated c o n t r o l 3.9 the result of h u m a n interventions w h i c h m o d i f y the - biological balance of the agrobiocoenose. N ew var- 1. ln a n e m a t i c i d e e x p e r i m e n t on sugarcane. 2 ieties, cultural practices, or a decision to use chemi- 2 . A c t i v e i n g r e d i e n t a p p l i e d o n 1 m o r 1 ha. 3. A v e r a g e of 6 r e p l i c a t i o n s of 20 stalks each. cal control, for example, can create new ecological

9 1 stem borer management, conservation of useful soil tions of stem borers in A f r i c a (Chilo partellus, Chilo fauna should be a recognized precaution before con- zacconius, and Sesamia calamistis) but their epide- sidering transfer and release of imported natural miology and their relative efficiency have not been enemies into sorghum areas. studied. While some excellent work has been carried out on biological controls of sorghum stem borers, their predators and diseases (which can k i l l more Biological Control with Fungal, than 9 0 % of borer populations) have been largely B a c t e r i a l , a n d V i r a l Diseases neglected. Insect pest management research in these areas needs amplification. Few diseases have been identified on sorghum stem borers and their value as biological control agents is generally u n k n o w n . A few examples of recent re- R e f e r e n c e s search in this area are given below. Some laboratory and field experiments have been Appert, J., Betbeder-Matibet, M., and Ranaivosoa, H. carried out to evaluate the pathogenic behavior of 1969. Vingt annees de lutte biologiquea Madagascar. (In fungal, bacterial, and viral diseases. The effect of a Fr. Summaries in E n , Es.) A g r o n o m i c Tropicale 24 chromogenic strain of Serratia marcescenswas stud- (6-7):555-572. ied on C. partellusin India (Chakravorty et al. 1983). Appert, J., and Ranaivosoa, H. 1971. Un nouveau succes A single application of the cell suspension of the de la lutte biologique a Madagascar: controle des foreurs bacterium prevented eggs f r o m hatching and killed de la tige de mais par un parasite i n t r o d u i t ; Pediobius newly hatched larvae. Sinha and Prasad (1975) t h i n k furvus G a h a n . ( H y m . Eulophidae). ( I n Fr. Summaries in that t o x i n of Fusarium aleyrodis could be used En, Es.) Agronomie Tropicale 26(3):327-331. against this stem borer. Betbeder-Matibet, M. 1983. Eldana saccharina W a l k e r Interactions between parasitoids and pathogens ( L e p . , Pyralidae), foreur de tiges de la canne a sucre en in the same host have also been observed, in order to Afrique. (In Fr.) Docteur Ingenieur thesis, Ecole Nationale k n o w if there is synergy or competition between Superieure d ' A g r i c u l t u r e d e M o n t p e l l i e r ( E N S A M ) , parasites. This w o r k is underway w i t h S. calamistis M o n t p e l l i e r , France. 192 pp. w i t h A. sesamiae and t w o viruses. Other laboratory Chakravorty, B.P., Kundu, G.G., Hegde, S.V., and trials have been undertaken to investigate the trans- Sharma, J.K. 1983. Effect of Serratia marcescens Bizio f o r mission of pathogens by parasitoids, for example, in the c o n t r o l of s o r g h u m stem borer, Chilo partellus ( S w i n - Sesamia cretrca (Temerak 1982). hoe). I n d i a n J o u r n a l of E n t o m o l o g y 45(4):456 458. In northern Florida, Funderburk et al. (1984) report granulosis virus and Beauveria sp on larval Funderburk, J.E., Boucias, D . G . , Herzog, D . C . , Sprenkel, R.K.,and Lynch, R.E. 1984. Parasitoids and pathogens of Elasmopalpus lignosellus. In R e u n i o n , a viral c o m - larval lesser cornstalk borers (Lepidoptera: Pyralidae) in plex, including nuclear and cytoplasmic polyhedro- northern Florida. Environmental Entomology sis viruses, has been detected on S. calamistis larvae. 13:1319-1323. But very few pathogens have been tested under field conditions and the experiments noted here have Girling, D.J. 1978. The d i s t r i b u t i o n and biology of Eldana saccharina W a l k e r ( L e p i d o p t e r a : Pyralidae) and its rela- not yet resulted in an improvement of integrated pest tionship to other stem borers in Uganda. Bulletin of E n t o - management programs in sorghum. mological Research 68:471-488.

Ingram, W . R . 1983. Biological control of graminaceous Conclusions stem-borers and legume pod-borers. Insect Science and its Application 4(1-2):205-209.

Resources allocated for biological control of grami- Leslie, G . W . 1982. A study of egg predators of Eldana naceous stem borers, and especially sorghum stem saccharina Walker (Lepidoptera: Pyralidae). Proceedings, borers in tropical countries, have been too small to S o u t h A f r i c a n Sugar Technologists' Association 1-3.

permit a good survey of natural enemies. While a Seshu Reddy, K.V. 1983. Studies on the stem borer c o m - number of parasites of eggs, larvae, and pupae of plex of sorghum in Kenya. Insect Science and its Applic a - these stem borers are k n o w n , very few predators and tion 4(1-2):3-10. pathogens have been identified. N o r has their efficacy been tested against pyralids and noctuids. We k n o w that many nosema diseases destroy popula-

9 2 Seshu Reddy, K.V. 1985. Integrated approach to the con- t r o l of s o r g h u m stem borers. Pages 205-215 in Proceedings o f the I n t e r n a t i o n a l S o r g h u m E n t o m o l o g y W o r k s h o p , 15-21 J u l 1984, College S t a t i o n , Texas, U S A . Patancheru, A . P . 502 324, I n d i a : I n t e r n a t i o n a l Crops Research Insti- tute f o r the S e m i - A r i d Tropics.

Sharma, V . K . , and Sarup, P. 1979. Predatory role of spiders in the integrated c o n t r o l of the maize stalk borer, Chilo partellus Swinhoe. Journal of Entomological Research 3:229-231.

Sinha, S.K.,and Prasad, S . M . 1975. A biological approach to the c o n t r o l of maize borer, Chilo zonellus Swinhoe. C u r r e n t Science 44:197-198.

Temerak, S.A. 1982. Ubertragung zweier bakterieller path- ogene in den k o r p e r v o n Sesamia oretica Led. (Lep. Tortri- cidae) mittels des legebohrers v o n Bracon brevicornis W e s m . ( H y m . , Braconidae). ( I n D l . ) Anzeiger fuer Schaed- lingskunde Pflanzenschutz Umweltschutz 55:89-92.

Temerak, S.A. 1983. A p r e l i m i n a r y survey on the soil inhabiting predacious arthropods associated with pupae of the large sugarcane borer, Sesamia cretica L e d . in s o r g h u m field. Bulletin de la Societe Entomologique d'Egypte 62:251-255.

Zkoroszewski, R.W., and van Hamburg, H. 1987. The release of Apanteles flavipes (Cameron) (Hymenoptera: Braconidae) against stalk borers of maize and g r a i n sorghum in South Africa. Journal of the Entomological Society of Southern Africa 50(1):249-255.

Assessment of Yield Loss of Sorghum and Pearl Millet due to Stem Borer Damage

S.L. Taneja1 and K.F. Nwanze2

Abstract

The stem borer species that infest sorghum and pearl millet are listed. At 1CRISA T Center in India, loss in grain yield due to C h i l o partellus damage in sorghum was estimated by two methods. These experiments involving the phased use of carbofuran, or artificial infestation using laboratory-reared first instar larvae showed that maximum grain yield loss occurred when infestation took place 15-30 days aftercrop emergence. The maximum number of deadhearts was formed when infestation took place during this period. Stem tunneling caused by later infestations did not cause a reduction in grain yield. In two studies at the l C R l S A T Sahelian Center in Niger, results showed that under low levels of borer infestation (caused by Coniesta ignefusalis), a nonprotected pearl millet crop gave slightly higher yields than one that was protected by insecticide. In a date of sowing trial losses were heavier on late-sown millet with an increase in proportion of nonproductive tillers. Yield loss caused by other borer species are also discussed.

1. Entomologist, Sorghum Group, Cereals Program, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Andhra Pradesh 502 324, India. 2. Principal Cereals Entomologist at the same location. l C R l S A T Conference Paper no. CP 495.

ICRISAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, ICRISAT Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

9 5 Introduction infestation at Hisar, I n d i a , f r o m 1982 to 1985. The second experiment was conducted at ICRISAT O u t of 27 species of stem borers that attack sorghum Center in 1985 and 1986. Eggs and larvae were crops, Chilo partellus Swinhoe is the predominant obtained from ICRISAT's insect rearing laboratory, species in Asia and East A f r i c a . Prominent in other where the insect is reared on artificial diet. regions are: Busseola fusca Fuller, Sesamia calamistis H a m p s o n , and Eldana saccharina W a l k e r in Natural infestation. N a t u r a l infestation of stem A f r i c a ; Sesamia cretica Laderer in Mediterrarean borer at Hisar is usually severe on sorghum planted Europe and the M i d d l e East; and Diatraeaspp in the d u r i n g the first half of July (Taneja and Leuschner southern U.S., M e x i c o , and New W o r l d Tropics 1985). S o r g h u m was sown f o r these trials d u r i n g this ( Y o u n g 1970, F A O 1980). In pearl millet, the pre- period in each of the study years. D u r i n g 1982-83, d o m i n a n t species of stem borer is Coniesta (A c i g - only genotype C S H 1 was used. In 1984, three geno- ona) ignefusalis H a m p s o n , w h i ch is a major pest in types, C S H 1, I C S V 1, and IS 2205 were used, and in West Africa. 1985 t w o genotypes, I C S V 1, and PS 28157-1 were Assessment of crop losses due to insect attack is included. Planting was done in 8-row plots of 4 m essential in determining pest status, economic thresh- length. In 1982 and 1983, a randomized block design old levels, and suppression strategy options for pest was used, while in 1984 and 1985 a split plot design c o n t r o l . It is also a tool in decision m a k i n g in agri- was used w i t h genotypes as main plots. cultural planning and forecasting. A l t h o u g h severe C a r b o f u r a n granules (2 g meter r o w-1 ) were ap- stem borer infestations in sorghum and pearl millet plied at 15, 30, and 45 days after emergence ( D A E ) in have been reported f r o m a number of locations, various combinations to obtain the protection levels there are no reliable qualitative estimates of resul- indicated in Tables 1-3. T o t a l number of plants and tant crop losses. Several methods have been used in those showing deadhearts in the central f o u r rows of an attempt to estimate crop losses due to insect each plot were counted 45 D A E . At harvest, the attack. These include visual damage scores, compar- number of harvestable panicles were recorded, sun ing yield f r o m fields having different levels of natural dried and threshed, and grain mass was recorded. infestation, comparing yield of individual plants F r o m each plot, 50-100 stems were split open and w i t h and w i t h o u t infestation, and comparing yield of stem tunneling was recorded. chemically protected and nonprotected plots. Anoth- er method involves releasing insects in varying Artificial infestation. Stem borer infestation on number per plant or plot and correlating d a m - sorghum is very low d u r i n g the rainy season at age/yield w i t h insect density. This method has also ICRISAT Center. Uniform infestation is obtained been used in c o m p a r i n g yield of resistant and sus- by using eggs or first-instar larvae reared on artificial ceptible varieties under insect infestations (Walker diet (Taneja and Leuschner 1985). For larval infesta- 1983). T w o studies on yield loss estimation are t i o n , a split-split plot design was used in b o t h years reported in this paper. The first involves the spotted w i t h genotypes I C S V 1 and PS 28157-1 planted in stem borer, C. partellus in sorghum at I C R I S A T the m a i n plots. Subplots w i t h i n the main plots were Center in India, and the second is on the millet stem infested at 15,20,30,40, and 50 D A E . W i t h i n these borer, C. ignefusalis in pearl millet at the ICRISAT subplots, insect density was varied in subplots. Sahelian Center in Niger. Insect density per plant was tested at 0,4,8,12 in 1985, and 0,1,2,4,8,12 in 1986. Each sub-subplot consisted of 3 rows of 4 m length. A l l plants in the M a t e r i a l s a n d M e t h o d s central rows were infested w i t h a specified number of first-instar larvae. A selected number of larvae S o r g h u m (noted above for each year) were gently mixed w i t h a carrier (poppy seeds) and introduced in the leaf Yield loss in sorghum due to stem borer (C. partel- w h o r l to initiate infestation. lus) attack was estimated by t w o methods: protect- For egg infestation, a split-plot design was used in ing the crop f r o m stem borer infestation at different 1985 w i t h genotype I C S V 1 and infestation stages of g r o w t h stages by insecticide application ( C a r b o f u - 15,20,30,40, and 50 D A E were established as main ran 3G) in the leaf w h o r l ; and infesting the crop w i t h plots. Insect density of 0,10,20,33 and 50% plants eggs and larvae at different g r o w t h stages. The first infested w i t h single egg masses were established as experiment was conducted under natural borer subplots. In 1986, a split-split plot design was used

9 6 Table 1. Effect of protection levels on stem borer infestation, grain yield, and avoidable losses in sorghum, Hisar, rainy seasons 1982-83.

1982 1983

Dead hearts Grain yield A v o i d a b l e Dead hearts Grain yield A v o i d a b l e 1 1 -1 Treatment (%) (t ha- ) loss (%) (%) (t ha ) loss (%)

Protection between 15-60 D A E 2 10.5 3.70 0.0 9.5 2.33 0.0 15-45 D A E 8.2 3.40 8.1 12.4 2.00 14.2 15-30 D A E 20.3 2.93 20.8 21.8 1.74 25.3 Z e r o p r o t e c t i o n 62.2 1.08 70.8 60.1 1.01 56.6

SE ±2.98 ± 0.126 ±3.79 ±0.147

C V (%) 17 8 23 17

Y i e l d i n intensive Y i e l d in a p a r t i c u l a r p r o t e c t e d p l o t t r e a t m e n t 1. A v o i d a b l e loss (%) = x 100 Y i e l d i n intensive p r o t e c t e d p l o t 2 . D A E d e n o t e days after c r o p emergence.

w i t h genotypes l C S V 1 and PS 28157-1 as the m a i n 5m). Observations on borer infestation were re- plots, infestation stages as subplots and insect den- corded at 35 days after sowing ( D A S ) , 50 D A S , and sity as sub-subplots. Plot size was 8 rows of 4 m at harvest. length and the central 4 rows were infested w i t h a specified number of egg masses. Each egg mass, Insecticide trial. Quantitative estimates of yield containing 50-60 eggs was stapled at the top f o u r t h loss in millet were determined in 1985 by using leaf. paired comparisons of insecticide-protected and Observations on leaf damage were recorded one nonprotected plots. Two varieties, Nigeria Compo- week after infestation. T o t a l number of plants and site and a local cultivar, were sown in a randomized those showing deadhearts were recorded three weeks split plot design in six replications with varieties as after infestation. At harvest, harvestable panicles on m a i n treatments and insecticide a p p l i c a t i o n of -1 m a i n stems and tillers were counted in the infested Rogor® (dimethoate, 500g a.i. ha ) as subtreat- rows. These panicles were dried and threshed, and ments. The first insecticide treatment was applied at grain mass was recorded. Stem tunneling was also 15 D A S and subsequently at two-week intervals for recorded at harvest by splitting open 50 stems f r o m a total of four applications. Observations on borer each plot. infestation were recorded at 35 and 50 D A S , and at harvest f r o m an effective area of 5m x 5m w i t h i n subplots of 8m * 8m. G r a i n yield f r o m harvested pan- Pearl Millet icles was recorded after sun-drying and threshing.

Date of sowing trial. The relationship between crop age, date of sowing and extent of crop damage Results and Discussion by C. ignefusalis in pearl millet was investigated in field trials at the National A g r i c u l t u r a l Research S o r g h u m Station, Kamboinse, B u r k i n a Faso, in 1981 and 1982, and at the I C R l S A T Sahelian Center, Sadore, Natural infestation. D u r i n g 1982 and 1983, when Niger in 1984 and 1985. Three varieties were used in only genotype C S H 1 was used, stem borer infesta- each trial: Nigeria Composite, Ex-Bornu, and a local t i o n in c o n t r o l plots (no protection treatment) was cultivar at Kamboinse; and H K B t i f , C I V T , and a 60 and 6 2 % (Table 1). G r a i n yield in fully protected -1 -1 local cultivar at Sadore. F o u r replications of a ran- treatments was 3.7 t ha in 1982 and 2.33 t ha in domized split- plot design were set up w i t h sowing 1983. Avoidable loss, calculated on the basis of grain dates as m a i n plots and cultivars as subplots (5m x yield obtained t h r o u g h intensive protection and no

9 7 Table 2. Effect of protection levels on stem borer infestation, grain yield, and avoidable losses in sorghum, Hisar, rainy season 1984.

C S H 1 I C S V 1 IS 2205

D e a d - G r a i n A v o i d a b l e D e a d - G r a i n A v o i d a b l e D e a d - G r a i n A v o i d a b l e heart yield loss1 heart yield loss heart yield loss 1 -1 1 Treatment <%) (t ha- ) (%) (%) (t ha ) (%) (%) (t ha- ) (%)

Protection between 15-60 D A E 2 25.2 5.17 0.0 28.0 4.24 0.0 33.9 1.87 0.0 15-45 D A E 23.8 4.39 15.1 49.0 2.64 37.7 37.6 1.28 31.6 15-30 D A E 39.2 4.79 7.4 50.2 2.62 38.2 30.6 1.91 0.0 30-60 D A E 61.1 3.11 39.8 75.9 0.76 82.1 43.2 1.18 36.9 30-45 D A E 53.7 3.70 28.2 79.0 0.74 82.5 43.0 1.04 44.4 45-60 D A E 95.1 1.60 69.1 100.0 0.33 92.2 47.6 0.90 51.9 Z e r o Protection 100.0 0.19 96.3 100.0 0.00 100.0 55.5 0.75 59.9

SE ± 3.46 ± 0.259 ±3.46 ± 0.259 ± 3.46 ± 0.259

C V (%) 18 26 18 26 18 26

Y i e l d i n intensive Yield in a particular protected plot t r e a t m e n t 1. A v o i d a b l e loss (%) x100 Yield in intensive protected plot 2 . D A E denotes days a f t e r emergence.

protection, ranged between 56.6 and 70.8% in two corresponding grain yields were noticed in all three years. M a x i m u m grain yield was obtained when the genotypes tested (Table 2). In susceptible genotypes c r o p was protected between 15 and 60 D A E , h o w - C S H 1 and 1CSV 1, 100% infestation was observed ever, m a x i m u m differences in yield levels were and negligible grain yield was realized in zero- recorded between zero protection and early stages of protection treatment. In resistant genotype IS 2205, protection (15-30 D A E ) . however, m a x i m u m infestation was 55.5% and some In 1984, w i t h increase in protection level treat- grain yield was obtained (0.75 t ha-1). A l t h o u g h ments, different levels of stem borer infestation and under protected conditions, CSH 1 and ICSV 1

Table 3. Effect of protection levels on stem borer infestation, grain yield, and avoidable losses in sorghum, Hisar, rainy season 1985.

l C S V 1 PS 28157-1

Dead hearts Grain yield A v o i d a b l e Dead hearts G r a i n yield A v o i d a b l e 1 1 -1 Treatment (%) (t ha- ) loss (%) (%) (t ha ) loss (%)

P r o t e c t i o n between 15-60 D A E2 15.9 3.57 0.0 6.4 4.45 0.0 15-45 D A E 8.1 2.32 35.0 4.1 3.26 26.7 15-30 D A E 19.5 2.68 24.9 6.7 3.35 24.7 30-60 D A E 36.5 0.72 79.8 14.7 1.68 62.2 30-45 D A E 36.6 0.84 76.5 16.7 1.21 72.8 Z e r o p r o t e c t i o n 80.3 0.01 99.7 45.7 0.73 83.6

SE ±4.66 ±0.667 ±4.66 ±0.667

C V (%) 26 16 26 16

Y i e l d i n intensive Yield in a particular p r o t e c t e d p l o t t r e a t m e n t 1. A v o i d a b l e loss (%) = x 100 Yield in intensive protected plot 2 . D A E denotes days a f t e r emergence.

9 8 yielded significantly higher than the resistant geno- hearts) and grain yield w i t h various borer densities, type; under zero protection IS 2205 outyielded both at different stages of infestation during 1985, are susceptible genotypes. M a x i m u m infestation and presented in Figure 1. Infestation at 15 D A E resulted grain yield differences were obtained between zero- in m a x i m u m damage and subsequent yield reduc- protected and early protected (15-30 D A E ) treat- t i o n in b o t h resistant PS 28157-1 and susceptible ments, w h i c h were similar to the 1982-83 results. ICSV 1 genotypes. At this stage of infestation, there In 1985, 8 0 % deadhearts were recorded on sus- was no significant difference between various borer ceptible I C S V 1 compared w i t h 45.7% on resistant densities (4,8, and 12 larvae plant-1) in terms of PS 28157-1 in zero-protected treatments (Table 3). damage and grain yield for either genotype. How- Here again, in zero-protected treatment, there was ever, infestations at 20 DAE showed linear increase no grain yield in the susceptible genotype, while in borer damage and decrease in grain yield, as insect some yield was obtained f r o m the resistant genotype density increased. In resistant genotypes, infestation even under no protection. Minimum avoidable was lower at all borer densities and corresponding losses were observed when the crop was protected grain yields were higher than in the susceptible geno- between 15 and 30 D A E . type. Infestations carried out 30 D A E , and later, d i d F o u r years of data on the effect of protection not result in deadheart f o r m a t i o n ; however, grain levels indicates that the m a x i m u m c o n t r o l of stem yield decreased in infested plots at 30 D A E . At 40 borer, and subsequently higher grain yield was D A E infestation, there was no decrease in grain obtained when the crop was protected between 15 yield. and 30 D A E . This is the crop stage at w h i c h borer In 1986, similar infestations and grain yield reduc- infestation results in deadheart formation, which is tions resulted when 4,8, and 12 larvae were i n t r o - the p r i m a r y damage s y m p t o m related w i t h grain duced per plant. However, w i t h the inclusion of t w o yield reduction (Taneja and Leuschner 1985). There more infestation levels (1 and 2 larvae per plant), was no trend observed in stem tunneling as a some trend was observed even at 15 D A E infesta- parameter influencing yield within different protec- tions (Fig. 2). Deadheart expression decreased as the t i o n levels in any of the genotypes tested d u r i n g infestation was delayed. Avoidable losses increased 1983-85. w i t h the increase in borer density and decreased as the infestation was delayed (Table 4). Also, avoid- Artificial infestation. Stem borer infestation (dead- able losses were lower in resistant genotypes than in

Table 4. Estimation of avoidable losses due to stem borer infestation in sorghum, ICRISAT Center, rainy season 1986.

A v o i d a b l e loss (%)1

I C S V 1 PS 28157-1

Insect density 1 5 D A E2 2 0 D A E 30 D A E 15 D A E 20 D A E 30 D A E

Larval infestation (Larvae plant -1)

1 31.7 28.0 25.2 13.1 15.9 3.0 2 48.0 38.4 41.1 29.3 28.1 9.8 4 70.2 41.2 43.0 45.9 31.1 9.8 8 86.5 54.4 55.6 79.9 50.5 24.8 12 84.9 56.8 58.9 86.1 48.3 28.6

Egg infestation (% plants with eggs)

10 23.4 21.3 15.3 22.0 5.5 2.2 20 52.3 37.8 25.9 41.4 20.9 14.9 33 69.3 53.0 32.2 48.9 22.8 22.4 50 61.5 59.1 51.4 57.3 39.0 36.8

Y i e l d in intensive Y i e l d in a p a r t i c u l a r p r o t e c t e d p l o t - t r e a t m e n t 1. A v o i d a b l e loss (%) = x 100 Yield in intensive protected plot 2 . D A E denotes days after emergence.

9 9 the susceptible genotypes in almost all treatments. ingly decreased the grain yield. Resistant genotypes W i t h egg infestation, borer damage was less than showed less borer damage and higher grain yield in that incurred w i t h larval infestation. Even w i t h 5 0 % all the treatment levels. W i t h egg infestation, as in plants infested w i t h egg masses 15 D A E , the m a x i - larval infestation, borer damage decreased as the m u m damage was 6 8 % deadhearts in I C S V 1 and infestation was delayed. Similarity, avoidable losses 5 9 % in PS 28157-1 ( F i g . 3). There was a linear rela- increased as borer density increased, and decreased tionship between damage and borer density: increase as infestation was delayed (Table 4). in borer density increased damage, and correspond- Data from natural and artificial infestation indi-

I C S V 1 (% of deadhearts) PS 28157-1 (% of deadhearts) ICSV 1 (Yield) PS 28157-1 (Yield)

15 D A E 2 0 D A E 100 4 100 4 9 0 9 0

8 0 8 0 3 3 7 0 7 0

6 0 6 0

5 0 2 5 0 2

4 0 4 0

3 0 3 0 1 1 2 0 2 0

10 10

0 0 0 0 0 4 8 12 0 4 8 12 B o r e r d e n s i t y ( l a r v a e p l a n t-1 ) B o r e r d e n s i t y ( l a r v a e p l a n t " ' )

4 100 100 4 3 0 D A E 4 0 D A E 9 0 9 0

8 0 8 0 3 3 7 0 7 0

6 0 6 0

5 0 2 5 0 2

4 0 4 0

3 0 3 0 1 1 2 0 2 0

10 10

0 0 0 0 0 4 8 12 0 4 8 12 B o r e r d e n s i t y ( l a r v a e p l a n t-1 ) Borer density (larvae plant-1)

F i g u r e 1 . R e l a t i o n s h i p b e t w e e n s t e m b o r e r d e n s i t y , i n f e s tation, and yield under artificial infestation, I C R I S A T C e n t e r , r a i n y s e a s o n 1 9 8 5 .

100 ICSV 1 (% of deadhearts) PS 28157-1 (% of deadhearts) ICSV 1 (Yield) PS 28157-1 (Yield) 100 3.5 15 D A E 3 . 0 8 0 2.5

6 0 2 . 0

1.5 4 0 1.0

2 0 0.5

0 0 . 0

0 2 4 6 8 10 12 Borer density (larvae plant-1)

100 3.5 20 D A E 3.0 8 0 2.5 6 0 2 . 0

1.5 4 0

1.0 2 0 0.5

0 0 . 0

0 2 4 6 8 10 12 Borer density (larvae plant-1)

100 3.5

3.0 8 0 30 D A E 2.5

6 0 2 . 0

4 0 1.5

1.0 2 0 0 . 5

0 0 . 0 0 2 4 6 8 10 12 Borer density (larvae plant-1)

Figure 2. Relationship between stem borer density, in festation, and grain yield under artificial infestat i o n using larvae, ICRISAT Center, rainy season 1986.

1 0 1 ICSV 1 (% of deadhearts) PS 28157-1 (% of deadhearts) ICSV 1 (Yield) 1 0 0 PS 28157-1 (Yield) 3 . 0 15 D A E

8 0 2 . 5

2 . 0 6 0

1.5 4 0 1.0

2 0 0.5

0 0 . 0

0 10 2 0 3 0 4 0 5 0 B o r e r d e n s i t y ( p e r c e n t a g e o f p l a n t s w i t h e g g m a s s )

100 3 . 0 20 D A E 2.5 8 0

2 . 0 6 0

1.5

4 0 1.0

2 0 0.5

0 0 . 0

0 10 2 0 3 0 4 0 5 0 B o r e r d e n s i t y ( p e r c e n t a g e o f p l a n t s w i t h e g g m a s s )

100 3 . 0

30 D A E 2.5 8 0

2 . 0 6 0 1.5

4 0 1.0

2 0 0 . 5

0 0 . 0 0 10 2 0 3 0 4 0 5 0 B o r e r d e n s i t y ( p e r c e n t a g e o f p l a n t s w i t h e g g m a s s )

Figure 3. Relationship between stem borer density, in festation, and grain yield under artificial infesta t i o n using egg masses, ICRISAT Center, rainy season 1986.

1 0 2 cates that early infestation by stem borer is crucial, crop damage w i t h i n varieties f o r the insecticide p r o - results in deadheart f o r m a t i o n , and causes grain tected and nonprotected treatments (Table 5). How- yield reduction. This has also been observed by ever, between varieties, Nigeria Composite was Singh et al. 1968, and Taneja and Leuschner 1985. infested m o r e than the local cultivar. It was also observed that low levels of borer infestation resulted in a slight yield increase of the nonprotected treat- Pearl Millet ment over the control (Nigeria Composite 11.9%, Sadore local 1.3%). Similar results were obtained Date of sowing trial. Initial crop damage caused earlier by Harris (1962), although in a separate by Coniesta infestation is usually observed as dead- experiment w i t h high levels of borer attack he hearts of seedlings, attributed to feeding activities of recorded a grain yield loss of 15%. y o u n g larvae of the first generation (Harris 1962). Leaf feeding symptoms have not been recorded in this species. Conclusions At Kamboinse and Sadore, there were no significant differences between varieties in deadheart for- In sorghum, m a x i m u m c o n t r o l of stem borer infes- m a t i o n but differences were observed between sow- tation was obtained when the crop was protected ing dates, w i t h the late crop showing a higher between 15 and 30 D A E by the application of car- p r o p o r t i o n of deadhearts than the early crop. At b o f u r a n granules in the leaf whorls. This protection b o t h locations, stem damage increased w i t h a delay also afforded significantly higher grain yields. Under in sowing. artificial infestation, resistant genotypes showed a Tiller infestation and internode damage were consistent advantage in avoiding grain yield loss. m u c h higher on the t h i r d - s o w n crop (mean of 84.3 Infestations at 15 D A E resulted in m a x i m u m d a m - and 44.3% at Kamboinse; 84.7 and 40.8% at Sadore) age and subsequent yield reductions in all genotypes than on the first crop (mean of 64.8 and 2.6% at tested. Data from both natural and artificial infesta- K a m b o i n s e , 26.5 and 1.5% at Sadore). G r a i n yield t i o n indicates that early infestation by stem borer is data were confounded by bird damage but data col- the most damaging and results in greatest reduction lected on tiller productivity also indicated a corres- of yield. p o n d i n g increase in nonproductive tillers w i t h a W i t h pearl millet, trials in B u r k i n a Faso and Niger delay in sowing. have shown that early sowing results in greater tiller p r o d u c t i v i t y and higher yields. Trials w i t h insecti- Insecticide trial. A l t h o u g h planted in mid-June cide control proved inconclusive in estimating yield 1985, this trial experienced a low level of borer infes- loss in millet. A d d i t i o n a l w o r k in this area might be tation. No significant differences were observed in useful.

Table 5. Assessment of crop loss caused by infestation of Coniesta ignefusalis in two millet cultivars, Sadore, Niger 1985.

Cultivar/treatment

Nigeria Composite Sadore Local

Protected Non- Protected Non- Parameters measured c o n t r o l protected c o n t r o l protected M e a n ± SE

N o . o f larvae/stem (50 D A S 1 ) 1.5 3.0 0.0 0.2 1.2 ± 0.72 Infested stems (%) (50 D A S ) 8.3 10.0 1.7 3.3 5.8 ± 2.10 Internodes tunneled (%) (50 DAE2 ) 1.4 2.6 0.3 0.6 1.2 ± 0.60 N o . o f larvae/stem (at harvest) 11.5 11.2 6.3 7.5 9.1 ± 1.49 Infested stems (%) (at harvest) 28.0 37.3 17.3 23.0 26.4 ± 2.87 Internodes tunneled (%) (at harvest) 4.9 8.5 2.6 3.4 4.8 ± 0.52 G r a i n yield ( k g ha-1) 1856 2076 1414 1432 1720 ± 372 Yield loss (%) 11.93 1.3

1 . D A S denotes days a f t e r s o w i n g . 2 . D A E denotes days a f t e r emergence. 3 . Indicates y i e l d a d v a n t a g e o f n o n p r o t e c t e d over p r o t e c t e d c o n t r o l .

103 R e f e r e n c e s

F A O . 1980. Elements of integrated control of sorghum pests. F A O Plant P r o d u c t i o n and P r o t e c t i o n Paper n o . 19. R o m e Italy: F A O . 159 pp.

Harris, K . M . 1962. Lepidopterous stem borers of cereals in Nigeria. Bulletin of Entomological Research 53:139-171.

Singh, S.R., Vedamoorthy, G., Thobbi, V.V., Jotwani, M.G., Young, W.R., Balan, J.S., Srivastava, K.P., Sandhu, G.S., and Krishnananda, N. 1968. Resistance to stem borer, Chilo zonellus (Swinhoe) and stem f l y , Athe- rigona varia soccata Rond. in world sorghum collection in I n d i a . M e m o i r s o f the E n t o m o l o g i c a l Society o f I n d i a 7:1-79.

Walker, P.T. 1983. The assessment of crop losses in cereals. Insect Science a n d its A p p l i c a t i o n 4(1-2):97-104.

Young, W . R . 1970. S o r g h u m insects. Pages 235-287 in S o r g h u m p r o d u c t i o n and u t i l i z a t i o n ( W a l l , J.S., and Ross, W.M., eds.). Westport, Connecticut, USA: AVI Publish- ing C o .

104 Management Options for Sorghum Stem Borers for Farmers in the Semi-Arid Tropics

K.F. Nwanze1 and R.A.E. Mueller2

Abstract

Currently recommended control measures against sorghum stem borers are briefly reviewed. Generally, successful methods applied in developed countries have been tested at research stations in developing countries and recommended to farmers in the semi-arid tropics. The extent of their use by farmers is assessed and farm-and sector-level constraints to adaptation are evaluated. Past research leading to control recommendations did not adequately take local farming practices into account. An approach for farmer-oriented research on control methods is suggested.

Specific research has not been conducted on the Introduction adoption by farmers of stem borer management recommendations. Prerequisites to the success of Literature abounds w i t h i n f o r m a t i o n on the control any pest-control technology, and thus the success of of sorghum pests, and m u c h of it deals w i t h stem any stem borer management research program have borers. Recommendations for stem borer manage• been identified by Reichelderfer and Bottrell (1985, ment range f r o m the simple cultural practice of sow• p.284): "Basically any pest-control technology must ing date, to chemical and biological c o n t r o l , modern meet four criteria before it can be considered a likely resistant genotypes, and more ambitious integrated candidate for acceptance and overall effectiveness: it pest management. However, very few farmers of the must be politically practical, socially acceptable, and semi-arid tropics ( S A T ) practice these recommenda• economically feasible, as well as technically effec- tions, which gather dust in libraries. t i v e . "

1. Principal Cereals Entomologist, Sorghum Group, Cereals Program, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Andhra Pradesh 502 324, India. 2. Principal Economist, Economics Group, Resource Management Program, at the same location.

I C R I S A T Conference Paper no. CP 492. l C R I S A T (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, ICRISAT Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

105 T r a d i t i o n a l research concentrates on the technical 1987). S o r g h u m stalks are also used f o r fencing, and effectiveness of pest management recommendations, provide bedding f o r livestock. usually neglecting or ignoring other criteria vital for The severity of damage to s o r g h u m by stem borers success. This emphasis on technical feasibility often varies considerably across regions of the S A T . results in pest control recommendations that can, at Harris (1985) estimated overall losses to be on the best, be adopted only by progressive farmers. P r o - order of 5 - 1 0 % in many sorghum-growing areas of gressive researchers should, ideally, take all four West A f r i c a , especially where early attack causes criteria into account so that their recommendations loss of stand. A v o i d a b l e grain losses on the h y b r i d can be adopted by traditional farmers in the S A T . s o r g h u m C S H 1 and the variety Swarna were esti- In this paper we explore some implications of mated to be about 5 5 - 8 3 % in I n d i a ( J o t w a n i et al. adopting a f a r m i n g systems perspective in stem 1971, J o t w a n i 1972). In a survey of cereal losses in borer management research in an attempt to increase Kenya and Tanzania, Walker (1967) reported losses the u t i l i t y of the research o u t p u t f o r farmers. The in yield of sorghum due to stem borer damage rang- essence of this approach is that by spending more ing f r o m 18-27%. A recent survey of farmers' per- effort on anticipating the consequences of manage- ception of losses due to stem borer in western Kenya ment practices that are i m p o r t a n t f o r farmers, we reported a range of 15-40% (Seshu Reddy In press). reduce the chance of recommending pest manage- M o s t losses in yield are attributed to early attack on ment practices that are not adopted by farmers. the growing plant. Correlations of counts of stem damage, w i t h yield at or before harvest, have often failed to demonstrate any reduction in grain yield (Harris 1962, I C R I S A T 1987). I m p o r t a n c e o f S o r g h u m a n d S o r g h u m S t e m B o r e r s

F A O (1986) reports sorghum p r o d u c t i o n f r o m 89 R e v i e w o f R e c o m m e n d a t i o n s f o r countries, 33 of w h i c h are developing countries in S t e m B o r e r M a n a g e m e n t the S A T . These countries contribute about 5 0 % of the annual w o r l d sorghum grain p r o d u c t i o n of 80 Pest management strategies that have been sug- m i l l i o n tonnes, and account f o r 7 5 % of the 50 m i l • gested f o r sorghum stem borers in the S A T (cultural, lion hectare planted w i t h sorghum, worldwide. chemical, and biological control, host-plant resis- In contrast to the s o r g h u m - g r o w i n g countries in tance, and integrated pest management) are briefly L a t i n A m e r i c a where sorghum grain is used as reviewed in this section. The more exotic control animal feed, nearly 9 0 % of s o r g h u m produced in methods such as the use of pheromones, juvenile developing countries of the S A T of Asia and A f r i c a hormones, and chemosterilants are excluded. is used f o r f o o d ( F A O 1984). S o r g h u m grain is a staple diet of many subsistence farmers and rural laborers in the S A T , and is an i m p o r t a n t source of Cropping Practices calories and protein. F o r example, p o o r rural f a m i - lies in I n d i a on average derive 15% of their daily C r o p p i n g practices can be conceived as having calories and 16% of their daily protein f r o m sorghum evolved over l o n g periods of time and being well- ( M u r t y and v o n O p p e n 1985). Detailed surveys in adapted to local environments. Changes in cropping I n d i a ( R y a n et al. 1984) showed that sorghum con- practices can have i m p o r t a n t impacts on stem borer tributes about 2/3 of daily protein and calories con- ecology that may be exploited in pest management. s u m p t i o n by rural people in sorghum g r o w i n g tracts. Such changes may, however, have intricate agro- S o r g h u m grain is also widely used in the production nomic and economic side effects that are difficult to of indigenous beer in A f r i c a (Haggblade 1987). The anticipate and that diminish the acceptance of uses of s o r g h u m are not confined to grain. S o r g h u m recommended cropping practices by farmers. stalks, f o r example, became increasingly valuable in parts of I n d i a in periods of d r o u g h t f r o m 1980 to 1986. D u r i n g that time the price of sorghum fodder Rotations rose by about 270%. Fodder's share in the value of sorghum p r o d u c t i o n has increased in the same Rotations can check stem borer population build-up period f r o m below 5 0 % t o more than 7 0 % ( W a l k e r by r e m o v i n g p r i m a r y hosts of the pest f o r extended

106 periods. Rotations including fallow, however, have alone will result in higher sustainable sorghum vanished i n parts o f the S A T w i t h explosive p o p u l a - yields. t i o n g r o w t h , increasing land pressure, and declining land productivity ( M a t l o n and Spencer 1984). F u r - Farm Sanitation t h e r m o r e , the arrival or absence of rains, sudden changes in price ratios, and other variables outside Several stem borer species will carryover in sorghum the c o n t r o l of farmers often impede the planned stems (C. partellus, B. fusca, A. igncfusalis) or sur- succession of crops. F o r example, analysis of the vive the d r y season on alternate w i l d grass hosts crop choices of a small sample of farmers in India (Sesamia spp). Collecting and b u r n i n g stubble and showed that about half of all attempted rotations are stalks, or p l o w i n g and destroying crop residue are interrupted ( I C R I S A T 1987). recommended practices (Bowden 1956, Nye 1960, and Harris 1962). Adesiyun and Ajayi (1980) found in northern Nigeria that partial b u r n i n g of stalks Intercropping killed 9 5 % of diapausing B. fusca larvae, and cured the stalks, i m p r o v i n g their quality f o r housing and M o s t farmers i n the S A T g r o w sorghum i n crop fencing material. Species that survive on d r y season mixtures, usually w i t h legumes and sometimes w i t h w i l d graminaceous hosts are effectively controlled other cereals. In general, crop mixtures reduce pest by crop removal. In the densely populated S A T incidence when the choice of the crops in the m i x t u r e areas of I n d i a , field sanitation can hardly be im- is properly done. However, the individual c o m p o - proved. Here all plant residue is either grazed or nent crops may not equally benefit. F o r example, in collected by the abundant f a r m labor. In Africa, K e n y a , O g w a r o (1983) f o u n d increased borer levels where f a r m labor is scarce and draft animals are not in maize when intercropped w i t h sorghum, while typically used, postharvest plowing is very costly. b o r e r levels remained the same in s o r g h u m . S o r g h u m stalks used as fencing material may have A m o a k o - A t t a and O m a l o (1983) f o u n d that a no cheap substitutes in remote r u r a l areas or may be s o r g h u m / m a i z e intercrop was more favorable to too valuable as fodder to be burned. C. partellus attack than an intercrop of sorghum and cowpea. Similar studies by Mahadevan and Chelliah (1986) in I n d i a showed a m u c h higher incidence of Manuring borer attack and lower yield in m o n o c r o p sorghum compared to sorghum intercropped w i t h lablab F a r m manure provides nutrients, improves soil (Lablab purpureus (L.) Sweet). A l t h o u g h there is structure, and increases soil water-holding capacity, scientific evidence of an effect of the composition of w h i c h in t u r n improves plant vigor and g r o w t h . sorghum intercrops on stem borer ecology, there are Vigorously g r o w i n g sorghum suffers less borer d a m - no studies showing that farmers grow specific sor- age and escapes deadheart f o r m a t i o n . A l t h o u g h g h u m intercrops to exploit this effect. livestock numbers are increasing at a slow pace in the S A T of I n d i a , the ratio of livestock per cropped area is stagnating, l i m i t i n g the scope for increasing Sowing Date application of manure. Furthermore, where fire- w o o d is scarce, dung is also used f o r fuel. F a r m i n g In the sorghum tracts of the S A T , sowing of households in I n d i a b u r n about 1 t of dried d u n g per sorghum is determined by rainfall. Planting after the year (ICRISAT 1986). These factors cause farmers first rains is the first step the farmer takes to ensure a to apply manure less frequently and in lesser q u a n t i - good crop. This practice has considerable relevance ties than they w o u l d if more manure was available. to stem borers since the early sown crop usually Local sorghum cultivars in I n d i a rarely receive suffers less borer attack than a crop sown later manure. W a l k e r and R a o (1982) f o u n d that only ( H a r r i s 1962, Nwanze 1981). Deviations f r o m this 1.4% of the plots planted w i t h postrainy season local rule are usually founded on other constraints that sorghum in two villages of Maharashtra, India, farmers have to consider, such as soil type and t o p o - received manure. In contrast, 60% of the high- graphy of plots ( M a t l o n 1980), labor bottlenecks, or yielding varieties ( H Y V ) sorghum plots in another risk of crop damage f r o m other insects. Given the village of the same state received inorganic fertilizer. many constraints affecting farmers' choice of sowing Farmers believe that sorghum is more responsive to dates, it is unlikely that a change m sowing dates inorganic fertilizer than to manure and reserve the

107 available manure f a r cash crops. Evidence f r o m 56 enemies is l i m i t e d by the short c r o p p i n g period and villages in 10 countries in sub-Saharan A f r i c a i n d i - the lack of continuous habitats for the natural ene- cates that m a n u r i n g fields is a practice that evolves mies. The introduction and establishment of Tri- w i t h increasing f a r m i n g intensity f r o m fallow to chogramma exiguem, a parasitoid on C. partellus annual cropping systems (Binswanger and Pingali eggs, represents a notable success in I n d i a ( J o t w a n i 1984). 1982). In A f r i c a , the overall rate of parasitism is l o w and only increases when borer damage is well advanced (Harris 1962, Nwanze 1985). Chemical Control

Several insecticides have been tested f o r the control Host-plant Resistance of stem borers. Their efficacy depends crucially on the t i m i n g o f application. I n A f r i c a , chemical c o n - At I C R I S A T Center, more than 70 germplasm sour- t r o l by c a r b o f u r a n , carbaryl, and endosulfan were ces and breeding lines have been identified as resis- f o u n d effective against B. fusca and Sesamia spp. tant to stem borer C. partellus. These materials are (Taneja and Leuschner 1985, Seshu Reddy and currently being used in I C R I S A T ' s breeding p r o - O m o l o 1985). Sharma (1985) listed nine insecticides grams. Sharma (1985) also listed 34 entries of which that are effective against C. partellus in I n d i a . G r a n - 25 were highly promising, having stable resistance ular f o r m u l a t i o n s of carbofuran applied directly and good agronomic characteristics. Several local i n t o the w h o r l gave reasonable c o n t r o l against cultivars and landraces exhibit a high tillering abil• C. partellus although the procedure is labor-intensive ity, and tillering, as an aspect of varietal tolerance at and was recommended only as a last resort (Teetes et low borer infestations, may result in an overall al. 1983). H i g h labor intensity w o u l d probably not increase in head p r o d u c t i o n ( H a r r i s 1962). Me ch a- prevent farmers in I n d i a to do this if stem borer were nisms of resistance and further studies on oviposi- a severe yield reducer. These insecticides are, how- t i o n behavior and crop physiology w i l l provide an ever, often unavailable in rural areas or too expen- adequate f o u n d a t i o n for the development of inte- sive f o r subsistence farmers. The assessment of grated pest management programs. At this time, chemical c o n t r o l of sorghum in the S A T by Davies however, stem borer resistant cultivars have yet to be (1982, p. 220) is as valid today as it was 6 years ago: released in the SAT. Furthermore, germplasm has " I n general, there is little convincing evidence of the not been screened f o r multiple resistance. We can- economic soundness of some of the recommenda- not, therefore, deny the possibility that cultivars tions made f o r insecticide use on sorghum, in devel- developed from stem borer resistant germplasm o p i n g countries, except in special high i n p u t , or at mi g h t break d o w n when exposed to multiple pest least high fertility ... situations". and disease pressure in farmers' fields. Chemical insect pest c o n t r o l on local cultivars of s o r g h u m is conspicuously absent in India. Evidence f r o m three study villages in different agroclimatic Integrated Pest Management (IPM) zones in S A T I n d i a (Binswanger and R y a n 1980) shows that only hybrid sorghum is sometimes treated The individual control methods discussed above w i t h insecticides in the event of shootfly or midge have their limitations and none is sufficient to ade- attack. We have no reports f r o m our village investi- quately c o n t r o l stem borer outbreaks. W h e n no sin- gators that farmers actually apply insecticides direct- gle c o n t r o l o p t i o n is sufficient, one may try to ly into the w h o r l . exploit the interactions of different control strategies integrated in a pest management system. I P M takes into account the interactions between biotic, Biological Control abiotic, and economic factors of crop p r o d u c t i o n , and pest management itself becomes part of manag- A number of natural enemies have been reported i n g or p r o d u c i n g a crop. T h e limitations of i n d i v i d - (Pradhan et al. 1971, F A O 1980, Seshu Reddy and ual c o n t r o l methods indicate that host-plant resis- Davies 1979, and Sharma 1985). In general, the effi- tance and cultural practices should be m a j o r c o m p o - ciency of natural enemies in particular f a r m i n g nents in the integrated management of sorghum environments is not k n o w n . The scope for success- stem borers. fully c o n t r o l l i n g sorghum stem borers w i t h natural Where integrated pest management has seriously

108 been t r i e d , its transfer to farmers often met w i t h in subject matter research on stem borers in the S A T constraints that were not anticipated by e n t o m o l o - is necessary. Transferring approaches to problem gists or social scientists. The m a i n deficiency of solving stem borer research from developed to many I P M recommendations is that they are t o o developing countries is perilous: it encourages cur- complicated to be explained by extension workers sory problem identification and acceptance of recom- and to be adopted by farmers. A d o p t i o n of thresh- mendations without critical appraisal. olds, a cornerstone of I P M , is an example. Carlson Problem-solving stem borer research has to con- and M u e l l e r (1987) f o u n d that a d o p t i o n of thresh- sider that practical problems are location-specific. olds by pigeonpea growers in S A T I n d i a was m u c h As mentioned earlier, estimates of yield losses from slower t h a n a d o p t i o n of ultra-low volume sprayers stem borer attack vary considerably across regions and that farmers w i t h little or no f o r m a l education and range f r o m 5-83%. Second, yield losses f r o m are very unlikely to be among the early adopters of stem-borer, as perceived by scientists, may be imper- thresholds. Drawing on her experiences of IPM field fect indicators of farmers' perceptions of the impor- w o r k in the developing countries, Goodell (1984, tance of stem-borer management. Third, solutions p. 18) characterized I P M as follows: of practical problems have to take into account the preferences, skills, resources, and constraints of the " O f the various components of m o d e r n agriculture, people whose problems are to be solved. We do not I P M presents by far the most difficult challenge to have to elaborate again here the contrast between t r a d i t i o n a l , small-scale farmers in the T h i r d W o r l d farmers and their environments in the S A T and in as they make the transition to scientific f a r m i n g . " the developed countries from where research approaches have been borrowed. These differences often prevent solutions from being successfully Assessment o f t h e R e c o m m e n d a t i o n s transferred f r o m developed to developing countries. In short, stem borer research has not been conducted Recommendations for stem-borer management, al- w i t h a f a r m i n g systems perspective. This defect most though appearing promising, have not carried far likely contributed to the dearth of stem borer m a n - beyond the research stations and libraries. F a r m agement recommendations that can be adopted by sanitation can either not be improved or only be farmers. i m p r o v e d at high cost. Sowing dates are confined by several constraints and are likely to be well-timed in t r a d i t i o n a l f a r m i n g systems that have evolved over long periods. Rotations are often obstructed by the S t e m B o r e r M a n a g e m e n t : A F a r m i n g vagaries of the weather in the S A T . M a n u r i n g local Systems Perspective cultivars of sorghum is unattractive to farmers. S o r g h u m cultivars that are acceptable to farmers Elements of Research Conducted and resistant or tolerant to stem borer and other yield reducers are yet to be released. There is no Over the last decade literature on f a r m i n g systems consistency in stem borer control through inter- research has burgeoned and the f a r m i n g systems cropping, and biological control is inefficient. Inte- approach has been recommended for research on grated stem borer management, finally, is likely to pest management technologies for small-scale farm- be severely constrained by the limited management ers (Altieri 1984). The essentials of farming systems capability of farmers. W h a t has prevented stem research are that it is conducted w i t h a f a r m i n g borer research f r o m c o n t r i b u t i n g more to sorghum systems perspective, that research begins and ends improvement? It was certainly not a lack of c o m - with the farmer (Plucknett et al. 1987). Several of the m i t m e n t on the part of researchers, nor were they objectives and methods employed in f a r m i n g sys- lacking in competence or devoid of a sense of tems research should be considered l o r introducing a urgency to solve the stem borer problem. M o r e f a r m i n g systems perspective into applied stem borer likely it was the contrary: highly motivated, compe- research. tent researchers attempted to achieve transferable The main objectives of research w i t h a f a r m i n g results quickly, often with frugal financial support, systems perspective that are relevant for stem borer by applying research approaches f r o m mentor insti- management research are: tutions in developed countries to the S A T . • to understand the physical, social, economic, and A p p l y i n g methods and principles of entomology human environment of agricultural production;

109 • to understand farmers' skills, constraints, prefer- in the S A T as it becomes available t h r o u g h research ences, and aspirations; reports. • to comprehend f a r m i n g systems; But the economic and political environment of • to identify possibilities f o r i m p r o v i n g existing sorghum production in the SAT also requires con- f a r m i n g systems; tinuous m o n i t o r i n g by researchers. This is particu- • to evaluate new or i m p r o v e d practices f o r possi- larly true in Africa, where some governments have ble testing on farms; and not yet attained levels of stability f o u n d in many • to test practices under n o r m a l f a r m conditions. Asian countries, and where agricultural research Research w i t h a f a r m i n g systems perspective pur- and extension systems often are less developed. We sues these objectives mainly w i t h three methods: (a) do not suggest that entomologists engage in detailed Base-data analysis f o r describing the f a r m i n g envi- surveys of the economic, political, and infrastructur- ronment in a region; (b) research station studies for al environment of agricultural p r o d u c t i o n , because the development of new components or the assembly m u c h of the necessary i n f o r m a t i o n is provided by of new f a r m i n g systems; and (c) o n - f a r m studies social scientists and by the local press. We do w h i c h involve o n - f a r m experimentation studies of recommend, however, that sorghum entomologists existing f a r m i n g systems, and studies of adoption consult social scientists and watch key price ratios and farm-household impacts of a new technology. that indicate changes in the economic environment. Some of the key indicators are the price ratios between the farm-gate sorghum price and r u r a l Objectives and Methods Applied to Stem labor wage rates, or the prices f o r other f o o d staples, Borer Research or the prices for insecticides.

In Table I we have correlated objectives and methods Farming System. An understanding of the f a r m - for stem borer management research conducted w i t h ing system, not just the c r o p p i n g system, is particu- a f a r m i n g systems perspective. In this section the larly i m p o r t a n t for stem borer researchers in the elements of Table 1 are discussed. S A T . There are many intricate linkages between the various production and consumption activities of Production Environment. In the past, stem borer small substistence or semi-subsistence farmers, and research has given adequate attention to the physical farmers may attribute little importance to stem bor- environment of sorghum p r o d u c t i o n . We expect ers as yield reducers. If stem borer management researchers w i l l also q u i c k l y absorb more detailed options are to be adopted by farmers they must fit i n f o r m a t i o n on the climatic and edaphic conditions into existing farming systems. Rarely are stem borer losses sufficiently high that farmers are likely to change their f a r m i n g system only to accommodate a Table 1. Objectives and methods of stem borer manage- stem borer management recommendations. ment research conducted with a farming systems perspective. Farmers. At the outset of any applied, p r o b l e m - M e t h o d s solving stem borer management research, entomologists should provide evidence on whether the insect ExperSiments is merely a pest or a pest p r o b l e m f o r farmers. This O n - O n - distinction between pests and pest problems is Objectives Surveys f a r m station Modeling important. Stem borers are regarded as pests because Environment ** they cause economic damage to sorghum. This is necessary but not a sufficient condition for stem F a r m i n g System ** ** borers to become a pest p r o b l e m f o r farmers. Sev- ** ** F a r m e r eral other conditions must also hold before stem i m p r o v e tech- * * * * borers can be regarded as a pest problem. n o l o g y First ot all, farmers must be able to associate the pest w i t h economic damage. This ability is likely to Evaluate new * * ** technology be conditioned by farmers' knowledge and skills, the degree of their exposure to farm management infor- ** ** Test new mation from extension services and other farmers, technology and the attention they give to sorghum.

110 Second, farmers may not regard stem borers as a risks. M e t h o d s f o r assessing the costs and returns of p r o b l e m pest when the perceived losses are small in pest management options are well established and relation to the perceived losses caused by other b i o - an excellent exposition was provided by Reichel- tic and abiotic yield reducers of sorghum, or where derfer et al. (1984). In many instances the required sorghum contributes little to the subsistence of the methods do not require an economist. f a r m families. Under such conditions, stem borers are unlikely to attract the scarce management atten- Improve Technology. Sometimes there may be an t i o n of farmers. opportunity for improving farmers' pest manage- T h i r d , stem borers are not a pest p r o b l e m unless ment practices with adaptive on-farm research. Sev- farmers have at their disposal means f o r reducing eral researchers have invested m u c h hope in this economic losses. W i t h o u t a feasible pest manage- approach (Matteson et al. 1984). From our expe- ment o p t i o n , farmers may regard stem borers as a rience in I n d i a , we are skeptical about this approach pest but not as a pest problem. because we have so far been unable to identify t r a d i - Establishing that stem borers are a pest problem tional methods used by farmers to manage sorghum f o r farmers requires that surveys of stem borer d a m - insect pests that have a potential for improvement age in farmers' fields are complemented by surveys through research (Rao and Mueller 1986). of farmers' perceptions of stem borers as a pest. Such surveys do not have to be large exercises i n v o l v i n g Evaluate New Technology. Evaluating new tech- entomologists, agronomists, and social scientists nologies in on-station experiments is the mainstay of equipped w i t h a detailed questionnaire. Often an traditional pest management research. Adoption of exploratory survey using rapid rural appraisal tech- a f a r m i n g systems perspective w o u l d not require niques may be sufficient to pesuade the researchers substantial changes in the experimental methods. It that stem borers are not a burning problem f o r would, however, require a broader set of criteria for farmers in whose fields entomologists have detected evaluating the results f r o m experiments, and appro- deadhearts and stem tunneling. Where more sub- priate selection of controls. Conventional research stantial evidence is required, a formal questionnaire uses classical statistical hypothesis testing to decide survey may be needed. Guidelines for f o r m a l percep- whether a new management technique performs in t i o n surveys can be obtained f r o m a pest perception some variable(s) better than a control technique w i t h n e t w o r k operating f r o m the Open University, U K some arbitrary level of significance. Such research (Tait 1981). Whether a recommendation is a solu- may be irrelevant f r o m a f a r m i n g systems perspec- t i o n for a farmer's stem-borer problem depends on tive. Classical statistical techniques are designed to the skills of the farmer and the farm's labor force, on rule out Type I errors, the error of rejecting the n ul l the costs of implementing the recommendation, and hypothesis when it is true, or the error of recom- on the expected returns f r o m stem-borer manage- mending a technology that is not superior to the ment. The adequacy of farmers' and laborers' skills control. The conventionally chosen probability of for implementing a recommended control practice c o m m i t t i n g this error bears no relation to the eco- can be assessed f r o m experiences w i t h similar practi- nomic consequences of this error. The f a r m i n g sys- ces but can be determined only in o n - f a r m trials. tems perspective could be introduced into the analy- Assessment of the costs of a stem-borer management sis of experiments with neo-classical statistical me- o p t i o n has to be based on the farm-gate prices of thods that take the costs of selecting a nonsuperior purchased inputs, and the value of the farm-owned technology into account (Manderscheid 1965, resources in their best alternative use at the time D i l l o n and Officer 1971). when they are needed for stem-borer control. The Technology evaluation, the evaluation of new cul- value to farmers of their owned resources may tivars in particular, is often conducted according to deviate considerably from average market prices, rigid rules defined by a large government research are usually location-specific, and may fluctuate con- administration. These rules are designed to select the siderably d u r i n g the cropping season. best technologies f o r a country, or for large agrocli- Assessment of the expected returns has to be matic zones, but may be too rigid for location- based on farmgate prices for sorghum at the time it is specific technologies that p e r f o r m very well in some sold. This assessment must take into account that locations, but poorly in the larger environments sorghum stems are a valuable c o m m o d i t y , and covered by these evaluation rules. should consider the effect of stem-borer manage- W i t h the rapidly falling costs of computer time, ment on the farmers' production and marketing modeling is becoming an increasingly attractive

111 opportunity for introducing a farming systems pers- the basic needs and objectives of a technology's pective i n t o the evaluation of new technologies recipient g r o u p is obviously an i m p o r t a n t step, but before they are actually tested on farms. However, one that is not always performed. Bypassing this step computer models usually have high set-up costs and w i l l p r o b a b l y lead to p o o r l y designed pest-manage- their use can be recommended only when the prospec- ment programmes." tive technology w i l l have many important and c o m - plex repercussions in the existing farming systems.

Testing N e w Technology. Once a promising new R e f e r e n c e s stem borer management o p t i o n has been identified in on-station experiments, it should be tested on a Adesiyun, A.A., and Ajayi, O. 1980. Control of the small n u m b e r of representative farms before it is s o r g h u m stem borer, Busseola fusca, by partial b u r n i n g of recommended to a large number of farmers. These the stalks. T r o p i c a l Pest M a n a g e m e n t 26:113-117. tests should be designed to evaluate the feasibility Altieri, M. A. 1984. Pest-management technologies f o r pea- and the performance of the new o p t i o n compared sants: a f a r m i n g systems a p p r o a c h . C r o p Protection with farmers' conventional techniques. These tests 3(1):87-94. also help to identify weaknesses or defects of the Amoako-Atta, B., and Omolo, E.O., 1983. Yield losses technique that may have gone unnoticed in o n - caused by the s t e m - / p o d - b o r e r c o m p l e x w i t h i n maize- station experiments. They provide feedback f r o m cowpea-sorghum intercropping systems in Kenya. Insect farmers that is essential f o r fine-tuning the recom- Science and its Application 4(1-2):39-46. me n d a t i o n . Binswanger, H.P.,and Ryan, J.G. 1980. Village-level stu- T h e most crucial test of any new technology is its dies as a locus for research and technology a d a p t a t i o n . a d o p t i o n by farmers. The recommendation of a new Pages 121-129 in Proceedings of the I n t e r n t i o n a l S y m p o - pest management technology should be followed by sium o n D e v e l o p m e n t and Transfer o f T e c h n o l o g y f o r a d o p t i o n studies that include adopters as well as Rainfed A g r i c u l t u r e and the S A T Fa rmer, 28 A u g - 1 Sep nonadopters. Such studies rely on surveys. They 1979, lCRlSAT Center, India. Patancheru, A.P. 502 324, allow researchers to document the success of their India: International Crops Research Institute for the S e m i - research, they provide i n f o r m a t i o n on the character- A r i d Tropics. istics of researchers' clients and their assessment of Binswanger, H.P., and Pingali, P.L. 1984. The e v o l u t i o n of the new methods. This i n f o r m a t i o n helps researchers f a r m i n g systems a n d agricultural technology in sub- to design the next generation of technology, and to Saharan A f r i c a . A g r i c u l t u r e and R u r a l D e v e l o p m e n t obtain funds f o r its development. Department Report no. ARU 23. Washington, D.C., USA: W o r l d Bank.

Bowden, J. 1956. New species of African stem-boring S u m m a r y a n d C o n c l u s i o n s Agrotidae (Lepidoptera). Bulletin of Entomological Research 47:415-428. In this paper we have briefly reviewed the practical- Carlson, G.A., and Mueller, R.A.E. 1987. Farmers' per- ity, and adoption, of stem-borer management recom- ceptions, education and a d o p t i o n of pest management mendations that have been reported in the literature. strategies by small farmers. Presented at the 11th Interna- This review indicated that most recommendations tional Congress of Plant Protection, 5-9 Oct 1987, Man i l a , are impractical and have not been adopted by Philippines. Patancheru, A.P. 502 324, India: Interna- farmers in the S A T . The i n t r o d u c t i o n of a f a r m i n g tional Crops Research Institute for the Semi-Arid Tropics. systems perspective to applied stem-borer manage- (Limited distribution.) ment research was suggested and some appropriate Davies, J . C . 1982. Pest losses and c o n t r o l of damage on objectives and research methods were discussed. s o r g h u m in developing countries the realities and the O u r expressed concern was f o r applied stem-borer m y t h s . Pages 215-223 in S o r g h u m in the eighties: proceed- research to take into account farmers' perception of ings of the International Symposium on Sorghum, 2-7 N o v the stem-borer pest problem and farmers' capacity 1981, ICRISAT Center, India. Vol.1. Patancheru, A.P. to implement recommended stem borer manage- 502 324, I n d i a : I n t e r n a t i o n a l Crops Research Institute for ment practices so that applied research results in the S e m i - A r i d Tropics. recommendations of practical use to S A T farmers. Dillon, J.L., and Officer, R.R. 1971. E c o n o m i c v. statisti- This n o t i o n has been aptly summarized by Reichel- cal significance in agricultural research and extension: a derfer and Bottrell (1985, p.286): " I d e n t i f i c a t i o n of pro-Bayesian view. Farm Economist 12(1):1-15.

112 F A O 1980. Elements of integrated control of sorghum M a t l o n , P.J. 1980. L o c a l varieties, p l a n t i n g strategies, a n d pests. F A O Plant P r o d u c t i o n a n d P r o t e c t i o n Paper n o . 19. early season f a r m i n g activities in t w o villages of central R o m e , Italy: F A O . 159 p p . Upper Volta. West African Economics Program Progress Report no.2. Ouagadougu, Upper Volta: International F A O 1984. F o o d balance sheets 1979-1981. R o m e , Italy: Crops Research Institute for the Semi-Arid Tropics. FAO. (Limited distribution.). F A O 1986.1985 F A O P r o d u c t i o n year b o o k vol.39. R o m e , M a t l o n , P.J., and Spencer, D . S . 1984. Increasing food Italy: F A O . production in sub-Saharan Africa: environmental prob- Goodell, G. 1984. Challenges to international pest manage- lems and inadequate technological solutions. American ment research and extension in the T h i r d W o r l d : do we Journal of Agricultural Economics 66(5):671-676. really w a n t I P M t o w o r k ? Bulletin o f the E n t o m o l o g i c a l Matteson, P.C, Altieri, M.A., and Gagne, W.C. 1984. Society of A m e r i c a 30(3): 18-27. M o d i f i c a t i o n of small farmer practices f o r better pest m a n - Haggbiade, S. 1987. Vertical considerations in choice-of- agement. Annual Review of Entomology 29:383-402. technique studies: evidence f r o m Africa's indigenous beer Murty, K.N.,and von Oppen, M. 1985. Nutrients d i s t r i b u - industry. Economic Development and Cultural Change tion and consumer preferences in India: some policy imp l i - 35(4):723-742. cations. Pages 179-200 in A g r i c u l t u r a l markets in the Harris, K . M . 1962. Lepidopterous stem borers of cereals in semi-arid tropics: proceedings of the International Wor k - Nigeria. Bulletin of E n t o m o l o g i c a l Research 53:139-171. shop, 24-28 Oct 1983, ICRISAT Center, India. Patan- cheru, A.P. 502 324, India: International Crops Research Harris, K . M . 1985. Lepidopterous stem borers of s o r g h u m . Institute for the Semi-Arid Tropics. Pages 161-167 in Proceedings of the International Sorghum Entomology Workshop, 15-21 Jul 1984, College Nwanze, K . F . 1981. Les borers des tiges des cereales en S t a t i o n , Texas, U S A . Patancheru, A . P . 502 324, I n d i a : Afrique de l'Quest Sahelienne: distribution, importance International Crops Research Institute for the Semi-Ari d relative et contiale. (In Fr.) Pages 109-145 in Proceedings, Tropics. L u t t e Biologique C o n t r e les Ravageus et ses Possibilities en A f r i q u e de l'Quest, 9-13 Feb 1981, D a k a r , Senegal. ICRISAT ( I n t e r n a t i o n a l C r o p s Research Institute f o r the W a s h i n g t o n , D.C., U.S.A: United States Agency f o r Inter- Semi-Arid Tropics). 1986. Annual report 1985. Patan- national Development. cheru, A . P . 502 324, I n d i a : I C R I S A T . Nwanze, K.F. 1985. S o r g h u m insect pests in West A f r i c a . ICRISAT ( I n t e r n a t i o n a l C r o p s Research Institute f o r the Pages 37-43 in Proceedings of the International Sorghum Semi-Arid Tropics). 1987. Annual report 1986. Patan- Entomology Workshop, 15-21 Jul 1984, College Station, cheru, A . P . 502 324, I n d i a : l C R l S A T . Texas, U S A . Patancheru, A . P . 502 324, I n d i a : Interna- Jotwani, M . G . , Chandra, D . , Young, W . R . , Sukhani, t i o n a l Crops Research Institute for the S e m i - A r i d T r o p i c s . T . R . , and Saxena, P . N . 1971. Estimation of avoidable Nye, I . W . B . 1960. The insect pests of graminaceous crops losses caused by insect c o m p l e x on s o r g h u m h y b r i d C S H - 1 in East A f r i c a . C o l o n i a l Research S t u d y n o . 3 1 . L o n d o n , and percentage increase in yield over treated c o n t r o l . U K : Her Majesty's Stationery Office. 48 pp. I n d i a n J o u r n a l o f E n t o m o l o g y 33:375-383. Ogwaro, K. 1983. Intensity levels of stem borers in maize Jotwani, M . G . 1972. Insect pests: m a j o r l i m i t a t i o n in p r o - and sorghum and the effect on yield under different inter- d u c i n g higher yields of s o r g h u m . Entomologists Newsletter cropping patterns. Insect Science and its Application 2:75. 4(1-2):33-37. Jotwani, M . G . 1982. Factors reducing s o r g h u m yields: Plucknett, D.L., Dillon, J.L., and Vallaeys, G.J. 1987. insect pests. Pages 251-255 in Sorghum in the eighties: Review of concepts in f a r m i n g systems research: the w h a t , proceedings of the International Symposium on Sorghum, w h y , and h o w . Pages 2 - 9 in Proceedings of the W o r k s h o p 2 - 7 N o v 1981, I C R I S A T Center, I n d i a . V o l . 1 . Patancheru, on F a r m i n g Systems Research, 17-21 Feb 1986, I C R I S A T , A . P . 502 324, India: I n t e r n a t i o n a l Crops Research Insti- Center, India. Patancheru, A . P . 502 324, I n d i a : Interna- tute f o r the S e m i - A r i d T r o p i c s . t i o n a l Crops Research Institute f o r the S e m i - A r i d T r o p i c s . Mahadevan, N . R . , and Chelliah, S. 1986. Influence of Pradhan, S. ed. 1971. Investigations on insect pests of i n t e r c r o p p i n g legumes w i t h s o r g h u m on the infestation of sorghum and millets final technical report 1965-70. New the stem borer, Chilo pariellus (Swinhoe) in T a m i l N a d u , Delhi, India: Indian Agricultural Research Institute. 157 India. Tropical Pest Management 32:162-163. p p . Manderscheid, L.V. 1965. Significance levels-0.05, 0.01, o r ? . A m e r i c a n J o u r n a l o f A g r i c u l t u r a l Economics 47(5): 1381-1385.

113 R a o , V . B . , and Mueller, R . A . E . 1986. Some traditional Teetes, G.L., Seshu Reddy, K.V., Leuschner, K., House, pest c o n t r o l practices of S A T farmers. Research M a n a g e - L.R. 1983. Sorghum insect identification handbook. Infor- ment P r o g r a m , Economics G r o u p , V L S Miscellaneous mation Bulletin no. 12. Patancheru, A.P. 502 324, Indi a : Series. Patancheru, A.P. 502 324, India: International International Crops Research Institute for the Semi-Ar i d C r o p s Research Institute f o r the S e m i - A r i d T r o p i c s . Tropics. 124pp. (Limited distribution.) Walker, P.T. 1967. Survey of losses of cereals to pests in Reichelderfer, K.H., Carlson, G.A., and Norton, G.A. Kenya and Tanzania. FAO Symposium on Crop Losses, 1984. E c o n o m i c guidelines f o r c r o p pest c o n t r o l . F A O Rome 2:79-88. Plant Production and Protection Paper no.58. Rome, W a l k e r , T . S . 1987. E c o n o m i c prospects f o r agroforestry Italy: F A O . interventions i n India's S A T : implications f o r research Reichelderfer, K . H . , and Bottrell, D.G. 1985. Evaluating resource allocation at ICRISAT. Resource Management the economic a n d social i m p l i c a t i o n s of a g r i c u l t u r a l pests Program, Economics Group Progress Report no.79. and their c o n t r o l . C r o p P r o t e c t i o n 4(3):281-297. Patancheru, A.P. 502 324, India: International Crops Research Institute for the Semi-Arid Tropics. (Limited Ryan, J.G., Bidinger, P . D . , R a o , N.P., and Pushpamma, P. distribution.) 1984. T h e determinants of i n d i v i d u a l diets and n u t r i t i o n a l status in six villages of southern I n d i a . Research Bulletin Walker, T.S., and Rao, K.V.S. 1982. Yield a n d net r e t u r n no.7. Patancheru, A. P. 502 324, I n d i a : I n t e r n a t i o n a l C r o p s distributions in common village cropping systems in the Research Institute f o r the S e m i - A r i d Tropics. semi-arid tropics of India. Economics Program Progress Report no. 41. Patancheru, A.P. 502 324, India: Interna- Seshu Reddy, K.V., and Davies, J.C. 1979. Pests of t i o n a l Crops Research Institute f o r the S e m i - A r i d T r o p i c s . s o r g h u m a n d pearl millet, a n d their parasites and preda- (Limited distribution.) tors, recorded at 1 C R 1 S A T Center, I n d i a , up to A u g u s t 1979. Cereal E n t o m o l o g y Progress Report no.2. Patan- c h e r u , A. P. 502 324, I n d i a : I n t e r n a t i o n a l Crops Research Institute f o r the S e m i - A r i d Tropics. 23 pp. ( L i m i t e d distribution.)

Seshu Reddy, K.V., and O m o l o , E.O. 1985. S o r g h u m insect pest situation in eastern A f r i c a . Pages 3 1 - 3 6 in P r o - ceedings o f the I n t e r n a t i o n a l S o r g h u m E n t o m o l o g y W o r k - shop, 15-21 J u l 1984, College S t a t i o n , Texas, U S A . Patancheru, A.P. 502 324, India:International Crops Research Institute f o r the S e m i - A r i d T r o p i c s .

Seshu Reddy, K . V . ( I n press.) Assessment of on-farm yield losses in s o r g h u m d u e to insect pests. In Proceedings of the Regional S t u d y W o r k s h o p o n O n - F a r m and Post-Harvest Losses of Cereal C r o p s in A f r i c a D u e to Pests and D i s - eases, 11-15 Oct 1987, M b i t a P o i n t , K e n y a . N a i r o b i , Kenya: International Centre for Insect Physiology and Ecology.

Sharma, H . C . 1985. Strategies f o r pest c o n t r o l in s o r g h u m in I n d i a . T r o p i c a l Pest M a n a g e m e n t 31:167-185.

Tait, E.J. (ed.) 1981. Guidelines f o r research. Perception a n d management of pests and pesticides n e t w o r k , M i l t o n Keynes Buckinghamshire, UK: Open University, Technol- ogy Faculty, Systems G r o u p .

114 D i s c u s s i o n Prem Kishore: The effect of different insecticides used in sorghum stem borer c o n t r o l on natural ene- Reyes: Since older plants (six weeks old) are pre- mies has not been studied in detail. However, data ferred f o r oviposition, is this related to the n u t r i - generated on the effect of endosulfan 4% granules or t i o n a l status of the plant on w h i c h the larvae w i l l dust show that its application does not affect natural feed? enemies. C. partellus has not developed resistance to Harris: Possibly, but I do not have relevant i n f o r m a - insecticides. t i o n . Borers on crop hosts seem to have developed Vidyabhushnam: Delayed planting has been sug- the strategy of going for the youngest tissues. E v i - gested in cultural control of stem borers. But this dence of recent w o r k on Chilo in A f r i c a suggests that practice w o u l d be disastrous in the I n d i a n context, leaf w h o r l tissue is more nutritious. where shoot fly infestation w o u l d surely wipe out a Nwanze: You spoke on the co-evolution of cereals late crop. Moreover, a fortnight's delay in planting and their stem borers. We k n o w that sorghum and w i l l seriously affect the crop expression. Is this pearl millet originated in A f r i c a and that the i m p o r - recommendation therefore of any practical value? tant stem borers are indigenous to Africa. One Varma: The suggestion in question is not a generali- w o u l d have expected that the natural enemies of zation for saving the crop against stem borer. It is stem borers w o u l d have also evolved in parallel w i t h pertinent, however, in regions where shoot fly is not their hosts, but this is not the case. C o u l d y o u please a p r o b l e m . F o r example, in northern I n d i a where elucidate? sorghum is g r o w n for fodder, we sow in July. Harris: This is a relevant question and it is a huge Lukefahr: Do y o u k n o w of an example where the topic. It is a matter of balance; part of the answer is combined action of the native parasites actually that the natural enemies are not operating the stra- suppressed borer population below the economic tegy that y o u w o u l d like them to operate. Further- threshold level? more, the strategy of natural enemies is not aimed at Betbeder-Matibet: A good example is in West A f r i c a eliminating their hosts. M a n y are general parasi- with the sugarcane stem borer, Eldana saccharine. toids or predators developing on a wide range of The natural enemy complex of ants, parasites, and hosts. W h a t we have are specialist stem borers that predators have kept borer damage to less than 5%. we w o u l d like best controlled by highly specialized We have monitored this borer for more than 10 years parasitoids. N o t that many exist. in several sugarcane farms and have f o u n d this level Vidyabhushnam: It was suggested that chemical maintained. W h e n this balance is upset, for exam- control measures should be adopted whenever neces- ple, through the use of insecticides, borer damage on sary. H o w do y o u ascertain which situation warrants stems increases to between 15 and 20%. the use of chemical control? Furthermore, would it Seshu Reddy: In assessing yield loss using various be valid in the case of peduncle infestation? larval densities at various growth stages, what pre- Prem Kishore: The reference to chemical control cautions did you take to eliminate natural infestation? was in the context of determining economic thresh- Taneja: In trials conducted at I C R I S A T Center, olds. Studies on insecticide application to protect crops were planted in mid-June when natural infes- against peduncle infestation are still lacking. This tation is negligible. A n y natural infestation is taken needs to be investigated. into consideration by comparison w i t h the c o n t r o l Sharma: If I have understood correctly, y o u have (zero infestation). Usually this is less than 1% mentioned that carbofuran provides borer c o n t r o l infestation. f o r up to 45 days. In that case, w o u l d you recom- Seshu Reddy: In your studies on avoidable losses mend any insecticide control since at that stage the y o u certainly encountered other sorghum pests such crop will be in the boot leaf stage? as midge and headbugs. W h a t steps d i d y o u take to Prem Kishore: Data f r o m trials conducted on seed protect your crop against these insects so as to have treatment, soil furrow application, or side-dressing accurate data on losses due to stem borer? at 15 days after germinaton indicate that under Taneja: We spray to protect the crop f r o m possible moderate levels of resistance there is no need for panicle feeding pests, as and when required. S i m - another application of carbofuran. ilarly, we use bird scarers against birds. Suryanarayana Murthy: W h a t are the effects of Chundurwar: Y o u have presented the results of y o u r insecticides used in borer c o n t r o l on the natural studies w i t h particular hybrids such as C S H 1. but enemy complex? W h a t are the dangers of borer we need to have results on the released hybrids in resistance to insecticides as we now have in Heliothis? India, especially C S H 5 and C S H 9 f o r comparison.

115 Taneja: We do not have such results and similar support our on-station research with what is really trials w i t h C S H 5 and C S H 9 need to be conducted. happening on the farmers' field. Nwanze: Dr Leuschner has pointed out that the Harris: There are all sorts of technicalities, and tech- effect of stem tunneling on grain yield depends on nical aspects to the issue of whether stem borers are a c r o p age at infestation and p o i n t of borer entry and p r o b l e m or not. W e , as entomologists, may see this attack. However, there are no data to show this. 1 as a p r o b l e m but I t h i n k in m a n y cases farmers do believe that w i t h the stem cage technique, we should not. There must be situations when they d o , and conclusively show that this is the case. Experiments those are the situations that have to be defined so should be designed in this regard. that something practical can be done in p r o v i d i n g Wiseman: This should be a m a j o r p o i n t f o r discus- solutions. These are some of the key issues being sion by Dr Verma's group. considered in this w o r k s h o p . If there are problems, Lukefahr: Based on data provided by Dr Taneja, where are they, and what do they amount to? The one needs to have infestation early in the season with first t h i n g to do is to try and assess the losses, if they a level of infestation that greatly exceeds what one occur. It is not easy, but it is the first step in setting n o r m a l l y expects in the first or second generation. I up proper research programs w h i c h are intended to am w o n d e r i n g if there really is a p r o b l e m in farmers' provide applied solutions. fields. Mueller: There may be a p r o b l e m in farmers' fields but f r o m o u r observations, farmers are not particularly concerned w i t h stem borers. Farmers may have 5 - 1 0 % losses due to borers, but they may have bigger problems such as drought and Striga that dwarf losses due to borers. Nwanze: There are practically no data available f r o m farmers' fields on actual losses due to borers. There are, however, reports on pest incidence. O u r d e f i n i t i o n of a pest is often based on research station findings. We need data that show its magnitude on farmers'fields. We also need to take farmers' percep- t i o n of the p r o b l e m into consideration. Lukefahr: We should be careful, because otherwise y o u set up a research p r o g r a m to see if a problem exists rather than to solve a problem. Nwanze: But that is where the p r o b l e m lies. It is w r o n g to set up a research p r o g r a m based on infor- m a t i o n generated solely f r o m a research station. We must accumulate base line i n f o r m a t i o n on the extent of damage on farmers' fields. Leuschner: H o w w o u l d y o u r decision, in terms of research priorities on stem borer c o n t r o l , be affected in a situation where farmers perceive 15% damage by stem borer as unimportant? Mueller: What is important is farmers' perception of stem borer damage relative to losses f r o m other yield reducers. F o r example, if the same farmers perceive losses f r o m other yield reducers such as Striga to be m u c h higher t h a n 15%, and if this perception is supported by yield loss surveys, stem borers w o u l d not be listed as t o p p r i o r i t y for applied, p r o b l e m - solving research. Seshu Reddy: We cannot solve all the problems in one day. There are several constraints besides insect pests w h i c h the farmers must deal w i t h . We need to

116 Host-plant Resistance

Methodologies Used for Screening for Resistance to Fall Armyworm in Sorghum

B.R. Wiseman1

Abstract

Methodologies used for screening for resistance in sorghum, Sorghum bicolor to fall army worm Spodoptera frugiperda are reported. Screening for seedling and whorl-stage resistance is accom• plished by applying neonate fall armyworm mixed in corncob grits with a mechanical infestation device at the rate of four larvae per 2-day old seedling. For seedlings, visual ratings of leaf-feeding damage are made on a scale of 0-9 when the susceptible control seedling approaches a rating of 9; for whorl-stage plants, visual ratings are made 10 and 14 days after infestation. Evaluations of panicle-stage resistance may be made directly in the field under artificial infestation or in the laboratory using a meridic-based diet bioassay. Resistance in the seedling and whorl stage of leaf development has been located in 1821 cm and at the panicle stage in NK-Savanna 5.

Introduction sorghum, Sorghum bicolor (L.) Moench. However, recently, Heinrichs et al. (1985) published an exten- A thorough understanding of the insect and plant sive volume of techniques on 24 insect species attack- relationship is required before a program of plant ing rice, Oryza sativa. Their w o r k reported on rear- resistance is initiated. Techniques for measuring dif• ing, greenhouse and field screening, mechanism of ferences in damage to cultivars is probably the key resistance, and sources of resistance. M o r e recently, factor in determining the success or failure of any the maize, Zea mays, program at the International program for developing insect resistance (Dahms Maize and Wheat Improvement Center sponsored a 1972). Little comprehensive i n f o r m a t i o n is available comprehensive symposium directed entirely to me- on techniques to infest and evaluate for insect resis- thodology used to determine resistance in maize to tance; such i n f o r m a t i o n is especially lacking on insects. The published proceedings w i l l cover tech-

1. U S D A / A R S , Insect Biology and Population Management Research Laboratory, Tifton, GA 31793-0748, USA.

I C R l S A T (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, ICRISAT Center, India. Patancheru, A.P. 502 324, India: ICR1SAT.

119 nological subjects such as rearing, infesting, and corn e a r w o r m ( C E W ) Heliothis zea (Boddie), and evaluating, mechanisms of resistance, breeding, and F A W cannot be studied together unless a determina- the use of the resistant cultivars in management of t i o n is made that b o t h species have identical prefer- pests. A l l maize insects are presented. ences and that the resistances expressed are identi- Even though extensive and comprehensive tech- cal. This is very doubtful since these insect species nological advances have been made f o r some crops are quite d i f f e r e n t — b o t h in behavior and in host- and insect species, the techniques usually cannot be plant preference. Thus, evaluations for resistance in completely adapted to new insects or crops w i t h o u t sorghum must be such that the t w o insect pests are extensive modifications. But the ideas and applica- separated by time and / or space. This can be accom- tions that have been reported can be readily used to plished when the test insects are mass-reared. develop new techniques f o r each insect pest under investigation. Insect R e a r i n g

F a l l A r m y w o r m The plant resistance p r o g r a m has been greatly enhanced by artificial rearing of the F A W . F A W are M o r e t h a n 190 years have passed since the fall mass-reared on a modified pinto bean diet (Table 1) a r m y w o r m ( F A W ) , Spodoptera frugiperda (J.E. ( B u r t o n 1969, Perkins 1979). The modified pinto S m i t h ) , was first recognized as a serious economic bean diet is used because the wheatgerm-casein diet pest ( L u g i n b i l l 1928). It is one of only a few insects is more expensive and the wheat-soy-blend ( W S B ) that periodically disperse and breed throughout the ( B u r t o n and Perkins 1972) is no longer commer- U.S. The F A W plagues many f o o d crops and grasses cially available ( B u r t o n and Perkins In press). and can limit p r o d u c t i o n of many crops in various areas of the southeastern U.S., Mexico, and Central and South America (Wiseman and Davis 1979). Entomologists w i l l remember 1975, 1976, and 1977 as years of heavy F A W infestations throughout Table 1. Ingredients for the fall armyworm diet and 1 the southeastern U .S. Estimated dollar losses attrib- sources of diet ingredients .

uted to F A W on all crops in the southeastern U.S. in Ingredient g L-1 of diet mL L- 1 o f diet 1975 were $61.2 m i l l i o n and in 1976, $31.9 m i l l i o n , Pinto beans2 120.0 (dry) and the 1977 losses in Georgia alone were estimated Torula yeast3 35.0 at $137.5 m i l l i o n (Sparks 1979). One of the most Ascorbic acid4 3.5 i m p o r t a n t pests of sorghum in recent years in the 5 Wheat g e r m 55.0 southeastern U.S. and in much of Central and South Methyl p-hydroxy America has been the F A W . benzoate6 2.2 The adult of the F A W is nocturnal. At dusk, Sorbic acid7 1.1 adults initiate movement t o w a r d host plants that are Formaldehyde (10%)8 10.0 suitable for feeding and oviposition. Eggs are laid in Water (for mixing above 465.0 clusters and protected by a dense covering of scales. ingredients) 9 Masses contain f r o m a few to hundreds of eggs. Agar 15.0 W a t e r ( f o r agar which hatch in 2-4 days if mean temperatures are solution) 360.0 21.1-26.7°C. As the eggs hatch, the larvae consume the shells and then initiate feeding on the plants until 1 . I n s t i t u t i o n a l W h o l e s a l e , I n c . , P.O. B o x 4 7 4 7 , M a c o n G A 31208. they have completed six instars ( L u g i n b i l l 1928, 2 . L a k e States D i v i s i o n , R h i n e l a n d e r P a p e r C o . , R h i n e l a n d e r , W l Sparks 1979). The sixth instar drops to the ground 5 4 5 0 1 . and pupates in the soil at a depth of about 2.54-7.62 3 . H o f f m a n L a R o c h e , I n c . , 340 K i n g s l a n d R d . , N u t l e y , N J 07110. c m , depending on soil texture, moisture, and temper- 4 . V i t a m i n s , I n c . , 200 East R a n d o l p h D r . . C h i c a g o , I L 6 0 6 0 1 . ature; the life cycle requires about 30 days. 5 . K a l a n a C h e m i c a l , I n c . , 290 R i v e r D r . G a r f i e l d , N J 07026. 6 . 1 C N P h a r m a c e u t i c a l s , 26201 M i l e s R d . . C l e v e l a n d . O H 4 4 1 2 8 . In s o r g h u m , it is necessary to recognize the differ- 7 . Fisher S c i e n t i f i c . P.O. B o x 4 8 2 9 , N o r c r o s s , G A 3 0 0 9 1 . ent instars that cause injury to the plant and the 8 . P e r n y , I n c . , P . O . B o x 7 1 1 , R i d g e w o o d , N J 9 7 4 3 1 . plant stage attacked. Also, it is i m p o r t a n t to deter- 9 . F r o m B u r t o n a n d P e r k i n s ( i n press). mine whether damage was caused by the F A W or by M e n t i o n o f a c o m m e r c i a l p r o d u c t does n o t i m p l y e n d o r s e m e n t b y USDA. similar pest species. M i x t u r e s of larvae such as the

120 Estimated costs for rearing 1000 F A W in 1987 was IPM Breeding about $16.00, exclusive of labor. The F A W has been reared f o r more t h a n 20 years on the artificial diet t h r o u g h 300 or more generations. Plans are afoot to introduce w i l d males into the laboratory culture at least once a year to prevent inbreeding and to keep Biology Ecology the laboratory insects as near to the feral population HPR as possible. F o r details of the day-to-day procedures and techniques f o r rearing the F A W , refer to B u r t o n and Perkins ( I n press).

Physiology Biochemistry P l a n t Resistance

Figure 1. Key areas in which methodology should G r a i n sorghum is one of the most important food be developed for a successful plant resistance and feed grain crops in the w o r l d . L u g i n b i l l (1969) p r o g r a m . stated that "the ideal method of combating insects that attack plants is to grow insect-resistant cultivars". The development and use of plants resistant to pests is essential to most integrated control programs. In fact, Wiseman (1987) showed that the resistant cultivar should be the base f r o m which levels of the three mechanisms of resistance may be integrated pest management strategies arise. present in a plant or cultivar to confer a given degree Plant resistance can be defined as "the relative or level of resistance. amount of heritable qualities possessed by the plant Knowledge of prior research, and the biological w h i c h influences the ultimate degree of damage done developments of the sorghum plant and F A W rela- by the insect in the field " (Painter 1951). This defini- tionship, should precede any new plant resistance t i o n applies today as it did more than 30 years ago. investigation. As shown in Figure 1 (Wiseman 1985 Painter (1951, 1968) classified plant resistance and In press), methodology must be developed in into three mechanisms: nonpreference, antibiosis, several key areas before significant progress can be and tolerance. Nonpreference results when a plant made in the development of sorghum plants resis- or cultivar is used less for oviposition, f o o d , a n d / o r tant t o F A W . shelter. A nonpreferred plant may possess c o m b i n a - Dependable and repeatable techniques must be tions and / or levels of these nonpreferred qualities. developed for any phase of a plant resistance pro- Nonpreference may be further classed as relative or gram to make regular progress (Wiseman et al. absolute (Owens 1975). Relative nonpreference de- 1980a). The techniques must be as simple as possible notes that the pest insect has a multiple choice, and and must be efficient and accurate (Guthrie 1975). absolute indicates that the insect has only one choice The methods that are developed should produce to oviposit, establish, or feed on a particular plant or m a x i m u m difference between the resistant and sus- cultivar. Absolute nonpreference is the stronger of ceptible cultivars (Wiseman et al. 1980b). In addi- the two. Antibiosis relates to the adverse effects (e.g., t i o n , in order to separate the three mechanisms of m o r t a l i t y of larvae, smaller insects, longer develop- resistance a n d / o r various types of resistance w i t h i n ment time, etc.) on the insect which uses a resistant each mechanism, separate and unique techniques plant f o r f o o d . A g a i n , there may be combinations must be developed. and / or levels of these types of antibiosis w i t h i n the same plant or cultivar. Lastly, tolerance describes a plant or cultivar that is able to produce well despite Resistance Evaluations infestations that seriously damage susceptible plants. Tolerant plants may grow and reproduce, repair Greenhouse Screening injury or compensate, or recover f r o m damage to a marked degree in spite of supporting an insect p o p u - Sorghum cultivars were planted (26 per metal green- lation that damages a susceptible plant or cultivar house flat) in fine-washed river sand, in rows 40 cm (Painter 1951, Painter 1968). Combinations a n d / o r long and 2.5 cm apart, for seedling evaluations

121 (20-25 seedlings per entry). We now use a large watering the plants daily to direct the water between metal flat (187.5 cm x 90 cm x 10 cm deep) that the rows and into the alleys to prevent disturbing the accommodates 250 entries per tray. Outside rows are feeding of the larvae. A l l entries are visually rated for bordered w i t h a c o m m o n commercial h y b r i d . W h e n damage when the susceptible control reaches 9, its the seedlings are about 2 days o l d , infestations are m a x i m u m damage rating. Usually this occurs about made w i t h neonate F A W by using the modified the fourth day after infestation. Additional ratings " b a z o o k a " (Wiseman et al. 1980a). For these infesta- on succeeding days may be taken to detect if any tions, large numbers of F A W eggs, laid on paper entries are more resistant than the resistant c o n t r o l . towels, are obtained f r o m the rearing section of the A visual plot rating scale of 0-9 is used, where: laboratory and incubated at about 27° C u n t i l they 0=no damage; 1=small amount of pinhole-type hatch. Larvae are kept in darkness to prevent web- i n j u r y ; 2 = s e v e r a l pinholes; 3 = s m a l l amount o f bing. The larvae are gently shaken f r o m the paper shot-hole type i n j u r y w i t h 1 or 2 lesions; 4 = s e v e r a l towels, mixed w i t h corncob grits and precalibrated shot-hole type injuries and a few lesions; 5=several to a m i x t u r e of about 20 ± 2 neonates per delivery lesions; 6 = several lesions, shot hole injury and t h r o u g h the bazooka. The neonates are dispensed portions eaten away; 7 = several lesions and portions directly onto the sand adjacent to the treatment rows eaten away and areas dying; 8 = several portions of at a rate of 4 larvae plant- 1 (Fig.2). B o t h a resistant the w h o r l eaten away and areas d y i n g ; and 9 = the and susceptible c o n t r o l should be provided when w h o r l completely eaten away and more areas dying possible. Greenhouse temperatures should be main- or plant dead (Wiseman et al. 1966). If more than tained between 27-30° C. Care should be taken when one rating is recorded, then the ratings may be aver-

Figure 2. Infesting sorghum seedlings with F A W neonates mixed in corncob grits using the "bazooka" (Wiseman and Courley 1982).

122 aged, an analysis of variance calculated, and entry Laboratory Screening and means separated by Waller-Duncan multiple range Mechanisms of Resistance test. A b o u t 16000 exotic sorghum cultivars f r o m E t h i o p i a and Yemen have been evaluated to date f o r In order to be completely sure that resistance to seedling resistance. A p p r o x i m a t e l y 100 rated better F A W could b e separated f r o m that o f the C E W than the resistant control. d u r i n g resistance evaluations, we had to develop laboratory procedures that w o u l d ensure the necessary isolation of the t w o pests (Wiseman et al. 1984). Field Screening—Whorl Stage Since F A W are mass-reared on meridic diets, an ample supply of diet materials and insects is avail- Tests are usually planted in the field in a randomized able for laboratory use. The pinto bean diet (Table 1) complete block design w i t h 3 or 4 replications in is used as a base diet in the development of a l a b o r a - rows about 3 m in length and 75 cm apart. Field tory bioassay that incorporated fresh or dried plant infestations are made w i t h 20 neonate F A W larvae materials for subsequent feeding to neonate FAW. per plant, at about the 8-10 leaf stage of develop- Diet preparation for the bioassay is as follows: ment, in t w o applications using a mechanical infes- 1. Pinto bean diet may be requested in b u l k f r o m tation device (Fig.3). Larvae are obtained in a sim- the rearing section of the laboratory or made up ilar manner as that of the greenhouse screening, and in 3.85 L amounts. neonates are dropped directly into the w h o r l . The 2. Plant materials may be processed fresh, freeze- second application should be made no later than 24 h dried, or oven-dried (41°C). after the first to prevent larval competition. Visual 3. If fresh plant materials are used, they must be damage ratings should be made at 10 and 14 days blended in a sufficent quantity of distilled after infesting, using the visual rating scale described water, i.e., 1 2 0 m L of water and 50-60 g of plant above. The damage rating may be a plot rating or material, to m i x w i t h 300 mL of bean diet. F o r ratings of 10 individual plants per plot. The earlier ease in handling, dry plant materials should be rating permits the researcher to obtain differences in used. A b o u t 20 g of d r y plant material is damage by F A W before larval migration is initiated. blended into 250 mL of p i n t o bean diet that has The visual rating at about 10 days can be made using been diluted w i t h 150 mL of distilled water. the scale f o r leaf-feeding resistance as described by These ratios of materials w i l l result in a m i x t u r e Guthrie et al. (1960). that can be readily dispensed. 4. The diet-plant material mixture is dispensed into thirty-six 30 mL (1 oz) or 15 mL ( 5 / 8 oz) Panicle Stage plastic cups in amounts of about 10 mL per c u p , and permitted to solidify for about 2 h. Neonate F A W larvae mixed in corncob grits may be 5. One neonate F A W is placed into each cup after infested directly into the developing panicle at the which the cup is capped. preflower stage to evaluate for resistance in the pani- 6. The treatment cups are numbered and arranged cle stage of development (Fig.4). Larvae are dis- according to the design of the experiment. The pensed at the rate of about 50 larvae per panicle in experiments are maintained in a constant tempe- t w o applications made the same day. T w o applica- rature r o o m at 26.7 ± 2 ° C and 75 ± 5% RH and tions are made to reduce the number of escapes. 14 h light. Usually, 10 or 15 panicles per plot are infested. 7. Individual weights of larvae at 8-10 days after Paper pollinating bags are used to cover the heads to infestation are recorded by using an electronic protect the larvae f r o m c o n t a m i n a t i o n by other balance interfaced w i t h a recording calculator. insect species such as the C E W , and to prevent Days to pupation and weights of pupae, as well adverse environmental effects reducing the infesta- as days to adult eclosion, may also be recorded t i o n . Since visual ratings are difficult to estimate, a f r o m the same experiment. paired uninfested row is used for comparison when 8. A microtechnique is employed when much yield is recorded. smaller amounts of plant materials must be Plot means are used in the analysis of variance, used. Sixty mL of diluted pinto bean diet (800 and Waller-Duncan's multiple range test is applied mL diet:200 mL distilled water) is blended in a to separate mean damage ratings a n d / o r mean microblender w i t h up to 2-3 g of d r y plant yields for the entries. materials. If plant fractions are used, then the

123 Figure 3. Infesting sorghum at whorl-stage with F A W neonates mixed in corncob grits using the "bazooka"

124 solvent and extract must be m i x e d w i t h about 0.5 g of alphacel. The solvent must be evapo- rated t h o r o u g h l y and a solvent check, as well as an alphacel check, provided. 9. The blended mixture is aspirated into about seven plastic soda straws, 0.625 cm diameter by 20 cm length, allowed to solidify and sectioned into 20 mm lengths with each end beveled at about 45° angle to permit easy access to the larvae. 10. T w o soda straw sections are placed into a 15 mL plastic diet cup w i t h one neonate F A W and capped w i t h a polycoated lid to prevent moisture loss f r o m the diet (Fig.5). 11. The experiments consist of t w o cups per repli- cate w i t h 18 replications. The rationale of 18 replications is that the trays hold 36 cups. The analysis of the data uses plot means and is dic- tated by the design of the individual experiments. Panicle spikelets of developing sorghum mixed w i t h pinto bean diets and fed to neonate F A W resulted in differences between weights of larvae at 8 days fed 'NK Savanna 5' (resistant) and ' F u n k H- 5245' (susceptible)(Table 2). Differences in weights of larvae fed the t w o sorghum hybrids were f o u n d at the preflowering, flowering, m i l k , and hard-dough stages of panicle development. No significant relationship was f o u n d between tannin concentration of various stages of panicle development, milk-stage panicles of 12 sorghum genotypes, and weights of F A W larvae. Different types of antibiosis resistance were identified by small larvae, delayed p u p a t i o n , and small pupae. It was found that the glumes (Table 3) of the sorghum panicles confer the highest level of resistance. The next steps are to begin cooperative w o r k w i t h a biochemist and initiate a chemical frac- t i o n a t i o n of the plant part(s) and then use the bioassay to direct us to the desired end product.

S u m m a r y

The F A W can be mass-reared for sorghum resistance evaluations. Methodologies for evaluating sor g h u m for resistance to F A W have been developed. Screening for seedling and whorl-stage resistance of sorghum to F A W is accomplished by applying neonates mixed with corncob grits through the " b a z o o k a " at the rate of four larvae per 2-day-old seedling, and 20 larvae in t w o applications at the 8-10 leaf stage. Figure 4. Infesting sorghum panicle with FAW Visual ratings of leaf-feeding damage are made on a neonates mixed in corncob grits using the scale of 0-9 when the susceptible seedling control " b a z o o k a "

125 F i g u r e 5 . A n e x a m p l e o f m i c r o b i o a s s a y t o d e t e r m i n e differences among entries and/or plant fractions.

Table 2. Weights of F A W larvae after feeding for 8 days on meridic diet supplemented with panicles of two sorghum hybrids and corresponding tannin contents, 1984.

X d u r a t i o n of % tannin1 X larval wt (mg)2 development (days)2 X pupal w t . ( m g ) 2 Stage of panicle F u n k NK F u n k N K F u n k NK F u n k N K development H-5245 S A V . 5 H-5245 S A V . 5 H-5245 S A V . 5 H-5245 SAV.5

C o n t r o l diet - - 254a 269a 14.8a 14.8a 271a 273a Preflowering 3.9 7.7 178c * 214b 14.8a 14.7a 262a 270a F l o w e r i n g 1.0 4.7 200bc * 223b 15.0a 15.0a 277a 274a M i l k stage 0.5 4.9 208 b * 95c 15.2a 17.8b 274a * 177b H a r d d o u g h stage 0.3 7.5 259a * 35d 15.4a 23.1c 207b * 128c

1. T a n n i n d e t e r m i n e d on a d r y - w e i g h t basis. 2. M e a n s w i t h i n each c o l u m n f o l l o w e d by the same letter or means n o t separated by * are n o t s i g n i f i c a n t l y d i f f e r e n t [P > 0 . 0 5 ; D u n c a n ' s (1955) m u l t i p l e range test]. S o u r c e : W i s e m a n et a l . 1986.

126 Guthrie, W . D . 1975. Entomological problems involved in Table 3. Weights of FA W larvae after feeding for 8 days developing host plant resistance programs. Iowa State on merdic diets containing seed, seed and glumes, or Journal of Research 49:519-525. glumes of three sorghum genotypes, 1984. Guthrie, W.D., Dicke, F.F, and Neiswander, C.R. 1960. X larval mass ( m g ) 1 Leaf and sheath feeding resistance to the European c o r n Seed Seed and Glumes borer in eight inbred lines of dent c o r n . Research B u l l e t i n S o r g h u m genotypes only glumes only no.860. Columbus, Ohio, USA: Ohio Agricultural Experi- ment Station. 38 pp. C o n t r o l diet 2 0 1 . 8a A 181. 9a A 183.7aA ( H u e r i n x PI383856) Heinrichs, E.A., Medrano, F.G.,and Rapusus, H.R. 1985. x H u e r i n 130.9bA 146. I b A 23. 9 6 B Genetic evaluation f o r insect resistance in rice. Los Banos, T A M 2 5 6 6 x PI383856 108.8cA 8 1 . 3cB 6.2cC Laguna, Philippines: International Rice Research Insti- SGIRL-MR-2 (selection) 131.8bA 21.0dB 3.4cB tute. 356 pp. 143.3A 107.6B 54.3C Luginbill, P. 1928. The fall armyworm. Technical Bulletin 1. E n t r y means w i t h i n a c o l u m n f o l l o w e d by the same l o w e r case no.34. Washington, D.C., USA: United States Departmen t letter, a n d h o r i z o n t a l seed means f o l l o w e d by the same u p p e r - of A g r i c u l t u r e . 92 pp. case letter, are n o t s i g n i f i c a n t l y d i f f e r e n t [ P > 0 . 0 5 ; D u n c a n ' s (1955) m u l t i p l e range test]. Luginbill, P., Jr. 1969. Developing resistant plants—the S o u r c e : W i s e m a n et a l . 1986. ideal method of controlling insects. Research Report no.111. W a s h i n g t o n , D.C., U S A : U n i t e d States D e p a r t - ment of A g r i c u l t u r e . 14 pp.

Owens, J . C . 1975. An e x p l a n a t i o n of terms used in insect resistance to plants. Iowa State Journal of Research approaches a rating of 9, and at 10- and 14-days after 49:513-517. infestation for whorl-stage sorghum. Evaluations f o r resistance of panicle-stage sorghum can be made Painter, R.H. 1951. Insect resistance in c r o p plants. N e w Y o r k , U S A : M a c m i l l a n . 520 pp. directly in the field under artificial infestation or in the laboratory using a meridic-based diet bioassay. Painter, R . H . 1968. Crops that resist insects p r o v i d e a w a y Resistance in the seedling and w h o r l stage of leaf to increase world food supply. Bulletin no.520. Manha t t a n , development has been identified in 1820 cm and at Kansas, U S A : Kansas A g r i c u l t u r a l E x p e r i m e n t S t a t i o n . the panicle stage of development in ' N K - S a v a n n a 5'. 22 pp. Perkins, W . D . 1979. Laboratory rearing of the fall armyworm. Florida Entomologist 62: 87-91.

Sparks, A . N . 1979. A review of the biology of the f a l l R e f e r e n c e s armyworm. Florida Entomologist 62: 82-87.

Burton, R . L . 1969. Mass rearing the c o r n e a r w o r m in the Wiseman, B.R. 1985. Development of resistance in corn laboratory. Service, United States Department of Agricu l - and sorghum to a foliar- a n d ear/panicle feeding w o r m ture. Report no.HRS-33-134. Washington, D.C., USA; complex. Proceedings o f the A n n u a l C o r n and S o r g h u m United States D e p a r t m e n t of A g r i c u l t u r e . 8 p p . Industry Research Conference 40: 108-124.

Burton, R . L . , and Perkins, W . D . 1972. W S B , a new l a b o r - Wiseman, B.R. 1987a. Host plant resistance in c r o p protec- atory diet f o r the c o r n e a r w o r m and the fall a r m y w o r m . tion in the 21st century. Presented at the 11th Inte r n a t i o n a l J o u r n a l o f Economic E n t o m o l o g y 65:385-386. Congress of Plant Protection, 5-9 Oct 1987, Manila, Philippines. Burton, R.L., and Perkins, W . D . ( I n press.) Rearing the c o r n e a r w o r m and fall a r m y w o r m for maize resistance Wiseman, B.R. ( I n press.) Technological advances f o r studies. Presented at the International S y m p o s i u m on determining resistance in maize to Heliothis zea (Boddie). Methodologies used for Determining Resistance in Maize Presented at the International Symposium on Methodolo- to Insects. 9-13 M a r c h 1987, M e x i c o . A p a r t a d o Postal gies used for D e t e r m i n i n g Resistance in M a i z e to Insects. 6-641, Mexico 6, D.F.:CIMMYT: Centro Internacional de 9-13 March 1987, Mexico. Apartado Postal 6-641, Mexico M e j o r a m i e n t o de M a i z y T r i g o . 6, D.F..CIMMYT: Centro Internacional de Mejoramiento de M a i z y T r i g o . Dahms, R . C . 1972. Techniques in the evaluation and development of host plant resistance. J o u r n a l of E n v i r o n m e n t a l Wiseman, B.R., and Davis, F . M . 1979. Plant resistance to Q u a l i t y 1:254-259. the fall armyworm. Florida Entomologist 62:123-130.

Duncan, D . B . 1955. Multiple range and multiple F tests. Wiseman, B.R., David, F.M., and Campbell, J.E. 1980a. Biometrics 11:1-42. Mechanical infestation device used in fall armyworm plant resistance programs. Florida Entomologist 63: 425-432.

127 Wiseman, B.R., and Gourley, L. 1982. F a l l a r m y w o r m (Lep:Noct.): infestation procedures and sorghum resistance valuations. J o u r n a l o f E c o n o m i c E n t o m o l o g y 75: 1048-1051.

Wiseman, B.R., Mullinix, B.G., and Martin. P.B. 1980b. Insect resistance evaluations: effect of cu l t i v a r p o s i t i o n a n d t i m e o f r a t i n g . J o u r n a l o f E c o n o m i c E n t o m o l o g y 73: 4 5 4 - 4 5 7 .

Wiseman, B.R., Painter, R.H., and Wassom, C.E. 1966. D e t e c t i n g c o r n seedling differences in the greenhouse by visual classification o f damage b y the f a l l a r m y w o r m . J o u r - n a l o f E c o n o m i c E n t o m o l o g y 59:1211-1214.

Wiseman, B.R., Pitre, H . N . , Gourley L., and Fales, S . L . 1984. D i f f e r e n t i a l g r o w t h responses o f f a l l a r m y w o r m l a r- vae on developing s o r g h u m seeds i n c o r p o r a t e d i n t o a m e r i d i c diet. F l o r i d a E n t o m o l o g i s t 67:357-367.

Wiseman, B.R., Pitre, H . N . , Fates, H . N . , and D u n c a n , R . R . 1986. B i o l o g i c a l effects of developing s o r g h u m p a n i - cles in a meridic diet on f a l l a r m y w o r m ( L e p : N o c t . ) devel- o p m e n t . J o u r n a l o f E c o n o m i c E n t o m o l o g y 79:1637-1640.

128 A Review of Sorghum Stem Borer Screening Procedures

K.Leuschner1

Abstract

The stem borer screening procedure developed at ICRISAT Center was evaluated for the stem borer ( C h i l o partellus) infestation pattern in southern Africa. It was found that the existing screening procedure developed at ICRISAT is biased towards an emphasis on deadheart formation and harvestable main heads, not taking into account tolerance as a resistance mechanism. Therefore, the need arose to develop a modified screening system. In order to understand this, an account is given on the host-plant insect interaction leading to various damage symptoms. The value of each damage symptom for the modified evaluation system is discussed and finally the new screening system is presented.

Introduction of evaluation, since many sources of resistance have already been identified. F o r any host plant resistance p r o g r a m it is essential At Southern African Development Coordination to develop a screening procedure based on insect- Conference (SADCC)/ICRISAT, current investi- host interactions. Plant resistance to insects consid• gations include identification of resistant sources ers b o t h the reaction of the host to insect activity and and multilocational testing of material from ICRI- pest p o p u l a t i o n response to the host. I n i t i a l screen• S A T Center k n o w n for its resistance. Since most of ing for plant resistance normally involves quantities this resistance screening is done at national research of diverse material. These studies are intended to stations without the benefit of an entomologist, an distinguish broad differences in the effect on host or evaluation system is needed, one that is both simple insect. In the case of sorghum and the sorghum stem yet accurate enough to detect subtle differences in borer, C. partellus, damage symptoms indicate susceptibility. The stem borer resistance screening activity of the insect on the host. On further testing method currently employed in these investigations is of selected materials the evaluation system should one developed at I C R I S A T Center. It is biased permit more precise definition of the level and t o w a r d an emphasis on deadheart f o r m a t i o n and expression of resistance. Research on stem borer harvestable main heads. W h a t is needed is a screen- resistance at I C R I S A T Center employs b o t h levels ing procedure that puts more emphasis on tolerance,

1. Cereal Entomologist, S A D C C / I C R I S A T Regional Sorghum and Millet Improvement Project, P.O. Box 776, Bulawayo, Zimbabwe.

ICRISAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, I C R I S A T Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

129 w i t h o u t t o t a l l y i g n o r i n g other resistance mecha- about 30-40 days, one stem borer lifecycle is c o m - nisms. Experiences, in the S A D C C region f i n d i n g pleted w i t h the emergence of a new generation of tolerance in material having desirable agronomic moths. T h e second generation moths (if there are characteristics, seems to hold greater potential for discrete generations; usually there are overlapping this w o r k . To date, suitable materials w i t h apprecia- generations) will infest the plant again between ble level of antibiosis have not been f o u n d . In c o n - 45-55 days after seedling emergence. The infestation sidering tolerance as a f u n c t i o n of screening f o r pattern is the same. Larvae w i l l infest the w h o r l , the resistance, it is i m p o r t a n t to consider symptoms of second- and t h i r d - instars w i l l move one or t w o damage as they appear on the plant. These damage internodes below the w h o r l (not to the base), and symptoms can then be further considered in relation enter the stem usually at the leaf axis ( F i g . l c ) . Lar- to their value in a screening system. vae w i l l feed on the already elongated peduncle, or on the closely packed internodes below the fully f o r m e d head if the head is still in the w h o r l . Stem D a m a g e D o n e i n R e l a t i o n t o t h e L i f e tunneling w i l l take place in b o t h cases. If the pedun- C y c l e of C. Partellus cle is out of the w h o r l , feeding w i l l not interfere w i t h peduncle elongation. If the peduncle is not elon- Chilo survives the d r y season in larval diapause. As gated, larvae w i l l tend to feed on the closely packed soon as sufficient moisture is available and tempera- internodes below the growing point (Fig.lc). In cer- ture increases, the diapause is broken and the first tain genotypes this interferes w i t h penduncle elonga- generation of adults appears. Usually the first egg t i o n and the head may become lodged in the w h o r l . masses are f o u n d on sorghum seedlings 10-15 days If peduncle elongation still takes place, larval feed- after emergence. First-instar larvae c l i m b f r o m the ing can damage vascular tissue. If so, incomplete o v i p o s i t i o n site to the w h o r l , w h i c h they enter. They grainfill and partial or complete chaffiness of the feed on the young and tender leaves near the base of head may be observed. If none of these symptoms the w h o r l . This feeding activity is later visible as appear, larvae continue to tunnel the pith of the stem elongated scars on the expanded leaves. This symp- and peduncle. As long as feeding is restricted to the t o m is the first indication of the presence of Chilo pith, grainfill will be normal or only slightly reduced. larvae. Feeding activity continues in the w h o r l u n t i l Weakened by tunneling, however, the peduncle may the larvae reach the second and t h i r d instar (van not be able to support the weight of the head, and H a m b u r g 1980). At this stage they stop feeding, becomes especially susceptible to w i n d damage. leave the w h o r l , and migrate to the base of the seed- Peduncle breakage after physiological maturity will ling where they bore into the seedling base at soil not reduce yield provided the peduncle remains level or a few centimeters above ( F i g . 1a). Entry takes affixed to the stem. place about 8-10 days after hatching, depending on temperature. Feeding inside the seedling base causes t w o symptoms, depending on the position of the Superimposing Factors growing point (Taneja, lCRISAT, personal communication). If f l o r a l i n i t i a t i o n has taken place and Superimposing factors are those which interfere the apical meristem has moved upwards, larvae may w i t h or otherwise influence symptoms, such as feed only on the initial stem ( F i g . 1 b). The s y m p t o m drought, low soil fertility, and molds. For example, is stem tunneling. If the apical meristem is still pres- plant growth is affected, and damage symptoms ent at the point of larval entry, it w i l l be destroyed. appear when larvae feed on or near the apical m e r i - T h e s y m p t o m w i l l be a deadheart. This usually stem. If plant growth is slow due to drought or low happens 30-45 days after germination, or 18-25 soil fertility, damage to vital parts of the stem or the days after egglaying. W i t h the death of the m a i n apical meristem can be influenced. In such a situa- stem, apical dominance has been removed, and a t i o n larval feeding progress may be more rapid than number of tillers f o r m (usually two). The earlier the development of new plant tissue. This prevents these tillers f o r m the greater the chance that they w i l l the g r o w i n g point f r o m m o v i n g ahead of the larval synchronize w i t h the main head development. If no entry point. deadheart is f o r m e d the larvae continue to tunnel Another superimposing factor is rotting. Larval below the growing point until pupation. This activ- stemfeeding in the p i t h n o r m a l l y does not interfere ity weakens the plant, m a k i n g it susceptible to w i n d with plant growth. However, early-feeding activity is breakage. P u p a t i o n takes place in the stem. A f t e r f o l l o w e d by r o t t i n g at an early stage of plant devel-

130 131 o p m e n t , vascular tissue may be damaged, and plant Deadhearts g r o w t h and g r a i n f i l l may be completely or partially interrupted. In all yield loss studies conducted at I C R I S A T and in Z i m b a b w e , deadhearts are one of the most i m p o r - tant factors c o n t r i b u t i n g to yield loss. This parame- D a m a g e S y m p t o m s a n d t h e i r V a l u e ter also gives a good indirect indication of plant f o r R e s i s t a n c e S c r e e n i n g growth status after floral initiation, if we consider the time of infestation in relation to deadheart for- L e a f Fe e di ng m a t i o n (Fig.2). Deadheart f o r m a t i o n is a function of

The present screening system only accounts f o r levels of feeding. Feeding level is rated on a scale, 6 0 - ranging f r o m 1-5 or 1-10, depending on the preference of the scientist involved. F r o m my experience this rating has little value f o r stem borer resistance screening. This is supported by Starks and Doggett (1970) w h o stated that leaf feeding rating was a p o o r 4 0 - indicator of expected grain yield. Results of their study are presented in Table 1. The reason f o r this may be that leaf feeding per se can involve many larvae yet have little impact on yield loss, while yield-limiting damage such as deadhearts and chaffiness can be caused by a single insect. Thus yield loss 2 0 - is not necessarily related to larval density. Rating leaf feeding along a crop row ignores the number of infested plants, and can even base a leaf feeding level on a single plant. Therefore, I suggest that the leaf feeding rating be dropped in favor of a count of the number of plants infested. This w o u l d give an i n d i - cation of the u n i f o r m i t y of the infestation at any 14 17 23 2 9 given point of time. A percentage of infested plants D a y s a f t e r c r o p e m e r g e n c e should be calculated at 25 days after emergence ( D A E ) . This i n f o r m a t i o n w o u l d complement a Figure 2. Deadheart formation in susceptible shoot fly/deadheart evaluation. Multiple observa- sorghum CSH 1 with larval infestation at 14,17,23, tions may be required to screen advanced resistant a n d 2 9 d a y s a f t e r c r o p e m e r g e n c e ( T a n e j a a n d materials. I recommend t w o counts, 20 and 28 D A E . L e u s c h n e r 1 9 8 5 ) .

Table 1. M e a n rating of borer damage on CK 60 sorghum infested with 3 egg masses of C. zonettus plant- - 1 (4 replications)1.

Rating leaf N o . o f Tunnel length Plant height Infestation m e t h o d feeding2 larvae stalk- 1 (cm) ( m )

N o a r t i f i c i a l infestation 2.2 0.4 3.3 69.3 Once i n w h o r l 5.0 3.0 17.8 69.3 2 days apart in w h o r l 5.0 2.7 14.9 67.0 Weekly i n w h o r l 5.3 2.9 9.1 69.5 2 days apart on leaves 5.7 1.8 16.5 59.2

L S D (P = 0.05) 2.5 0.6 6.6 7.4

CV(%) 28.2 17.8 91.7 19.0

1 . T a k e n f r o m S t a r k s a n d D o g g e t t (1970). 2. R a t i n g f r o m 1-9 w i t h 1 = l i t t l e f e e d i n g a n d 9 = severe f e e d i n g .

132 time of infestation (Taneja and Leuschner 1985). evaluated externally, and stem tunneling can o n l y be Therefore deadheart counts and time of infestation measured by splitting the stem, I f i r m l y recommend are essential parameters f o r an evaluation system. discarding stem tunneling as evaluation criteria f o r F o r a rapid screening resistance system, I recom- large-scale screening. Stem splitting should only be mend o n l y one deadheart count, while f o r a more necessary f o r species identification and age d i s t r i b u - detailed screening, deadhearts should be counted t i o n of stem borers, or in the case where fodder twice (35 and 45 D A E ) . Early deadheart and late sorghum is evaluated for stem borer resistance. deadheart f o r m a t i o n leads to tillering. The earlier tillers are f o r m e d , the greater the chance that they w i l l synchronize w i t h the m a i n stem and produce Poor Head Exertion high-yielding heads. Late tillers usually give little or no yield. Therefore, t w o deadheart counts and a P o o r head exertion is an interesting damage criteri- shootfly deadheart count give an indication of the on because it can be caused by genotypes, d r o u g h t , p r o p o r t i o n of m a i n tillers being f o r m e d early or late. or insect infestation. It definitely contributes to yield Late tillering has implications f o r potential yield loss loss. To use it as an evaluation criterion f o r stem even without later stem borer infestation. For final borer resistance, one has to be certain that the stem is yield evaluation, some criteria are necessary in tiller severely infested. This can be done by stripping the selection for practical purposes. I suggest that only top leaves and confirming borer-entry holes. In tillers m a t u r i n g up to 7-days after the main head a d d i t i o n , one has to look at the overall appearance should be sampled. of this parameter. If it is u n i f o r m l y distributed, in a few genotypes it may be genetic. If it is a c o m m o n symptom across genotypes, drought may be a super- Stem Tunneling imposing factor (it was c o m m o n in 1986 in Z i m - babwe, Malawi, and Tanzania where drought was Stem tunneling is a questionable parameter f o r stem prevalent). If p o o r head exertion is sporadic in a borer resistance evaluation. Research at ICRISAT stand, it may be due to stem borers. In any case as it (Table 2) has demonstrated that stem tunneling does contributes significantly to yield loss, it should be not correlate w i t h yield loss if it does not lead to adopted as an evaluation criterion. deadheart formation, poor head exertion, stem breakage, chaffy heads or peduncle breakage before or d u r i n g g r a i n f i l l (Taneja and Leuschner 1985). Complete or Partial Chaffiness This was also reported by Starks and Doggett (1970). These damage parameters are a direct or Complete or partial chaffiness is another damage indirect result of stem tunneling. Since they can be symptom that results from stem tunneling. The

Table 2. Effect of stem borer attack on head and grain yield of sorghum hybrid CSH 1 at Hisar, Haryana, India, 1982.1

M e a n stem M e a n M e a n R a t i o o f g r a i n t o Category t u n n e l i n g (%) head weight (g) g r a i n weight (g) head weight (%)

N o damage 0.0 61.6 52.7 85.3

Stem tunneling U p t o 10% 6.1 62.3 53.2 84.2 1 0 - 2 0 % 14.1 64.0 53.8 83.1 2 0 - 3 0 % 26.3 84.6 69.0 81.5 3 0 - 4 0 % 34.2 79.2 65.0 81.8 4 0 - 5 0 % 43.6 69.2 55.2 79.3 5 0 - 6 0 % 52.8 88.3 71.6 80.6

SE ±1.34 ±10.49 ±9.56 ± 2.70

CV(%) 12 29 32 7

1. S o u r c e : T a n e j a a n d L e u s c h n e r (1985).

133 damage by stem feeding restricts photosynthates should be m o n i t o r e d and is useful in areas where f r o m passing to the head. This c o n d i t i o n may be w i n d damage is prevalent. influenced by d r o u g h t , as seen in the S A D C C region in 1986. It is a straightforward damage criterion w h i c h has already been taken i n t o consideration in Stem Breakage the present evaluation system and should be retained. Stem breakage is an evaluation criterion w h i c h depends not only on tunneling itself but also on stem diameter, stem length, head size, and wind velocity. P a r t i a l G r a i n f i l l N o r m a l l y stem breakage occurs late in the season, and may or may not result in grain loss. This condi- Partial g r a i n f i l l is another difficult criterion to eval- t i o n is especially undesirable f o r mechanized har- uate. It appears to be caused by a c o m b i n a t i o n of vest. Since it holds the potential for significant yield d r o u g h t and stem borer tunneling. I do not recom- loss, stem breakage should be a criterion for screen- m e n d it as a screening factor. In detailed yield loss ing resistance. studies its occurrence could be evaluated by compar- i n g weight by volume samples. Peduncle Tunneling

Peduncle Breakage Peduncle tunneling is part of stem tunneling. Since severe damage is reflected in chaffiness or peduncle This criterion may not be reflected in yield loss as breakage, it is not necessary for penduncle tunneling l o n g as grainfill is n o r m a l and heads have not to be used as a distinct evaluation criterion. d r o p p e d to the g r o u n d . As a screening factor, h o w - ever, it reflects adequate strength of the peduncle, after b o r i n g , in relation to head size. Penduncle Y i e l d strength after b o r i n g may be an i m p o r t a n t consideration for sorghum breeders in avoiding l o n g or weak Since yield is the ultimate criterion in assessing peduncles in relation to head size. This criterion resistance (tolerance) I recommend its regular mea-

Table 3. Comparison of resistance screening procedures.

Existing ICRISAT screening system Proposed modified screening system

25 D A E 1. N o . of plants 1. No. of plants

2. N o . of shoot fly deadhearts 2. N o . of shootfly deadhearts

3. Leaf feeding (score) 3. No. of plants with leaf feeding symptoms

3 5 - 4 5 D A E 1. N o . of stem borer deadhearts 1. N o . of plants 2. N o . of stemborer deadhearts 3. No. of plants with leaf feeding symptoms

A t harvest 1. N o . of plants 1. N o . of u n p r o d u c t i v e heads (evaluate main heads and tillers1 separately)

2. N o . of m a i n heads L u m p p o o r head e x e r t i o n a n d chaffy heads together1

3. N o . of chaffy heads 2. Total no. of productive heads (evaluate main heads and tillers1 separately)

4. Stem tunneling (%) 3. N o . of stems b r o k e n

5. lnternodes no. and no. bored 4. Peduncle breakage 5. Grain yield plot- 1 (taken f r o m m a i n heads and tillers)

1 . O n l y tillers t h a t m a t u r e u p t o 7 days a f t e r m a i n heads s h o u l d b e t a k e n i n t o c o n s i d e r a t i o n .

1 3 4 surement in replicated trials. Even When we have only one r o w per replication it should at least be possible to get an indication of yield across replica- t i o n and locations, in relation to existing stem borer damage parameters. If partially filled heads are present in trials we should assess yield by total grain mass as well as by volume ratios.

Proposed Screening System

Table 3 compares the existing resistance screening system developed at I C R I S A T Center w i t h a p r o - posed, modified screening system. Contents generally reflect the discussion and recommendations made above.

C o n c l u s i o n

The proposed modified screening system has, I believe, the potential to identify tolerance as a part of resistance. At the same t i m e , this system can indicate the likely presence of antibiosis.

R e f e r e n c e s

Starks, K.J., and Doggett, H. 1970. Resistance to spotted stem borer in s o r g h u m and maize. J o u r n a l of E c o n o m i c Entomology 63:1790-1795.

Taneja, S.L., and Leuschner, K. 1985. M e t h o d s of rearing, infestation, and evaluation f o r Chilo partellus resistance in s o r g h u m . Pages 175-188 in Proceedings of the Interna- tional Sorghum Entomology Workshop, 15-21 Jul 1984, College Station, Texas, USA. Patancheru, A.P. 502 324, India: International Crops Research Institute for the S e m i - A r i d T r o p i c s . van H a m b u r g , H. 1980. The grain sorghum stalkborer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae): survival a n d l o c a t i o n of larvae at different infestation levels in plants of different ages. Journal of the Entomological Society of S o u t h e r n A f r i c a 43(1):71-76.

135

Mechanisms of Stem Borer Resistance in Sorghum

S.L. Taneja1 and S. Woodhead2

Abstract

A number of sorghum genotypes resistant to the spotted stem borer (Chilo partellus Swinhoe) have been identified using natural and artificial infestations at ICRISAT. Resistance is attributed to ovipositional nonpreference and antibiosis mechanisms. The major plant characters identified include early panicle initiation and rapid internode elongation. In resistant genotypes, these factors were reflected in the success of first instar larval establishment in the leaf whorl, interval between hatching and larvae boring in the stem, larval mass, and survival rate. Success of the first instar larvae to establish in the whorl is also influenced by physical and chemical plant characteristics. A chemical factor in the surface wax of some sorghum genotypes is associated with larval disorientation.

Introduction is essential to fully understand and utilize resistant genotypes in the management of this pest. Development of sorghum cultivars resistant to the All three types of resistance mechanisms (non- spotted stem borer, Chilo partellus Swinhoe is one preference, antibiosis, and tolerance) defined by of the major research activities at I C R I S A T . A Painter (1951) have been observed in sorghum geno- number of sorghum genotypes resistant to C. partel- types resistant to C. partellus (Jotwani et al. 1971, lus have been identified (Taneja and Leuschner 1978, Jotwani 1978, Lal and Pant 1980, and Da- 1985). Knowledge of these mechanisms of resistance browski and Kidiavai 1983). Experiments have been

1. Entomologist, Sorghum Group, Cereals Program, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Andhra Pradesh 502 324, India. 2. Section Head, Insect Crop Relations, Pest and Vector Management Department, Tropical Development and Research Institute (TDRI), College House, Wrights Lane, London W8 5SJ, UK.

I C R I S A T Conference Paper no. 494.

ICRISAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, I C R I S A T Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

137 conducted at I C R I S A T Center under artificial infes- 1987. Ovipositional nonpreference, as a mechanism t a t i o n and at Hisar under n a t u r a l infestation to d i f - of C. partellus resistance in s o r g h u m has also been ferentiate resistance mechanisms and associated fac- reported on some resistant genotypes by Lal and tors in a set of 20 genotypes, w h i c h have shown Pant (1980), and Dabrowski and Kidiavai (1983). various levels of resistance/susceptibility to C. partellus. Experimental methods have been previously reported (Taneja and Leuschner 1985). Establishment of Young Larvae in the Whorl

The success of newly hatched larvae of C. partellus Ovipositional Nonpreference in attaining the feeding site (plant w h o r l ) varies w i t h cultivar, and some resistant genotypes show a marked This t r i a l was conducted at Hisar d u r i n g the rainy reduction in the proportion of larvae that establish seasons of 1986 and 1987 under n a t u r a l infestations. on the plant. Various factors appear to be responsi• Egg l a y i n g observations were made at 3,4, and 5 ble for this tendency, including environmental effects weeks after crop emergence. (Bernays et al. 1983), and the physical and chemical T o t a l numbers of egg masses were significantly characteristics of the plant ( W o o d h e a d and Taneja higher on the susceptible genotypes ( I C S V 1 and 1987). C S H 1) t h a n most of the resistant ones (Table 1). Detailed observations in the field at I C R I S A T T h e lowest n u m b e r of eggs ( 2 - 3 egg masses per 50 Center showed that the c l i m b to the w h o r l after plants) were recorded on genotypes IS nos. 2309, hatchig was hazardous and, particularly on resistant 5538, 18551, 18573, 18580 in 1986, and on IS nos. genotypes, many larvae never reached their feeding 7224 and 8811 (14-26 egg masses per 50 plants) in site. Hatching normally occurs shortly after dawn when conditions are most favorable f o r success; there is usually little w i n d , and the temperature is low. In order to survive, larvae must reach the w h o r l Table 1. Oviposition of spotted stem borer Chilo partellus expediently, avoiding desiccation as the temperature on 20 sorghum genotypes under natural infestation, Hisar, rises, or being b l o w n off the plant as w i n d speed rainy seasons 1986 and 1987. increases during the day. Also, the longer the time 1986 1987 larvae spend crawling up the plant, the more susceptible they are to possible predators. Several physical Egg mass on Egg mass on characteristics of the resistant genotypes have been G e n o t y p e 50 plants G e n o t y p e 50 plants s h o w n to affect the success of the larvae to reach the IS 2205 32 IS 1044 7 w h o r l , including a disorienting effect that has been IS 2123 10 IS 2376 53 attributed to the chemical composition of the sur- IS 2205 9 IS 4546 46 face w a x of some cultivars (Woodhead 1987). IS 2269 6 IS 5075 46 IS 2309 3 IS 5469 79 IS 4776 9 IS 5470 42 IS 5469 10 IS 5480 44 Physical Characteristics IS 5538 2 IS 5566 33 IS 5585 4 I S 5571 44 O r i e n t a t i o n o f L e a f t o S t e m IS 12308 17 IS 7224 26 IS 13100 10 I S 8811 14 U p w a r d movement of Chilo larvae has been shown 5 IS 17742 38 IS 13674 to result f r o m positive phototaxis (Bernays et al. IS 18333 13 IS 17745 62 1983,1985). As the larvae c l i m b the c u l m they avoid IS 18551 3 IS 17948 55 the shadow cast by the leaves, thus f o l l o w a spiral- IS 18573 3 IS 18578 55 ling path around the culm. Susceptible genoypes IS 18577 7 IS 18584 35 IS 18579 6 IS 18585 52 have f l o p p y leaves m a k i n g an angle greater than 45° IS 18580 2 IS 18677 33 between the leaf and the culm, whereas resistant I C S V 1 25 I C S V 1 104 s o r g h u m cultivars have very erect leaves w h i c h cast C S H 1 41 C S H I 110 little shadow. On these genotypes, larvae continue upwards o n t o the leaves, rather t h a n avoiding t h e m . SE ±4.4 ±14.4 Once on the leaves they eventually c r a w l to the edge, C V (%) 33 25 a n d , on resistant genotypes the orientation of the

138 edge trichomes is such that the larvae tend to move host odor, humidity, and leaf color associated with towards the leaf tip and f r o m there disperse. Even on this pocket are similar to those of the plant w h o r l , susceptible genotypes, some larvae will wander onto explaining the tendency of larvae to remain there. the leaves, fewer disperse after becoming reoriented Larvae are also attracted to the leaf a x i l a n d fre- at the leaf edge. Thus erectness of leaves and orienta- quently remain there f o r some time. Some genotypes t i o n of the leaf trichomes are physical factors that have pronounced ligular hairs and it appears that affect resistance to establishment. Cultivars w i t h larvae may become trapped in these hairs. n a r r o w , erect leaves have long been recognised by These types of mechanisms of resistance appear to sorghum breeders as also resistant to snootily (A t h e - be effective because they delay the larvae in an rigona soccata) ( B l u m 1972). This characteristic is atmosphere of host o d o r and d a r k , simulating c o n - usually associated w i t h glossiness, and is only ex- ditions in the w h o r l . Bernays et al. (1985) reported pressed clearly in y o u n g plants about 15-20 days that the positive phototactic response, essential to after emergence ( D A E ) . In trials at I C R I S A T Cen- m a i n t a i n the directional c l i m b to the feeding site, is ter and Hisar in 1982-84, when 20 genotypes were labile and rapidly lost on entry to the w h o r l It is a screened for resistance under artificial and natural similar effect to that reported f o r the s i l k w o r m infestations, and assessed for physical and chemical Bombyx mori on mulberry, in w h i c h loss of p h o t o - resistance characteristics, the only physical charac- tactic response serves to keep the larvae on their host ter c o m m o n to all resistant genotypes was this trait (Shimizu and K a t o 1978). S o r g h u m genotypes on of erect, n a r r o w leaves ( W o o d h e a d and Taneja w h i c h this type of behavior is observed have lower 1987). rates of c l i m b i n g success and lower final establishment rates, although c l i m b i n g success has less impact in terms of crop loss to stem borer t h a n leaf Detachment of Leaf Sheath from Culm orientation.

A d u l t s of C. partellus frequently lay their eggs on the underside of basal leaves of y o u n g sorghum plants Internode Length f r o m where the newly hatched larvae make their way to the c u l m . These lower leaves can become detached Plant height affects larval success rates in that the f r o m the c u l m , a characteristic more noticeable in further they c l i m b , the more l i k l i h o o d of desiccation some genotypes than in others. Where detachment or attack by predators, and the greater the exposure occurs, larvae have been observed to go behind the to unfavorable environmental conditions. This char• sheath, settle, and attempt to feed there. A l t h o u g h acteristic only operates as a resistance mechanism in this is the favored feeding site for y o u n g larvae of plants where the internodal distances are large, and Sesamia sp, most of w h i c h tunnel into the stem is particularly noticeable in native sorghums that are shortly after hatching, there is no evidence that often tall and thin-stemmed in contrast to the short, y o u n g Chilo larvae can feed successfully on the high-yielding hybrids. tough c u l m , and insects that attempt to feed here rarely survive (Woodhead and Padgham,). Thus the tendency for detachment of the sheath f r o m the c u l m Surface Wax Effects can be an effective resistance mechanism to Chilo establishment. S o r g h u m plants develop a white b l o o m of epicuticular wax (Freeman 1970), which is variable in extent, and genotype dependent (Ayyangar and Ponnaiya Leaf Bases and Ligular Hairs 1941). It is clearly visible to the naked eye in some genotypes (e.g., C S H 1 and IS 1151) and in mature Detailed observations also showed that on approach- plants it forms a thick layer on the c u l m . It has been ing the base of a leaf, particularly on an erect-leafed shown that when this wax layer is conspicuous, it genotype, there was a tendency for larvae to investi- affects c l i m b i n g by Chilo larvae (Bernays et al. gate the basal area of the leaves. On some genotypes 1983). Larvae accumulate wax around their prolegs the edges of the leaf base are tightly curled such that as they move over the plant surface w h i c h impedes a small 'pocket' is f o r m e d that larvae can enter. their progress. Larvae have been f o u n d to c l i m b Some larvae were observed to remain in these almost twice as fast on stems of IS 1151 f r o m w h i c h pockets for several hours. It has been postulated that the wax had been removed, compared w i t h stems

139 p r i o r to removal of w a x . Thus surface w a x can have number of internodes, shoot length, and panicle a gross effect on larval success rates, a l t h o u g h under length. The most significant parameters in resistant wet conditions the superficial w a x is often washed genotypes were found to be the time taken for pani- o f f plants in the field. In general, larvae c l i m b more cle i n i t i a t i o n , and shoot length (Table 2). A l t h o u g h it slowly and have a lower success rate on wet plants, t o o k m o r e time f o r panicle i n i t i a t i o n d u r i n g the an added factor w h i c h complicates interpretation of rainy season, similar trends were observed in most of the importance of a thick w a x layer in resistance. the genotypes. Genotypes with early panicle initia- In a d d i t i o n to the gross effects of thick surface tion escape deadheart formation due to inability of waxes on larval movement, it has been shown that larvae to reach the growing point which would on some resistant genotypes there is a disorienting already have pushed up above larval entry point. effect w h i c h has been a t t r i b u t e d to the chemical T h u s although larvae may feed in the stem and cause composition of the epicuticular w a x (Woodhead t u n n e l i n g , this activity alone m a y n o t cause dead- 1987). It was first observed on y o u n g plants of IS hearts, the critical damage which is associated with 2205 d u r i n g field studies at I C R I S A T Center. A f t e r grain yield loss. Genotype IS 12308 had very early egg hatch, larval progress towards the w h o r l was m o n i t o r e d . A l t h o u g h the p r i m a r y stimulus was positive phototaxis on all genotypes studied, on IS 2205

a behavior pattern was observed w h i c h was charac- R a i n y season terized by hesitation, circling, and stopping c o m - pletely f o r periods of up to several minutes. A l l these 2 0 0 I S 2 2 0 5 activities were accompanied by raising and side-to- I S 5 4 6 9 side m o t i o n of the head and upper abdomen in a I S 12308 searching movement. A p p a r e n t l y , insects were not 150 I C S V 1 biting as they crawled over the plant surface, but were receiving cues f r o m it w h i c h reinforced their T P a n i c l e i n i t i a t i o n upward movement on susceptible genotypes, and 100 disoriented t h e m on resistant ones. E x a m i n a t i o n of the surface of resistant and susceptible genotypes by scanning electron microscopy revealed differences in 5 0 epicuticular wax morphology, which were known to indicate differences in chemical composition (Baker 0 1982). Detailed analysis of surface w a x extracts showed a similar composition for all genotypes with 10 2 0 3 0 4 0 5 0 6 0 the exception of a consistent concentration differ- 160 ence in a c o m p o u n d that co-eluted w i t h the 32 car- P o s t r a i n y season bon n-alkane. This c o m p o u n d was present in very low amounts in the wax of IS 2205, whereas in IS 120 1151 and C S H 1 waxes, the concentration was more than double. It appears that larvae of Chilo identify their host plant by chemical cues received as they 8 0 crawl over the plant surface. If any of the cues is missing, or not sufficiently strong, the insect is disoriented, the u p w a r d c l i m b is interrupted, and fewer 4 0 larvae are successful in reaching the w h o r l and establishing on the plant.

10 2 0 3 0 4 0 5 0 6 0 P l a n t G r o w t h C h a r a c t e r i s t i c s D a y s a f t e r c r o p e m e r g e n c e

Plant g r o w t h was m o n i t o r e d t h r o u g h destructive F i g u r e 1 . S h o o t l e n g t h a n d p a n i c l e i n i t i a t i o n o f samplings at 2-day intervals up to panicle i n i t i a t i o n f o u r s o r g h u m g e n o t y p e s i n r e l a t i o n t o age o f t h e stage, and at weekly intervals thereafter, recording crop, ICRISAT Center, rainy and postrainy plant height, number of leaves, panicle i n i t i a t i o n . seasons 1 9 8 4 / 8 5 .

140 panicle initiation (12 days in postrainy and 17 days Insect Biological Parameters in rainy seasons). A l t h o u g h , the final shoot length in this genotype has been similar to the susceptible In a study on the effect of s o r g h u m genotypes on genotype I C S V 1 ( F i g . 1), it is still resistant to dead- insect biology, using blackhead stage eggs to infest heart f o r m a t i o n because of the shorter time taken to plants 15-20 D A E , it was f o u n d that among the panicle initiation. parameters measured, the most significant ones were Shoot length, i.e., faster internode elongation, has first-instar larval establishment, time interval be- been observed as a significant g r o w t h characteristic tween larval hatching and b o r i n g into the stem, lar- in stem borer resistance. This characteristic also val mass, and survival rate. A lesser proportion of pushes the growing point upward, hampering the larvae became established in the w h o r l in some of the ability of larvae to reach it, and thus preventing resistant genotypes (Table 2), for example, in geno- deadheart formation. In the present study, a number types IS 12308 (25%), IS 13100 (39%), IS 2269 of resistant genotypes with similar panicle initiation (40%), compared with I C S V 1 (51%) and IS 18573 time escaped deadheart f o r m a t i o n due to faster (77%). Chapman et al. (1983) and Bernays et al. internode elongation. For example, two resistant (1983) observed marked differences in the estab- genotypes, IS 2205 and IS 5469, having panicle i n i t i - lishment of first-instar larvae among resistant and ation similar to susceptible I C S V 1, had greater susceptible cultivars. shoot length d u r i n g its g r o w t h period in both sea- In some resistant genotypes, it t o o k more time f o r sons (Fig. 1). the larvae to arrive at the base of the stem f o r b o r i n g .

Table 2. Factors associated with stem borer resistance in sorghum, ICRISAT Center.

Days for S h o o t Larvae Larvae L a r v a l T o t a l Borer panicle length recovered recovered mass insects dead- initia- (cm) i n w h o r l in stem ( m g larva-1) recovered (%) Genotype hearts t i o n 28 DAE1 (%) D A P 10 D A I 21 D A I 28 D A I

IS 1044 44 53 15 54 9 92 28 IS 2123 27 33 21 54 7 93 15 IS 2205 51 39 13 57 16 103 9 IS 2269 - 33 11 40 17 127 22 IS 2309 40 30 14 53 35 85 8 IS 4776 41 40 9 44 10 109 20 IS 5469 22 33 26 57 11 98 25 IS 5538 - 56 6 56 12 99 22 IS 5585 51 33 19 41 9 15 IS 12308 43 17 50 25 31 89 21 IS 13100 45 25 46 39 7 88 18 IS 13674 55 28 24 64 24 101 26 IS 18333 65 53 10 58 21 85 10 IS 18551 48 38 12 62 10 109 23 IS 18573 49 56 6 77 10 140 20 IS 18577 58 51 8 41 21 84 21 IS 18579 49 40 8 42 13 92 15 IS 18580 55 40 11 57 12 99 19 I C S V 1 76 33 10 51 17 115 20 C S H 1 63 28 9 42 13 94 24

M e a n 51 15 99 19

SE ±6.5 ±4.3 ±6.5 ±4.5

CV(%) 18 45 9 33

1. D A E = days a f t e r c r o p emergence. 2 . D A I = days a f t e r i n f e s t a t i o n .

141 This may be due to n u t r i t i o n a l content of particular (leaf orientation, leaf sheath detachment, leaf bases genotypes w h i c h may p r o l o n g the larval period. In and ligular hairs, and internode length), and chemi- genotypes IS 1044, IS 2123, IS 5585, and IS 13100, cal characteristics of the resistant genotypes have less than 10% of the larvae were observed at the base been shown to affect the success of the larvae to of the plant 10 days after the infestation, compared reach the w h o r l , including a disorienting effect. D i f - w i t h 21 % on IS 18333 and 3 5 % on IS 2309 (Table 2). ferent combinations of factors are involved in con- Prolongation of larval period on resistant genotypes ferring resistance in a particular sorghum genotype. was also reported by J o t w a n i et al. (1978). This i n f o m a t i o n is vital f o r borer resistance breeding Larval mass was significantly lower ( < 9 0 mg programs, where resistant sources with diverse mech• larva-1) in six genotypes (IS 2309, IS 5585, IS 12308, anisms may effectively be used either in a pedigree or IS 13100, IS 18333, and IS 18577) compared w i t h IS population breeding approach. 18573 (140 mg larva-1), and l C S V 1 (115 mg larva-1). Survival rate, measured by the t o t a l insect recov- ery, was significantly lower in IS 2205, IS 2309, and IS 18333 (8-10%) compared w i t h 2 8 % in IS 1044 and R e f e r e n c e s 2 4 % in C S H 1. L o w survival rate of C. partellus on resistant genotypes of sorghum have also been Ayyangar, G.N., and Ponnaiya, B.W.X. 1941. T h e occurrence and inheritance of a bloomless sorghum. Current observed by Lal and Sukhani (1979). Science 10(9):408-409. Parameters studied indicate antibiosis mechanisms involved in borer resistance, which have also Baker, E.A. 1982. Chemistry and morphology of plant been observed by many workers (Jotwani et al. 1971, epicuticular waxes. Pages 139-165 in T h e plant cuticle 1978, Lal and Sukhani 1979, and D a b r o w s k i and (Cutler, D.F., Alvin, K.L., and Price, C.E., eds.) Lo n d o n , U K : Academic press. K i d w a i 1983). The present study also indicates that different combinations of factors are involved in Bernays, E.A., Chapman, R.F., and Wood head, S. 1983. c o n f i r m i n g stem borer resistance in various geno- Behaviour of newly hatched larvae of Chilo partellus types. This information is vital for borer resistance (Swinhoe) (Lepidoptera: Pyralidae) associated with their breeding programs. establishment in the host plant, sorghum. Bulletin of E n t o - mological Research 73:75-83.

Bernays, E. Woodhead, S.,and Haines, L. 1985. C l i m b i n g T o l e r a n c e by newly hatched larvae of the spotted stalk borer Chilo partellus to the top of sorghum plants. Entomologia Expe- J o t w a n i (1978) reported significantly lower yield rimentalis et Applicata 39:73-79. loss to stem borers in breeding selections such as 124, Blum, A. 1972. S o r g h u m breeding f o r shoot fly resistance 175, 177, 446, 447, 731, 780, 827, and 829, than in in Israel. Pages 180-191 in C o n t r o l of s o r g h u m shootfly C S H 1, and attributed this to tolerance mechanism. (Jotwani, M.G., and Young, W.R, eds.). New Delhi, India: In spite of severe leaf i n j u r y and stem tunneling in Oxford and IBH Publishing Co. these selections, the final plant stand was very good Chapman, R.F., Woodhead, S., and Bernays, E.A. 1983. and most of the plants had n o r m a l panicles. Similar Survival and dispersal of young larvae of Chilo partellus results were obtained in genotype IS 2205 by Da- ( S w i n h o e ) ( L e p i d o p t e r a : Pyralidae) in t w o cultivars of browski and Kidiavai (1983). sorghum. Bulletin of Entomological Research 73:65-74.

Dabrowski, Z.T. and Kidiavai, E.L. 1983. Resistance of some sorghum lines to the spotted stalk-borer Chilo p a r t e l - C o n c l u s i o n lus under western Kenya conditions. Insect Science and its Application 4(1-2): 119-126. Ovipositional nonpreference, antibiosis, and toler- Freeman, J.E. 1970. Development and structure of the ance type of mechanisms exist for stem borer resis- sorghum plant and its fruit. Pages 28-72 in S o r g h u m p r o - tance in sorghum. The major plant characteristics duction and utilization (Wall, J.S. and Ross, W.M., eds.). associated w i t h resistance are early panicle initia- Westport, Connecticut, USA: AVI Publishing Co. t i o n , and faster internode elongation. Reduced lar- Jotwani, M.G. 1978. Investigations on insect pests of val establishment in the leaf w h o r l , longer time sorghum and millets with special reference to host plant interval between larval hatching and boring into the resistance: final technical report (1972-77). IARI Research stem, lower larval mass and survival rate have been Bulletin (New Series) no.2. New Delhi, India: Indian A g r i - observed in resistant genotypes. Several physical cultural Research Institute.

142 Jotwani, M.G., Chaudhari, S., Singh, S.P., and Young, W . R . 1971. Studies on resistance in s o r g h u m against stem borer, Chilo zonetlus (Swinhoe). Pages 113-118 in Investi- gations on insect pests of s o r g h u m and millets: final technical report (1965-70) ( P r a d h a n , S. et al. eds.). N e w D e l h i , India: I n d i a n A g r i c u l t u r a l Research Institute.

Jotwani, M.G., Srivastava, K.P., Kundu, G.G., Kishore, P., and Sukhani, T . R . 1978. Management of the stem borer, Chilo partellus (Swinhoe), infesting sorghum t h r o u g h the use of resistant varieties a n d chemical c o n t r o l . Journal of Entomological Research 2(2):203-205.

L a l , G.,and Sukhani, T . R . 1979. Development of sorghum stem borer, Chilo partellus (Swinhoe) larvae on some resistant lines of s o r g h u m . Bulletin of E n t o m o l o g y 20:67-70.

Lal, G., and Pant, J.C. 1980. O v i p o s i t i o n a l behaviour of Chilo partellus (Swinhoe) on different resistant and susceptible varieties of maize and s o r g h u m . I n d i a n J o u r n a l of Entomology 42(4):772-775.

Painter, R . H . 1951. Insect resistance in crop plants. New Y o r k , U S A : M a c m i l l a n . 520 pp.

Shimizu, I., and Kato, M. 1978. Loss of p h o t o t a x i s in s i l k w o r m larvae after smelling m u l b e r r y leaves and recov- ery after electroconvulsive shock. Nature 272:248-249.

Woodhead, S. 1987. T h e influence of surface chemicals of s o r g h u m on the behaviour of the stemborer Chilo partellus (Swinhoe). Page 425 in Insects-Plants: proceedings of the V I I n t e r n a t i o n a l S y m p o s i u m o n Insect Plant Relations, J u l 1986, Pau, France. Dordrecht, Netherlands: W. Junk.

Woodhead, S., and Taneja, S.L. 1987. T h e importance of the behaviour of y o u n g larvae in s o r g h u m resistance to Chilo partellus. Entomologia Experimentalis et Applicata 45:47-54.

143

Considerations in the Development of a Host-plant Resistance Program Against the Pearl Millet Stem Borer

M.J. Lukefahr1

Abstract

The stem borer (Coniesta ignefusalis,) is a key pest of pearl millet in the Sahelian region of West Africa. Several cultivars and breeding lines appear to sustain lower populations of this insect compared to local landraces. These differences have not been quantified in trials designed to measure levels of insect resistance. The major constraint in these trials is the nonuniform distribution of natural infestations. In experiments at the ICRISAT Sahelian Center, emphasis is being placed on 1. developing methods to augment natural populations, 2. establishing p o p u l a - tion levels that give repeatable and statistically significant results, 3. determining optimum plot size, 4. determining the sample size needed to measure differences at various population densities, and 5. determining economic thresholds for levels of resistance needed to avert economic losses.

A review of the literature shows that sources of are actually being grown. The reason for this appar- insect resistance has been f o u n d for the major plant ent disparity is pertinent to this presentation. The pests which attack important agricultural food crops. HPR program at ICRISAT Sahelian Center in F o r more than 100 insect species, sources of plant Niamey, Niger, is currently being organized to w o r k resistance have been identified (Harris and Frede- w i t h pearl millet, Pennisetum americanum, and w i l l riksen 1984). Even so, few insect-resistant cultivars become operational in 1989. By this time certain

1. Principal Cereals Entomologist, ICRISAT Sahelian Center, B.P. 12404, Niamey, Niger.

I C R I S A T Conference Paper no. CP 493.

ICR1SAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, ICRISAT Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

145 basic studies w i l l have been completed w h i c h are cially those sources offering the greatest probability fundamental to a successful H PR p r o g r a m . Some of of success. A generally held assumption, not always the concepts and principles being considered f o r this applicable, is that the most likely source of resistance p r o g r a m are presented. is f r o m areas where an insect is endemic. Regardless of the origin of resistance, it is of limited use if it is not: (1) heritable; (2) relatively T h e S e a r c h f o r S o u r c e s o f R e s i s t a n c e permanent; and (3) compatible w i t h desired agronomic qualities. If these three conditions do not The search for plants resistant to insects is the first exist, the resistance source may never be utilized step towards developing a pest-resistant cultivar. even t h o u g h the plant may actually be i m m u n e to Most groups of potentially useful breeding stock are insect attack (Harris and Frederiksen 1984). so large, that screening every genetic variant or available accession is impractical. In the case of millet, more than 15000 germplasm accessions are I d e n t i f i c a t i o n o f R e s i s t a n c e available f o r screening. If 1000 were screened each year, it w o u l d require more than 15 years to com- M a n y different systems have been used to identify plete the process. N o w entries are being added every plant resistance to insects. Some are based on obser- year, therefore compromises must be made when vations of plant populations subjected to a pest epi- selecting lines to be screened f o r resistance. These demic. Valuable i n f o r m a t i o n can be obtained f r o m decisions are especially i m p o r t a n t to developing a such observations, but carefully designed experi- pest-resistant cultivar, since the end-product is p r i n - ments are needed to measure insect populations on cipally dependent u p o n the initial choice of potential the host before deciding whether the plant is resis- resistant sources. tant. By definition, a plant that supports fewer pests The search f o r resistance should be conducted to than another plant, but suffers unacceptable losses, obtain the best sources of resistances w i t h a m i n - cannot be considered as resistant. The mechanisms, i m u m expenditure of money, time, effort, and man- however, that result in reduced insect populations power. Painter (1951) in his b o o k " H o s t Plant may provide valuable selection criteria in the devel- Resistance," suggests that host resistance should be opment of an insect-resistant plant. These are the sought first w i t h i n the crop species and secondly products of research. f r o m the closely related species that w i l l produce fertile progeny when crossed. He also advocates using those lines w h i c h are adapted to an area where the resistance is to be used. However, this approach General Knowledge of the Biology does not optimize the chance of f i n d i n g the best of the Target Pests source of resistance unless these sources are ran- d o m l y distributed. It is i m p o r t a n t to k n o w the number of generations a The continued presence of an insect in a system pest has each c r o p p i n g season, as well as the relative indicates that it has been able to overcome defense rate of increase per generation that the pest under- strategies that the plant developed. If this is the case goes. Tables 1,2,3, and 4 illustrate the importance of it is not likely that the insect p o p u l a t i o n has adver- this i n f o r m a t i o n in designing a suppression p r o g r a m sely affected the plant f o r a significant period of based on chemical control or host-plant resistance. time. Defence mechanisms that the plant has been N o t e f r o m Table 1 that strategies needed to con- able to develop p r o b a b l y co-evolved w i t h the pest. If t r o l an insect w i t h a 10-fold rate of increase w i l l be this d i d not happen, the insect w o u l d probably have different f r o m those needed to c o n t r o l a pest having never reached the status of a pest. only a 2-fold rate of increase. Without this informa- M o s t sources of host resistance to insects pres- tion, it would be difficult to know levels of plant ently being utilized in agriculture consist of plant resistance necessary to avert economic losses. material that have evolved in the absence of insects T h e number of generations that a pest undergoes to w h i c h they are resistant ( H a r r i s 1980). Resistance d u r i n g the c r o p p i n g season is equally i m p o r t a n t . in these instances is f o r t u i t o u s and has a pleitropic Table 2 illustrates this point showing 10- and 5-fold basis since evolutionary selection has not been rates of increases f o r five consecutive generations involved. Useful resistance is so i m p o r t a n t that it d u r i n g a g r o w i n g season. It is obvious that strategies must be obtained f r o m any available source, espe- used to suppress an insect w i t h t w o generations per

146 year and a 5-fold rate of increase w o u l d be different and that the rate of increase per generation probably f r o m one having five generations a season w i t h a does not exceed 10-fold. 10-fold rate of increase. Table 3 shows natural mortality in a stem borer There have been numerous studies on the field population taken from millet stalks left standing in biology of the millet stem borer Coniesta (Acigona) the field. Survival of this insect is greater in stalks left ignefusalis which can contribute to the development standing in the field than in stems exposed to high of an insect-resistant plant. For example, field stud- soil surface temperatures (Harris 1962). Since it is ies indicate that, in most of the range occupied by the c o m m o n practice by growers to u p r o o t millet plants millet stem borer, there are two generations per year, d u r i n g the dry season, the degree of mortality will be much greater than that shown in Table 3. A conservative estimate w o u l d be that less than 500 larvae per hectare survive the postrainy season. Table 1. Levels of suppression needed to stabilize a popu- Other factors such as irregular emergence patterns, lation with different rates of increase (Knipling 1979). and the inability to find a mate w i t h i n the short life Percentage of control span of the adults, tend to support this estimate. Net increase levels above n o r m a l hazards Using this figure (500) as a realistic estimate, we can potential required for each generation project the populations that we must deal with in the per generation to stabilize a population development of millet that is resistant to stem borer 20 95 (Table 4). Levels of resistance that will be needed to 10 90 maintain a stabilized population during the g r o w i n g 5 80 season can also be projected (Table 5). The u n k n o w n 3 67 quantity in this exercise is the levels of infestation 2 50 that can be tolerated before economic losses occur. However, it would not be unrealistic to expect this

Table 2. Rate of increase of two insect populations for five consecutive generations.

5-fold 10-fold Generation increase rate increase rate Table 4. Estimated population levels of the millet stem borer under naturally occurring conditions. 1 100 100 2 500 1 000 No. adults ha- 1 surviving 500 3 2 500 10000 to infest new crop 4 12 500 100 000 First generation 5 0 0 0 5 62 500 1000 000 Second generation 50 000

Table 3. Summary of dry stem examination for diapause larvae of Coniesta (Acigona), lCRISAT Sahelian Center, Sadore, Niger, 1986/87 dry season.

N o . o f N o . o f N o . o f Estimated stems live larvae p o p u l a t i o n Reduction N o . o f - 1 -1 M o n t h examined larvae stem ha (%) pupae

N o v 1725 2711 1.57 51 810 - 0 Dec 2075 2400 1.16 38 280 26.1 0 Jan 1350 1078 0.79 26 070 49.7 0 Feb 1700 1578 0.93 30 690 40.8 0 M a r 1775 1186 0.66 21 780 58.0 0 A p r 1645 655 0.4 13 200 74.2 0 M a y 1100 328 0.3 9 900 80.9 0 J u n 825 168 0.2 6 6 0 0 87.3 0 1 J u l 921 48 0.05 1 716 96.7 82

1. First p u p a e f o u n d d u r i n g the week s t a r t i n g J u l y 7. 1987.

147 facility to rear the millet stem borer. W h e n c o m - Table 5. Different levels of suppression and influence on pleted, it w i l l have the capability to produce large rate of increase of an insect with 10-fold rate of increase per numbers of eggs or first-instar larvae that can be feneration. used to o b t a i n a u n i f o r m level of infestation in Suppression/generation (%) Uncontrolled screening trials. Other methods of augmenting the Generation p o p u l a t i o n natural populations are being investigated, such as 50 80 90 d i s t r i b u t i n g stalks containing diapausing larvae at 1 5 0 0 0 2500 1000 500 different densities within the test blocks. This me- 2 50000 125000 2000 50 t h o d , however, does not have the precision that can be obtained using eggs or newly hatched larvae. The level of infestation that is desirable f o r screening purposes has not been determined, but this level level to be less than 10 000 larvae per hectare, in w i l l p r o b a b l y be 5 0 % of infested plants w i t h i n the w h i c h case the level of resistance needed w o u l d be plot. The problems of "over-infesting", and masking less than 8 0 % and should be an attainable goal. low levels of resistance, must be considered. It is unlikely that singular materials will be found which can impart a desired level of resistance. Several dif - ferent sources of resistance must be found, that can M e t h o d o l o g y f o r a H P R P r o g r a m be accumulated to achieve the desired level of suppression. A host-plant resistance p r o g r a m begins w i t h collections that have characters or traits that are u n k n o w n . This is complicated by the variability that can be Methodology to Incorporate expected w i t h i n an entry, since many plant introduc- Resistance into Elite Lines tions are hetergenous. Harris and Frederiksen (1984) listed three criteria that are pertinent to any screen- Numerous sources of plant resistance have been ing p r o g r a m designed to detect plant resistance: identified but only a few have been incorporated into 1. Field studies should ensure that the stressing agronomically acceptable cultivars. The principal agent is u n i f o r m l y distributed. reason for this apparent disparity is probably the 2. Resistance should be expressed by a component inability to recover resistant factors in segregating of the population being screened. populations. Techniques appropriate f o r field and 3. The epidemic should not overwhelm the factors laboratory screening of resistant or susceptible lines that contribute to resistance. may not be appropriate for recovering resistant W i t h lepidopterous insects, populations tend to plants in a segregating p o p u l a t i o n . O n l y rarely w i l l a be c l u m p e d , so infestations are not u n i f o r m w i t h i n resistant source be f o u n d in an agronomically accep- the test area. Failure to have this capability could table cultivar. More often, resistance must be trans- result in a failed program. This can be illustrated by ferred f r o m an u n i m p r o v e d parental source to one an example f r o m a p r o g r a m that was designed to that is agronomically acceptable. f i n d resistance to the c o t t o n l e a f w o r m , Alabama When resistant and susceptible lines are crossed, argillicea H u b . In a nonreplicated screening t r i a l , the inheritance w i l l fall into one of three categories: 2200 entries were planted, w i t h 10% of the entries as 1. M a j o r genes w h i ch show typical Mendelian ratios susceptible standards. Of these standards, 27% were in F2 generations. rated as being resistant and the remainder were rated 2. M i n o r genes that continue to show v a r i a t i o n f o r susceptible. In this test the standard was t r u l y sus- resistance level in segregating populations. ceptible but the insect p o p u l a t i o n was so p o o r l y 3. Combinations of major, minor, and modifier distributed w i t h i n the test area that no meaningful genes. Harris and Frederiksen (1984) indicate results could be obtained. Relating this example to that the inheritance of resistance has been worked the millet stem borer, a clumped d i s t r i b u t i o n w i t h i n out in only 33 of more than 100 species of the test area c o u l d be even more problematic as the reported insect-resistant plants. From this group, insect is a m u c h weaker flyer than the cotton leaf- resistance was d o m i n a n t in only 17 species, sug- w o r m (moth). gesting that most sources of insect resistance will Early in our w o r k , we recognized this p r o b l e m of be of a recessive nature, or controlled by minor or uneven d i s t r i b u t i o n and assigned high p r i o r i t y to a modifier genes. To recover these resistant genes

148 in segregating populations, precise methods are needed, methods that are generally not available. This factor alone may account for the lack of resistant cultivars, even though good resistant parental sources have been identified.

D i s c u s s i o n a n d C o n c l u s i o n

The probability of developing a millet cultivar for West A f r i c a that is truly stem borer-resistant is good for a number of reasons. First, the insect has only t w o (under most conditions) generations each g r o w i n g season. The overwhelming popula- t i o n pressures that result f r o m insects that have f o u r or five generations per growing season are lacking. Second, there is no evidence of long- range m i g r a t i o n , so researchers w i l l be dealing w i t h local populations. T h i r d , there is not a c o m - plex of stem borers in most of the Sahelian region, therefore if a resistant source could be utilized for p o p u l a t i o n suppression there w i l l not be another borer to fill the " n i c h e " that was occupied by C. ignesfusalis. Finally, I C R I S A T ' s millet germplasm bank contains more than 15 000 accessions of w h i c h approximately 5 0 % originated outside the area that is occupied by the millet stem borer.

R e f e r e n c e s

Harris, K . M . 1962. Lepidopterous stem borers of cereals in Nigeria. Bulletin of Entomological Research 53:139-171.

Harris, M . K . 1980. Searching f o r host plant resistance to a r t h r o p o d s in agriculture. E P P O Bulletin 10 (3):349-355.

Harris, M.K., and Frederiksen, R.A. 1984. Concepts and methods regarding host plant resistance to a r t h r o p o d s a n d pathogens. Annual Review of Phytopathology 22:247-272.

Knipling, E.F. 1979. The basic principles of insect p o p u l a - t i o n suppression and management. U S D A A g r i c u l t u r e Handbook no. 512. Washington, D.C., USA: United States D e p a r t m e n t of A g r i c u l t u r e .

Painter, R . H . 1951. Insect resistance in crop plants. New Y o r k , U S A : M a c m i l l a n . 520 pp.

149 D i s c u s s i o n feeding should be taken into consideration while selecting a line. Nwanze: I t h i n k it is necessary that we also l o o k at Saxena: Dr Wiseman showed that the nonprefer- leaf feeding resistance during the whorl stage. A high ence of the army w o r m for different resistant sorghum level of leaf feeding resistance, whether nonprefer• varieties could be f o r feeding or f o r oviposition. B u t , ence or antibiosis will certainly reduce larval popula• we f i n d that a t h i r d aspect of nonpreference may be tion and consequent deadheart formation. We need f o r orientation to plants, as distinct f r o m orientation to identify w h a t type of resistance we are dealing to nonplant characters or settling response. w i t h . We should also remember that we are talking Wiseman: I showed a general overview of nonpref• about H P R as a component in the management of erence. Yes, when nonpreference is b r o k e n d o w n stem borers. Do we then need very high levels of into the various factors, orientation w o u l d certainly resistance? Do we need to produce cultivars w i t h less be included. t h a n 2 5 % deadhearts? Lukefahr: W h a t is the relationship between the Srivastava: Has anyone observed the behavior of a greenhouse, w h o r l , and panicle resistance tests? If C. partellus larva where it simply cuts an incision on y o u select 100 lines in a greenhouse test, h o w many the g r o w i n g p o i n t and goes away? T h e cu tti n g of the exhibit w h o r l and panicle resistance in subsequent g r o w i n g points leads to the f o r m a t i o n of deadheart, tests? but the rest of the plant does not show any damage Wiseman: Probably very few, if any. It is extremely s y m p t o m . useful to find resistance to more than one stage of Saxena: Yes, we have observed this phenomenon. plant development. Seshu Reddy: A l l damage parameters must be taken Nwanze: Does the methodology y o u use in green• i n t o consideration f o r the evaluation of a line. W i t h house screening permit y o u to identify material w i t h only one parameter it is difficult to adequately eval• moderate levels of resistance, since y o u rate your test uate stem borer resistance in a cultivar. material only after the susceptible c o n t r o l reaches a rating of 9? Wiseman: Yes, I simply observe the material earlier or slightly before the susceptible c o n t r o l approaches a 9 rating. But o u r goal was to f i n d higher levels of resistance t h a n the resistant c o n t r o l . Saxena: H o w d i d y o u do the w a x coating on the surface? W h a t was the experimental design to explain larval movements? Woodhead: Leaf models were prepared and the sur• faces were waxed f o r measuring the larval move• ment. Speed and the direction of the larval move• ments were also ascertained. Vidyabhushnam: W h a t selection criteria should be f o l l o w e d f o r breeding s o r g h u m f o r resistance to C h i l d ? In my o p i n i o n leaf feeding is the best method. Ajayi: In Nigeria, we have a complex of borers attacking sorghum. Sesamia does not feed on leaves, so leaf damage cannot be generalized as a criterion f o r screening. Taneja: The m a i n criterion is deadheart of seedlings, w h i c h is highly correlated to yield loss. I suggest that the test material be planted at peak pest activity in the hot spot areas. Where possible, use u n i f o r m artificial infestation. Leuschner: Leaf feeding scores should be done twice, as deadheart f o r m a t i o n depends on many factors. Guthrie: Deadheart alone is not dependable, leaf

150 Breeding for Resistance

Screening and Breeding Rice for Stem Borer Resistance

M.B. Kalode1, J.S. Bentur2, and T.E. Srinivasan3

Abstract

Progress on the development of rice varieties with resistance to stem borers in Asia has been slow. The reasons for this are the lack of suitable germplasm and screening techniques and a poor understanding of the genetics of resistance. In spite of this, efforts have been made at national and international levels to accumulate genes from moderately resistant genotypes. Such genotypes include ARC 6107, ARC 6044, RYT 2908 (vegetative stage), ARC 6215. ARC 6579. ARC 5757 (heading stage), and ARC 5500, Manoharsali (vegetative and heading). In multilocational testing, promising breeding lines have also been identified from crosses such as Phalguna x TKM 6 (RP 2199) and Swarnadhan x Velluthacheera (RP 2068). Resistance in Phalguna x TKM 6 appears to be polygenic. Moderately resistant varieties like IET 2815, lET 2812, IET 31I6, and IET 3127 are useful in integrated pest management programs.

Introduction assumed importance particularly in hilly areas of Uttar Pradesh. Other species, which cause concern M o r e than 20 species of rice stem borers, mainly only in certain years, include striped borer Chilo Pyralidae and Noctuidae, constitute the major insect suppressalis Walker, the dark headed borer C. pests on rice throughout the w o r l d . In India, the polychrysus M e y r i c k , and the white borer S. inno- yellow stem borer Scirpophaga incertulas Walker is tata Walker. the most predominant species and occurs in most of Several estimates are available on yield losses due the rice-growing areas of the country. A n o t h e r spe• to stem borer damage ( M a t h u r 1983). Experiments cies, Sesamia inferens Walker, the pink borer, has at the Central Rice Research Institute (CRRl), Cut-

1. Senior Entomologist and Head, Directorate of Rice Research (DRR), Rajendranagar, Hyderabad, Andhra Pradesh 500 030, India. 2. Entomologist at the same location. 3. Senior Rice Breeder at the same location.

ICRISAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, ICRISAT Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

153 tack, I n d i a revealed that a I % increase in deadhearts Table 1. Performance of selected rice germplasm entries decreased yield by 0.28% and every unit increase in against the stem borer. white earheads resulted in a yield loss of 0.624%. 1 C o m b i n e d damage of deadhearts and white ear- No.of seasons recording promising heads resulted in a 0.355% yield reduction. Damage reaction at simulation studies at the International Rice Research E n t r y Vegetative stage Heading stage Institute ( I R R I ) , Philippines indicated that 10% Manoharsali 6 5 deadhearts under greenhouse conditions caused A R C 5500 5 6 yield losses of 10%, while 10% deadhearts under field A R C 6107 6 conditions resulted in 5% yield loss. On an average, A R C 6044 4 1 stem borer damage in tropical Asia is estimated to A R C 6215 4 cause 5-10% losses, while in I n d i a 3-95% losses are A R C 6579 2 4 reported. Field experiments in endemic areas, in A R C 5757 4 3 plots protected against stem borer damage, realized 1 . W i t h less t h a n 6 0 % d a m a g e d p l a n t s a t vegetative stage o r 1 5 % a t -1 additional grain yields of 500-1000 kg ha . ( A I C R I P h e a d i n g stage. 1986). T h o u g h rice varieties have been k n o w n to display differential reactions against stem borers f o r more than 70 years, progress on development of resistant ing if plant damage did not exceed 60% at vegetative varieties is relatively slow and not spectacular. Early stage or 15% at heading stage. D u r i n g the 1984 attempts made in this direction have been reviewed postrainy season, the seventh season of testing, test by Israel (1967) f o r I n d i a , Pathak (1967) for the entries were finally rated f o r their performance. Philippines, and by M u n a k a t a and O k a m o t o (1967) The highest damage among the test entries re- for Japan. M o r e recent w o r k in Asia is covered by corded at vegetative stage d u r i n g the course of eva- Heinrichs (1980) while C h o u d h a r y et al. (1984) luation ranged from 66% (ARC 6158 and ARC 6579 exhaustively reviewed the status of varietal resis- d u r i n g the 1981 rainy season) to 9 3 % ( A R C 15831 tance in Asia. In this paper we summarize recent d u r i n g the 1981 postrainy season). At heading stage, research on the identification of resistant donors and highest damage ranged f r o m 4 4 % ( A R C 6215 d u r i n g promising breeding lines at the A i l I n d i a Directorate the 1982 rainy season) to 6 2 % ( A R C 6107 d u r i n g the of Rice Research ( D R R ) , H y d e r a b a d , and under its 1981 rainy season). Despite selection of damage-free A l l India C o o r d i n a t e d Rice I m p r o v e m e n t P r o g r a m plants d u r i n g every generation, only 5 entries out of ( A I C R I P ) at multilocations. 36 tested showed relatively consistent performance in at least one of the g r o w t h stages d u r i n g 3 or more testing seasons (Table 1). S c r e e n i n g R i c e G e r m p l a s m a n d Plant damage in the most promising entries dur- B r e e d i n g L i n e s a t D R R ing the 1984 postrainy season (Table 2) highlighted

T a k i n g advantage of consistently high levels of yellow stem borer incidence d u r i n g b o t h wet (rainy season) and dry (Postrainy season) seasons in exper- Table 2. Percentage damage in selected germplasm acces• imental farms at Rajendranagar and Ramachan- sions by stem borer, postrainy season, 1984. d r a p u r a m , a total of 289 germplasm entries were D a m a g e (%) at evaluated. Based on intitial screening f r o m the 1980 rainy season, 36 selected entries were further tested E n t r y Vegetative stage Heading stage for six consecutive seasons (1981 postrainy season Manoharsali 33.5 3.7 t h r o u g h 1983 rainy season). A R C 5500 51.9 12.3 D u r i n g each of these seasons, selections were A R C 6215 57.2 33.9 made of at least 10 damage-free plants (no deadheart A R C 6579 68.7 5.0 a n d / o r white earhead) in each of the promising A R C 5757 71.0 8.2 entries. Progenies of these plants were tested the T K M 6 60.7 19.6 f o l l o w i n g season at b o t h test locations. Entries were I E T 2815 evaluated on a percentage basis of affected plants. (Sasyasree) 39.2 17.8 Jaya 60.7 30.3 Performance of a test entry was considered promis-

154 the performance of new donors compared w i t h the over locations (Table 3). Significantly, four of the standard resistant c o n t r o l T K M 6 and the released donors, Manoharsali, ARC 5500, ARC 6044, and resistant variety Sasyasree. T w o of the donors, ARC 6215, selected on the basis of their evaluation M a n o h a r s a l i and A R C 5500, displayed better reac- at Hyderabad, continued to display good perfor- t i o n at b o t h vegetative and heading stages, while mance in multilocational testing. Good pest resis- A R C 6579 and A R C 5757 showed a lower level of tance was also seen in R Y T 2908 at vegetative stage, damage at heading stage. Reaction of these donors and in Co 18 and W 1263 at b o t h vegetative and was better than the resistant control T K M 6. A R C heading stages. 6215, despite consistency in earlier testing, showed A m o n g the breeding lines, selections f r o m the only marginal resistance at vegetative stage, and cross Phalguna x T K M 6 ( R P 2199) figured p r o m i - b o t h A R C 6107 and A R C 6044 showed higher d a m - nently. One of the selections f r o m the cross Swar- age t h a n in earlier testing. Further studies on the nadhan x Velluthachera (RP 2068-18-2-9) was also extent of damage and mechanisms of resistance in rated as promising. Several multiple-resistant lines selected varieties are in progress. have been developed f r o m this cross and are currently being evaluated against stem borer.

Multilocational Tests Inheritance of Resistance AICRIP multilocational varietal screening trials against stem borers were reintroduced in 1983 with Inheritance of resistance to yellow stem borer in the the c o n t r i b u t i o n of promising donors and breeding cross P h a l g u n a / T K M 6 has been studied by Prasad lines f r o m different institutions and universities. A et al. (1984). On the basis of damage at heading total of 142 entries have been tested so far at 10-20 stage, resistance to stem borer was observed to be test locations across the country. governed by 3 dominant genes and 1 d o m i n a n t Since the severity of pest load at test locations inhibitory gene, resulting in a ratio of 27:229 (tole- varied considerably, entries were chosen for retest- rant:susceptible) progenies in F2 generation. Furth- ing on the basis of their relative performance over ermore, based on joint segregation, linkage was locations. F o u r years of testing identified 7 donors observed between one of the genes governing stem and 6 breeding lines w i t h consistency in performance borer resistance and semi-dwarf habit, and also between a resistance gene and flowering d u r a t i o n gene.

Table 3. Promising entries identified against stem borer under A I C R I P 1983-1986. Role of Resistant Varieties in I P M N o . of years w i t h overall promising1 reaction at A l t h o u g h no variety w i t h a high degree of resistance to stem borer damage has been developed, earlier E n t r y Vegetative stage Heading stage breeding programs involving T K M 6 as d o n o r par- Manoharsali 1 3 ent have produced several moderately resistant cul- 2 1 C o 18 tivars, including Sasyasree. Under AICRIP multilo- W 1263 1 1 cational pest management trials, the role of such R Y T 2908 1 - resistant varieties in stem borer management has A R C 6044 1 - been demonstrated. At selected 'hot spot'locations, A R C 5500 - 1 A R C 6215 - 1 use of moderately resistant varieties such as I E T R P 2 1 9 9 - 3 8 - 4 9 - 5 6 - 2 1 1 2815(Sasyasree),IET2812,IET3116,andIET3127 R P 2199-76-42-8 1 1 could reduce pest incidence. Pest damage in moder- R P 2199-115-2 1 1 ately resistant varieties under no protection was R P 2199-201-221 1 1 lower t h a n in the susceptible control variety under R P 2199-84-2 3 - pest management employing need-based protection R P 2068-18-2-9 - 2 (Table 4). Moreover, cultivation of moderately

1. T h e test e n t r y was considered p r o m i s i n g if it h a d less t h a n 2 0 % resistant varieties coupled with need-based applica- deadhearts at vegetative stage or less t h a n 1 0 % w h i t e earheads at tion of pesticides (pest management) increased grain h e a d i n g stage at m o s t of the test l o c a t i o n s . yield.

155 Table 4. Stem borer incidence and grain yield recorded in moderately resistant and susceptible varieties in Pest M a n a g e - ment Trial 1 9 8 4 - 1 9 8 6 .

D a m a g e at

Vegatative stage (% DH) H e a d i n g stage (% W E ) Grain yield (t ha-1) Protec- t i o n 1984 1985 1986 1984 1985 1986 1984 1985 1986 Variety level (3)1 (2) (3) M e a n (3) (2) (3) M e a n (3) (2) (3) M e a n

I E T 3116 PM2 5.3 5.7 6.8 5.9 3.6 3.1 9.7 5.5 4.52 4.67 3.30 4.17 (Moderately NM3 7.9 6.5 9.7 8.0 5.0 4.5 13.7 7.7 3.87 4.04 2.68 3.53 resistant) I E T 3127 PM 4.6 4.7 6.3 5.2 2.8 5.7 11.0 6.5 4.43 4.62 3.32 4.12 (Moderately NM 8.1 8.0 9.6 8.0 4.6 6.3 9.4 6.8 3.86 3.97 2.49 3.44 resistant) I E T 2881 PM 8.9 7.5 14.0 10.1 6.0 10.4 16.2 10.7 4.15 4.17 2.57 3.63 (Susceptible) NM 13.4 17.2 21.7 17.4 10.4 16.8 26.0 17.7 3.50 3.28 1.97 2.92

1 . F i g u r e s i n parentheses are n u m b e r o f test l o c a t i o n s c o n s i d e r e d . 2 . P M = Pest M a n a g e m e n t t h r o u g h need-based pest c o n t r o l . 3 . N M = N o m a n a g e m e n t o f insect pests.

D i s c u s s i o n a n d C o n c l u s i o n s vegetative and heading stage is well-documented. T h o u g h attempts have been made to study the genet- Varietal differences in degree of susceptibility to ics of stem borer resistance (Koshairy et al. 1957, and stem borers have been reported f r o m India as early Dutt et al. 1980), no specific genes conferring resis- as 1937. M o r e systematic field evaluation at C R R l tance have been identified. Thus, it is not clearly d u r i n g the 1950s led to identification of a n u m b e r of known if different moderately resistant donors pos- moderately resistant donors including T K M 6 and sess the same set of genes or if there is any consis- M T U 15 (Israel 1967). Extensive varietal evaluation tency in the makeup of genes governing resistance at programs under A I C R I P d u r i n g the 1960s and different stages of plant growth. Nevertheless, efforts 1970s identified several Assam Rice Collections are being made to accumulate genes f r o m different ( A R C ) accessions w i t h varying levels of resistance moderately resistant donors to develop varieties (Shastry et al. 1971). T h o u g h consistency in perfor- w i t h higher levels of resistance than presently avail- mance of donors like T K M 6 and W 1263 was evi- able (C h o u d h a r y et al. 1984). dent even in recent evaluations reported in this paper, none of the rice germplasm screened so far has displayed a high level of resistance. New donors reported here such as M a n o h a r s a l i , A R C 5500 and R e f e r e n c e s others may serve to supplement future breeding programs. AICRIP (All India Coordinated Rice Improvement Pro- M o s t varietal screening is reported f r o m field stud- ject). 1984. E n t o m o l o g y . Section 3, Pages 1-139 in A n n u a l Report, kharif 1984. New Delhi, India: Indian Council o f ies under natural level of stem borer infestation. Agricultural Research. Such studies have the obvious limitations of n o n u n i - f o r m pest pressure over time and space. This is AICRIP (All India Coordinated Rice Improvement Pro- f u r t h e r complicated by the prevalence of different ject). 1986. E n t o m o l o g y . Pages 2.1-2.142 in Progress complexes of stem borer species at test sites. Differ- report kharif 1986. New Delhi, India: Indian Council o f Agricultural Research. ential reaction of varieties against different species are apparent. F o r instance, d u r i n g the 1984 testing, Choudhary, R . C . , Khush, G.S., and Heinrichs, E.A. 1984. R YT 2908 registered l o w dead heart damage at 5 test Varietal resistance to rice stem borers in Asia. Insect locations but registered the highest damage a m o n g Science and its Application 5(6):447-463. test entries at A l m o r a where the p i n k stem borer D u t t , K . V . L . N . , Seshu, D . V . , and Shastry, S.V.S. 1980. S. inferens predominated (AICRIP 1984). Likewise, Inheritance of resistance to stem borer in rice. Indian J o u r - differential response of varieties and damage at nal of Genetics and Plant Breeding 41:166-171.

156 Heinrichs, E.A. 1980. Varietal resistance to the brown p l a n t hopper and yellow stem borer. Pages 195-217 in Rice improvement in China and Other Asian countries. Los Banos, Laguna, Philippines: International Rice Research Institute.

Israel, P. 1967. Varietal resistance to rice stem borer in I n d i a . Pages 391-403 in M a j o r insect pests of rice plant. B a l t i m o r e , M a r y l a n d , U S A : J o h n H o p k i n s Press.

Koshiary, M . A . , P a n , C . I . , Halt, G.E., Z a i d , I.S.A., Azizi, A . , H i n d i , C , and M a s o u d , M . 1957. A study o n the resistance of rice to stem borer infestations. I n t e r n a t i o n a l Rice C o m m i s s i o n Newsletter 6:23-25.

M a t h u r , K . C . 1983. Losses due to borers in rice. Pages 177-189 in C r o p losses due to insect pests ( R a o , B . H . K . and Murthy, K.S.R.K., eds.). Hyderabad, Andhra Pra- desh, India: Entomological Society of India.

M u n a k a t a , K., and Okamoto, D. 1967. Varietal resistance to rice stem borers in Japan. Pages 419-430 in M a j o r insect pests of rice plant. B a l t i m o r e , U S A : J o h n H o p k i n s Press.

Pathak, M . D . 1967. Varietal resistance to stem borers at I R R I . Pages 405-418 in m a j o r insect pests of rice plant. B a l t i m o r e , M a r y l a n d , U S A : J o h n H o p k i n s Press.

Prasad, G.S.V., Shastry, M . V . S . , Srinivasan, T . E . , and Kalode, M . B . 1984. Inheritance of tolerance to rice stem borer Scirpophaga (Tryporyza) incertulas ( W a l k e r ) and its association with plant habit and maturity period. India n J o u r n a l of A g r i c u l t u r a l Sciences 54(5):352-355.

Shastry, S.V.S., Sharma, S . D . , John, V . T . , and Krish- naiah, K. 1971. N e w sources of resistance to pests and diseases in the Assam rice collections. I n t e r n a t i o n a l Rice C o m m i s s i o n Newsletter 20:1-16.

157

Breeding for Resistance to Stem Borer (Chilo partellus Swinhoe) in Sorghum

B.L. Agrawal1 and S.L. Taneja2

Abstract

Stem borer (Chilo partellus Swinhoe) is the most important pest of sorghum [S o r g h u m bicolor (L.) Moench]. Progress has been made in developing borer-resistant breeding lines with m o d e r - ate yield and acceptable grain quality. Sorghum variety, ICSV 700, has high levels of stem borer resistance across several seasons and locations. Borer resistance is a quantitatively inherited trait governed by additive and nonadditive genes. Epistatic gene effects are more pronounced under artificial borer infestation. Cytoplasmic effects appear to be present.

Introduction appears to be an economic, efficient, and a l o n g - term solution to manage stem borers either alone or S o r g h u m grain yields are generally low (500-800 kg in c o m b i n a t i o n w i t h other methods of c o n t r o l . ha-1) under farmers' conditions in the tropical w o r l d . Research on host-plant resistance to sorghum stem One of the reasons for low yields is crop damage by borers has been done primarily w i t h the spotted stem insect pests. A m o n g the many insect pests w h i c h borer, C. partellus. In this paper, we review the w o r k attack s o r g h u m , stem borers constitute the most done on breeding for resistance to the spotted stem widely distributed and serious group t h r o u g h o u t the borer. w o r l d ( Y o u n g and Teetes 1977, and Seshu Reddy and Davies 1979b). Yield losses due to stem borer can be quite high (80%) in tropical sorghums. These S c r e e n i n g T e c h n i q u e s insects are internal feeders, not m u c h affected by predators and parasites, unfavorable environmental Development of an effective and reliable screening conditions, or insecticides. Host-plant resistance technique that ensures a u n i f o r m and desired level of

1. Plant Breeder, Sorghum Group, Cereals Program, International Crops Research Institute for the Semi-Arid Tropics ( ICRISAT), Patancheru, Andhra Pradesh 502 324, India. 2. Entomologist at the same location.

I C R I S A T Conference Paper no. CP 491. lCRlSAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, I C R I S A T Center, India. Patancheru, A.P. 502 324, India: ICRISAT.

159 insect pressure at the most susceptible stage of the Table 2. Years of effective screening for stem borer resis- crop is the backbone of a host-plant resistance tance in AICSIP trials 1977-86.1 breeding p r o g r a m . These requirements can be met either by selecting a location where the pest occurs Leaf injury Stem tunneling

regularly w i t h adequate severity (hot-spot location) Locations Effective Locations Effective or by testing plant material under artificial infesta- Year tested locations tested locations t i o n w i t h laboratory reared insects. Other agro- 1977 - - 8 1 nomic practices can also be used to increase the 1978 7 2 5 1 insect infestation such as p l a n t i n g time, use of dia- 1979 7 4 8 5 pausing insect population, trap crops, fertilization, 1980 6 3 9 6 and irrigation. 1981 6 4 9 3 A three-step screening methodology was adopted 1982 9 4 10 5 f o r stem borer resistance testing in the A l l India 1983 5 0 7 1 Coordinated S o r g h u m I m p r o v e m e n t Project ( A I C - 1984 - - 6 1 S I P ) ( P r a d h a n et al. 1971). T h e first step was a 1985 4 0 7 1 general screening carried out in single-row plots 1986 9 0 9 5 under natural infestation. Selected materials were 1. Effective screening i m p l i e s a m i n i m u m score of 5 f o r leaf i n j u r y then entered in m u l t i - r o w replicated trials under ( 1 9 scale) a n d 2 5 % t u n n e l i n g o n the susceptible g e n o t y p e . natural infestation. The t h i r d step was c o n f i r m a t i o n Source: AICSIP 1977- 86. of resistance in replicated trials under artificial infes- t a t i o n . I C R I S A T employs a similar methodology (Fig.1) w i t h some m o d i f i c a t i o n , and has w o r k e d w i t h heavy natural infestation at Hisar and artificial infestation at I C R I S A T Center. AICSIP concentrated testing for stem borer resis- Screening at a hot-spot location requires basic tance at Delhi, Udaipur, and Indore, where natural knowledge of insect p o p u l a t i o n dynamics so that stem borer incidence was high. Additional test loca- planting time can be adjusted to ensure that the tions have been added in recent years to record data susceptible stage of the crop coincides w i t h the peak on stem borer infestation on the most susceptible activity period of the insect. For instance, at Hisar, sorghum genotype (Tables 1 and 2). The data i n d i • severe borer infestation has been recorded f o r 10 cate that in any year, sufficient infestation did not years (1977-87) on sorghum planted d u r i n g the first occur at all locations. In 4 out of 7 years, locations f o r t n i g h t of J u l y (10-15 Jul). Early in the project were less than 5 0 % effective in terms of leaf i n j u r y (score of 5 on a 1-9 scale), and in 7 out of 9 years, incidence of stem tunneling was insufficient at all locations. This indicates that the pest attack was Table 1. Testing locations for stem borer resistance in often too low at some of the testing locations a n d / or AICSIP, 1977-86.1 the susceptible stage of the crop did not synchronize L e a f i n j u r y Stem t u n n e l i n g w i t h the peak activity period of the insect. Screening sorghum under artificial infestation has Years Effective Years Effective L o c a t i o n tested years tested years been accomplished by many researchers in I n d i a using laboratory reared insects. Stem borers have D e l h i 8 4 10 6 been reared b o t h on natural food (Singh et al. 1983) I n d o r e 7 4 10 1 and on synthetic diets (Chatterji et al. 1968, D a n g et U d a i p u r 6 0 9 4 al. 1970, Siddiqui et al. 1977, and Seshu Reddy and Navsari 5 4 6 0 Davies 1979b). In AICSIP, laboratory reared insects A k o l a 6 2 9 7 H y d e r a b a d 4 0 5 2 have either been released as first-instar larvae (Singh D h a r w a d 6 1 9 5 et al. 1983) or as blackhead egg masses in the leaf C o i m b a t o r e 4 0 4 3 whorls (Jotwani 1978). R a h u r i 5 2 6 0 ICRISAT Center's artificial rearing laboratory P a r b h a n i 1 0 7 2 supports the screening of 2-3 ha of s o r g h u m each

1. E f f e c t i v e s c r e e n i n g i m p l i e s a m i n i m u m score of 5 f o r leaf i n j u r y season by raising enough first-instar larvae to p r o - ( 1 - 9 scale) a n d 2 5 % t u n n e l i n g o n t h e susceptible g e n o t y p e . vide an infestation rate of 5-7 insects per i n d i v i d u a l S o u r c e : A I C I P 1 9 7 7 - 8 6 . plant. Details of this rearing method, field infesta-

160 S 2 testing F5s F6s • resistance • resistance • agronomic • agronomic

Resistance

Preliminary testing • germplasm

A g r o n o m i c

S, testing Advance testing • resistance • replicated Observation nursery • testing: • nonreplicated -natural -artificial

Multilocational C o m b i n e d Half-sib testing testing Preliminary • agronomic • replicated Varietal • natural and Trial (CPVT) • artificial • replicated

F1s, 3-way Population International C o m b i n e d 4-way and • recombine testing Advance Varietal B crosses T r i a l ( C A V T ) • replicated • multilocational

International Sorghum Varietal Trial (ISVAT)

Strong, stable and promising

• ICRISAT Center breeders • national • registration

F i g u r e 1 . S c r e e n i n g a n d b r e e d i n g f o r insect-pest resistance.

161 t i o n , and evaluation f o r stem borer resistance has B u t a n i (1949). Pant et al. (1961) and S w a r u p and been described by Taneja and Leuschner (1985). Chaugale (1962) reported certain sorghum varieties to be relatively less-damaged by the stem borer t h a n others. A systematic screening of the world sorghum S e l e c t i o n C r i t e r i a collection f o r resistance to stem borers was started in 1962, in India, under the cooperative efforts of the S y m p t o m s of stem borer attack in s o r g h u m are leaf Accelerated H y b r i d S o r g h u m Project, I n d i a n C o u n - i n j u r y , tunneling of stem and peduncle, and dead- cil of Agriculture and Research (ICAR), the Ento- heart f o r m a t i o n . Each of these symptoms is not mology Division of the Indian Agricultural Research necessarily related to grain yield loss. A l t h o u g h leaf Institute (IARI), and the Rockefeller Foundation i n j u r y is the first indication of borer attack, it has no (Singh et al. 1968, Pradhan et al. 1971, and J o t w a n i clear relationship w i t h yield loss (Singh et al. 1983). 1978). This w o r k has been continued by A I C S I P and Leaf i n j u r y score varies over time because the plant ICRISAT. recovers by producing new leaves. However, Singh General screening of sorghum germplasm for and Sajjan (1982) observed a positive relationship stem borer resistance was carried out under natural between leaf i n j u r y score and grain yield loss in infestation at D e l h i f r o m 1964 to 1969. A t o t a l of maize. 8557 lines were screened, and 1375 lines were Stem tunneling by borers is also not related to selected f o r further testing (Table 3). Evaluation of grain yield reduction in s o r g h u m (Singh et al. 1983, these lines was done on the basis of deadheart Pathak and Olela 1983, and Taneja and Leuschner f o r m a t i o n . 1985). Stem and peduncle damage can be critical, Retesting of selected germplasm accessions was however, under t w o situations: (1) if tunneling carried out at D e l h i , Udaipur, and Pune d u r i n g results in breakage of stem or peduncle; and (2) if 1966-76 and a number of accessions were selected tunneling interferes w i t h plant nutrient supplies by f o r c o n f i r m a t i o n of resistance (Table 4). The resis- destroying the vascular system of the stalk. These tance in selected genotypes was confirmed by a r t i f i - t w o situations depend on the critical stage of the cial infestation at Delhi, Udaipur, Indore, and Kan- crop at time of infestation, and borer density. pur (Table 5). The most critical damage by the stem borer, which At ICRISAT, stem borer resistance work began in results in significant grain yield loss and l o w plant 1979 using artificial infestation (Seshu Reddy and stand, is the f o r m a t i o n of deadhearts. Taneja and Davies 1979). Later on, testing of the material also Leuschner (1985) observed highly significant and began at Hisar under natural infestation. Out of negative relationship between number of deadhearts nearly 16000 germplasm accessions tested over sev- and grain yield of sorghum (r = -0.9). Singh et al. eral seasons, 72 genotypes have been f o u n d to be (1968) indicated that as a parameter of stem borer resistant (Table 6). Most of these sources are of attack, the percentage of deadheart was the most I n d i a n o r i g i n ; however, some genotypes are f r o m stable criterion for differentiating degrees of resistance. Researchers argue strongly that resistance screen- i n g should be based m a i n l y on deadhearts, while stem tunneling and leaf i n j u r y can be subsidiary Table 3. Screening of sorghum germplasm for stem borer criteria. In A I C S I P the deadheart parameter was resistance under natural infestation. used as a prime criterion f o r the evaluation of Incidence on Accessions sorghum material f o r stem borer resistance u n t i l Selection susceptible 1969. O n l y leaf i n j u r y and stem tunneling are being Year Screened Selected criteria1 c o n t r o l used as selection criteria at the present time. At 1964 3492 I C R I S A T , evaluations are done on the basis of 1965 461 507 DH 80% (32-100%) deadheart incidence, with leaf injury and stem tun• 1967 890 74 L I , S T S T = 5 8 % neling as secondary criteria. 1968 2906 794 L I , D H , D H = 3 2 % ST S T = 3 0 % 1969 808 0 LI, D H Identification of Resistant Sources 1 . S e l e c t i o n c r i t e r i a : L I = leaf i n j u r y , D H = d e a d h e a r t s , S T = s t e m T h e earliest report on sorghum cultivars resistant to t u n n e l i n g . spotted stem borer (C. partellus) is by Trehan and S o u r c e : S i n g h e t a l . 1968, a n d P r a d h a n e t a l . 1971.

162 Table 4. Screening of sorghum genotypes for stem borer resistance under natural infestation in replicated trials, A I C S I P 1966-76

Incidence on Accessions Selection susceptible Year Screened Selected criteria1 c o n t r o l P r o m i s i n g genotypes

1966 488 57 L I , D H , S T - I S Nos. 1034, 1099, 1151, 1499, 5479

1967 104 73 L I , D H , S T D H - 3 8 % IS N o s . 1034, 1044, S T - 5 0 % 1087, 1115, 1137, 1151 3950, 4522, 4569, 4776, 4912, 4994, 5030

1968 91 42 L I , D H , S T D H - 3 0 % IS Nos. 1044, 5030 S T - 2 8 % 5606, 5615, 5656

1969 151 40 L I , S T S T - 7 2 % I S Nos. 1 1 5 1 , 4 2 4 6 , 4 3 0 7 , 4339, 4868, 4870, 5072, 5599, 5629, 5653, 5662

100 16 L I , D H D H - 2 9 % IS Nos. 1005, 1019, 1509, 1522, 1594,4522, 4780, 4793, 4797, 4833, 4866, 4870, 4897, 4912, 5615, 5701

1973 28 13 L I , S T S T - 2 3 % J M L - 2 , A K L - 5 , Gangapuri, NCL-3, PCL-3, Aispuri

1976 23 23 L I , S T - V Z M - 2 B , P 151, S P V 61

1. Selection c r i t e r i a : LI = leaf i n j u r y , DH = deadhearts, ST = stem t u n n e l i n g . S o u r c e : S i n g h et a l . 1968, P r a d h a n et a l . 1971, a n d J o t w a n i 1978.

East Germany, Nigeria, Pakistan, Sudan, Uganda, Genetics of Resistance U S A , Yemen A r a b Republic, and Zimbabwe. Sta- bility analysis, of 61 resistant genotypes tested over Knowledge of genetics of resistance and tolerance is six seasons indicated that the most stable resistant prerequisite to determining appropriate breeding lines were IS 5470, IS 5604, IS 8320, and IS 18573 methods to be used in developing insect-resistant (Taneja and Leuschner 1985). cultivars. There is limited i n f o r m a t i o n available, however, on inheritance of resistance to s o r g h u m stem borers. Resistance to spotted stem borer C. partellus, measured in terms of leaf feeding injury, percentage deadhearts, and stem tunneling is Resistance Mechanisms polygenic (Rana and M u r t y 1971, K u l k a r n i and a n d A s s o c i a t e d F a c t o r s M u r t y 1981, Pathak and Olela 1983, Pathak 1983, Rana et al. 1984, Hagi 1984, and Pathak 1985). Rana Knowledge of resistance mechanisms and associated and M u r t y (1971) indicated that the inheritance factors in donor parents is important in transferring patterns of primary (leaf injury) and secondary resistance into elite cultivars. The role of various (stem tunneling) damage were different. Resistance mechanisms and morphological and chemical fac- to primary damage was predominantly controlled tors has been emphasized by several workers. A by additive and additive x additive gene effects while detailed review of this has been covered by Taneja additive and nonadditive gene effects were i m p o r - and Woodhead in their paper Mechanisms of Stem tant for secondary damage. Height and maturity Borer Resistance in Sorghum (these proceedings). traits were also f o u n d to be associated w i t h different

163 Table 5. Confirmation of stem borer resistance in sorghum lines under artificial infestation, AICSIP 1966-1975.

Incidence on N u m b e r o f lines Selection susceptible Year Screened Selected criteria1 c o n t r o l M o s t p r o m i s i n g lines

1966 5 5 DH - IS N o s . 1034, 1099, 1151, 1499,5479

1968 59 36 L I , D H , S T DH- 18% IS N o s . 1099, 1115, ST- 3 4 % 1458,3967,4118,4283, 4316, 4522, 4 6 5 1 , 4776, 4780,4897,5115, 5469, 5613, 5656

17 7 L I , D H , S T DH- 9 % IS Nos. 1044, 1115, 1151, ST- 3 3 % 4764, 4776, 4994, 5030

1969 20 6 LI, S T S T - 7 6 % IS Nos. 1056,4552,4651, 4747, 4782, 5470

1972 8 7 LI, S T S T - 8 7 % IS Nos. 4424, 4689, 4827, 4841,4875,4934,5031

1973 98 25 LI, S T S T - 6 5 % IS N o s . 2122, 4329, 4799, 5251,6046,6101,6119

1975 25 12 LI, S T S T - 3 7 % 12 6 LI, S T G I B , B P 53, A i s p u r i , N a g - B , S P V 16 and R 147B

1. S e l e c t i o n o u t l i n e : LI = leaf i n j u r y , DH = d e a d h c a r t s , ST = stem tunneling. S o u r c e : P r a d h a n et a l . 1971; J o t w a n i 1978.

types of damage. In a diallel cross analysis in F2 and general c o m b i n i n g ability ( G C A) effects over gener-

F 3 generations, K u l k a r n i a n d M u r t y (1981) reported ations indicated that at least one parent should be a that resistance to percentage deadhearts is governed good combiner in breeding for stem borer resistance. by both additive and nonadditive types of gene In another diallel cross analysis, Pathak and Olela actions, but predominantly by additive genes. The (1983) showed that resistance to deadhearts (prim-

Table 6. Sources of resistance to sorghum stem borer identified by I C R I S A T , 1979-86.

O r i g i n I S N u m b e r

India 1044, 1082, 1119, 2195, 2205, 2375, 2376, 4273, 4546, 4637, 4756, 4757, 4776, 4881, 4981, 5075, 5253, 5429, 5469, 5470, 5480, 5538, 5566, 5 5 7 1 , 5585, 5604, 5619, 5622, 8320, 13100, 17742, 17745, 17747, 17750, 17948, 17966, 18333, 18366, 18662, 18677, 21969, 22039, 22091,22145,23411, Nigeria 7224, 18573, 18577, 18578, 18579, 18580, 18584, 18585 USA 2122, 2123, 2146, 2168, 2269, 10711, 20643 S u d a n 2263,2291,2309,2312,22507 U g a n d a 8 8 1 1 , 13674 E.Germany 24027 E t h i o p i a 18551 Pakistan 9608 YAR 23962 Z i m b a b w e 12308

S o u r c e : T a n e j a a n d L e u s c h n e r 1985.

164 ary damage) is governed predominantly by additive Table 7. Most productive borer resistant sources and genes. They also f o u n d that inheritance patterns of their promising derivatives. p r i m a r y and secondary damage are different. B o t h resistance and tolerance mechanisms f o r stem borer Resistant Other resistance exist in sorghum. source parent Promising derivatives

H a g i (1984) studied the genetics of resistance (per- B P 53 IS 2954 Selection nos. 165, 169, 174, centage deadhearts) to spotted stem borer under 177,300,364,384,434,446,468, natural and artificial infestations, and f o u n d differ- D nos. 124, 167, 168, 172, 175, 244, ent patterns of resistance under these t w o situations. 259, 350, 358, 365, 366, 367, 609, M a j o r gene effects (additive and dominant) were DU nos. 98, 135,245,293, found to be contributing under natural infestations P nos. 108, 1 5 1 , 2 3 5 , U 376 IS 84 while epistatic effects (additive x additive, additive x Selection no. 602 IS 3691 D U 2 9 1 , U 369 d o m i n a n t , and d o m i n a n t x dominant) were predom- C K 60 B E 302, U nos. 37, 218, 35, 373 inantly contributing under artificial infestation, IS 3954 E 303 where the expression of major gene effects is masked. A i s p u r i IS 3922 Selection nos. 829, 835, D 832 In t u r n , his studies indicated that the ovipositional M 35-1 IS 539 D U 19 nonpreference mechanism is controlled by major I S 531 U 83 gene effects, while antibiosis is influenced by epis- IS 4906 C K 6 0 A P 37 tatic gene effects. The epistatic gene effects were IS 5837 C K 6 0 A P 82 f o u n d unstable over environments. IS 10327 C K 6 0 A P 90

Pathak (1985) reported that susceptibility is d o m - S o u r c e : A I C S I P 1972-85. inant over resistance in susceptible x resistant (SxR) and susceptible x tolerant (SxT) crosses, while resistance was dominant over susceptibility in the tolerant x resistant ( T x R ) cross. Both resistance and genes f r o m different sources. To meet this objective, tolerance mechanisms were found to be operating a population breeding approach was chosen. A and independently inherited. Estimates of low herit- sorghum population resistant to shoot pests, (shoot ability, genetic coefficient of variability, and ex- fly and stem borer) has been developed using ms3 pected genetic advance indicated the usefulness of and ms7 male-sterility genes. So far, a total of 175 recurrent selection to simultaneously improve the genotypes have been fed into this populations (85 level of stem borer resistance, tolerance, and yield in sorghum.

Table 8. Stem borer resistant sources utilized in AICSI P.

B r e e d i n g f o r Resistance Resistant source Promising varieties/hybrids

C S V 5, S P V nos. 14, 58, 80, 9 6 , 99, Breeding for stem borer resistance started in 1966 in A i s p u r i and its derivatives 101, 102, 104, 105, 107, 108, 110, I n d i a , when a number of resistant parents were 115, 168,265,270,271,374,378, included in the breeding program (Pradhan et al. 475, 513, 516, 716, 727, 743, 1971). Since then a number of identified sources of 744, C S H 7R resistance have been utilized by crossing them mostly w i t h agronomically elite susceptible parents. IS 3541 C S V 4, S P V nos. 60, 104, 122, 126, (CS 3541) 245, 292, 297, 303, 312, 346, A list of promising derivatives and their parents is 351,354,371,386,741 given in Table 7. A borer-resistant parent, BP 53, has produced a number of promising derivatives, par- M 35-1 C S V 7 R , S P V nos. 19, 270, 364, 440, ticularly when crossed w i t h IS 2954. Other good ( I S 1054) 510, 727 resistant sources have been A i s p u r i , M 35-1 and G M 1-5 S P V nos. 9, 33, 34, 183, 268 K a r a d L o c a l . Stem borer resistant sources have also K a r a d Local C S V nos. 2, 6, S P V nos. 8, 13, 17 been utilized in developing high-yielding varieties and hybrids in A I C S I P (Table 8). B P 53 (IS 1055) CSV 3, 26, 70, 513, 688

One of the objectives of the Stem Borer Resistance P D 3-1 C S H 8 R P r o g r a m initiated at I C R I S A T was to strengthen Source: AICSIP 1975-86. the sources of resistance by accumulating diverse

165 stem borer resistant sources and their derivatives, 76 shoot fly resistant sources and their derivatives, and 24 14 elite genotypes). A f t e r six cycles of r a n d o m mat-

ing under borer-infested conditions, this population P e d i g r e e has shown good improvement for agronomic fea- 20 derivatives tures and resistance. The shoot pests resistant p o p u - l a t i o n is being advanced by using (S ) cyclic recur- 2 P o p u l a t i o n rent selection as outlined in Figure 2. 16 derivatives A comparison of 135 fertile derivatives (S2) of the shoot pest p o p u l a t i o n and 130 advanced progenies f r o m pedigree breeding was made f o r stem borer 12 resistance at I C R I S A T Center under artificial infes- t a t i o n , and at Hisar under natural infestation, during the 1986 rainy season. In general, the p o p u l a t i o n 8 derivatives showed better levels of resistance under b o t h types of infestation compared w i t h progenies derived t h r o u g h pedigree breeding (Fig.3). The pop- 4 u l a t i o n derivatives showed a good level of borer resistance, 6%, compared w i t h only 0.6% resistance of the pedigree progenies. 0 Transfer of resistance into i m p r o v e d genotypes, H i s a r P a t a n c h e r u H i s a r + P a t a n c h e r u initiated t h r o u g h the pedigree breeding approach L o c a t i o n s has utilized a number of resistant sources (Table 9). M o s t productive are IS 1082, IS 3962, IS 5604, and F i g u r e 3 . P e r f o r m a n c e o f pedigree a n d p o p u l a t i o n lS 5622. The most p r o m i s i n g derivatives are I C S V derivatives against stem borer.

S e a s o n S t e p s Number Activity Location

S u m m e r P o p u l a t i o n 1 R a n d o m m a t i n g I C R I S A T C e n t e r

R a i n y H a l f - s i b s 2 0 0 0 A g r o n o m i c I C R I S A T C e n t e r e v a l u a t i o n

P o s t r a i n y S 1 p r o g e n i e s 1000 Evaluation ICRISAT Center - b o r e r - s h o o t f l y

R a i n y / S 2 p r o g e n i e s 2 5 0 E v a l u a t i o n p o s t r a i n y - b o r e r - n a t u r a l H a r y a n a A g r i c u l t u r a l U n i v e r s i t y , H i s a r - a r t i f i c i a l I C R I S A T C e n t e r

Select 25-30 Shoot fly ICRISAT Center best p r o g e n i e s agronomic ICRISAT Center

F i g u r e 2 . S c h e m e f o r r e c u r r e n t s e l e c t i o n .

1 6 6 Table 9. Stem borer resistant sources and their promising scrutiny, particularly as any correlation may influ- derivatives, utilized at I C R I S A T Center. ence future breeding strategies for borer resistance.

Resistant source Promising derivatives

IS 1082 PS 14413, PB 10791, PB 12446 Conclusions and Recommendations

IS 2312 PS 19338, PB 12693 The effectiveness of a host-plant resistance breeding IS 3962 PS 18601, PS 18822, PB 12611, program largely depends on the development of a P B 12631 reliable screening technique, reliable criteria for IS 5604 PS 18527, PS 19336, PS 27623 measuring resistance, identification of stable sources PB 10365, PB 12040, PB 12497, of resistance, knowledge of the inheritance of resis- PB 12687, PB 12689 tance per se, the resistance mechanisms, and finally

IS 5622 PS 14454, PS 19295, PS 19663, the selection of breeding procedures to incorporate PS 21113, PS 30768, PS 30769, resistance into agronomically superior backgrounds. PS 31376, PB 10337, PB 10445, A l t h o u g h considerable w o r k on host-plant resis- PB 10446 tance to stem borer has been accomplished in I n d i a and elsewhere, there is still a scope f o r further IS 13681 PB 12049, PB 12050 improvement. Intensified efforts are needed in the S h o o t pest PB 12339, PB 12342, PB 12346, following areas: p o p u l a t i o n PB 12380, PB 12387, PB 12413

• Natural borer infestations at specific locations should receive a thorough examination of p o p u - lation dynamics, planting time, use of overwin- 700, I C S V 701, I C S V 825, I C S V 826, 1CSV 827, tering population, fertilizers, and other factors I C S V 828, and I C S V 829 (Table 10). affecting these populations. Experience over the years has shown that there is • Feasibility of artificial infestation should be con- very little correlation between selections made for sidered by national programs according to the stem borer resistance under natural and artificial facilities and support available. conditions. This may be due to the differential • Determine breeding should be carried out under expression of resistance mechanisms in these t w o natural or artificial borer infestations, or under types of infestations. Some mechanism(s) may not both types. be operating under both types of infestations. Sim- • Deadhearts should be given prime consideration ilar observations were made by Haji (1984) in his as a selection criterion for resistant types. Stem genetic studies conducted in relation to natural and tunneling and leaf injury should be used as artificial infestations. This apparent dichotomy needs secondary parameters. • Tolerance should be considered as a factor in breeding for borer resistance. • Cultivars with multiple resistance should be devel- Table 10. Performance of improved lines for stem borer oped according to regional needs. resistance. • M o r e genetic information needs to be generated

Resistance index1 on individual resistance factors/mechanisms/ resistance. Line N a t u r a l A r t i f i c i a l • Resistant parents need to be developed to use in 1CSV 700 0.50 1.250 the further development of resistant hybrids. I C S V 701 0.65 0.625 I C S V 825 1.05 1.320 I C S V 826 0.90 0.625 I C S V 827 0.13 1.380 R e f e r e n c e s I C S V 828 0.94 0.710 I C S V 829 0.96 0.700 AICSIP (All India Coordinated Sorghum Improvement Project) 1971-86. Progress reports of the All India Coo r d i - % of dead hearts in a p a r t i c u l a r line 1. Resistance i n d e x = nated Sorghum Improvement Project, Entomology Sec- % of dead hearts in resistant c o n t r o l tion, Indian Council of Agricultural Research and ( I S 2205) Cooperating Agencies. New Delhi, India: AICSIP.

167 Chatterji, S.M., Siddiqui, K.H. Panwar, V.P.S., Sharm a , Siddiqui, K.H., Sarup, P., Panwar, V.P.S., and Marwa h a , G.C., and Y o u n g , W . R . 1968. R e a r i n g of the maize stem K . K . 1977. Evaluation of base-ingredients to formulate borer, Chilo zonellus Swinhoe on artificial diet. Indian a r t i f i c i a l diets f o r the mass rearing of Chilo partellus ( S w i n - J o u r n a l o f E n t o m o l o g y 30:8-12. hoe). Journal of Entomological Research 1:117-131.

D a n g , K., A n a n d , M . , and Jotwani, M . G . 1970. A simple Singh, B.U., Rana, B.S., Reddy, B.B., and Rao, N.G.P. i m p r o v e d diet f o r mass rearing of s o r g h u m stem borer, 1983. Host plant resistance to stalk-borer, Chilo partellus Chilo zonellus (Swinhoe). Indian Journal of Entomology Swin., in sorghum. Insect Science and its Application 32:130-133. 4(!-2):407-413.

H a g i , H . M . 1984. Gene affects f o r resistance to stem b o r e r Singh, J., and Sajjan, S.S. 1982. Losses in maize yield due (Chilo partellus S w i n h o e ) in s o r g h u m {Sorghum bicolor to different damage grades (19 scale) caused by maize ( L . ) M o e n c h ) . M.Sc. thesis, A n d h r a Pradesh A g r i c u l t u r a l borer, Chilo partellus (Swinhoe). Indian Journal of Ento- University, Hyderabad, Andhra Pradesh, India. m o l o g y 44:41-48.

Jotwani, M . G . 1978. Investigations on insect pests of Singh, S.R., Vedamoorthy, G., Thobbi, V.V., Jotwani, sorghum and millets with special reference to host plant M.G., Young, W.R., Balan, J.S., Srivastava, K.P., resistance, final technical report (1972-1977). IARI Sandhu, G.S., and Krishnananda, N. 1968. Resistance to Research Bulletin (New Series) no.2. New Delhi, India: stem borer, Chilo zonellus ( S w i n h o e ) and stem fly Atherig- Indian Agricultural Research Institute. ona varia soccata R o n d . in w o r l d s o r g h u m collection in I n d i a . M e m o i r s o f the E n t o m o l o g i c a l Society o f I n d i a Kulkarni, N., and M u r t y , K . N . 1981. S t e m borer resistance 7:1-79. i n s o r g h u m . I n d i a n J o u r n a l o f Genetics a n d Plant Breeding 41:167-169. Swarup, V., and Chaugale, D.S. 1962. A p r e l i m i n a r y study on resistance to stem borer, Chilo zonellus ( S w i n h o e ) infes- Pant, N.C., Pathak, M . D . , a n d Pant J . C . 1961. Resistance t a t i o n on s o r g h u m , Sorghum vulgare Pers. Current to Chilo zonellus Swin. in different host plants. Indian Science 31:163-164. J o u r n a l o f E n t o m o l o g y 23:126-136. Taneja, S.L., and Leuschner, K. 1985. M e t h o d s of rearing, Pathak, R.S., and Olela, J.C. 1983. Genetics of host plant infestation, and evaluation for Chilo partellus resistance in resistance in f o o d crops w i t h special reference to s o r g h u m sorghum. Pages 175-188 in Proceedings of the Interna- stem-borers. Insect Science and its Application t i o n a l S o r g h u m E n t o m o l o g y W o r k s h o p , 15-21 J u l 1984, 4 ( 1 - 2 ) : 127-134. College Station, Texas, USA. Patancheru, A.P. 502 324, Pathak, R.S. 1983. Genetics of s o r g h u m resistance to stem India: International Crops Research Institute for the S e m i - borers. Page 729 in Abstracts of c o n t r i b u t e d papers of the Arid Tropics. International Congress of Genetics, 12-21 Dec 1983, New Trehan, K.N., and Butani, D.K. 1949. Notes on life history, D e l h i , I n d i a . Pt.2. N e w D e l h i , I n d i a : O x f o r d a n d I B H b i o n o m i c s a n d c o n t r o l of Chilo zonellus ( S w i n h o e ) in Publishing C o . Bombay Province. Indian Journal of Entomology Pathak, R . S . 1985. Genetic v a r i a t i o n of stem borer resis- 11:47-59. tance a n d tolerance in three s o r g h u m crosses. Insect Young, W.R., and Teetes, G.L. 1977. S o r g h u m e n t o m o l - Science and its Application 6(3):359-364. ogy. Annual Review of Entomology 22:193-213. Pradhan, S. et a l . 1971. Investigations on insect pests of sorghum and millets: final technical report (1965-70). N e w Delhi, India: Indian Agricultural Research Institute.

R a n a , B.S., and M u r t y , B.R. 1971. Genetic analysis of resistance to stem borer in s o r g h u m . I n d i a n J o u r n a l of Genetics and Plant Breeding 31:521-529.

Rana, B.S., Singh, B.U., Rao, V.J.M., Reddy, B.B., and R a o , N . G . P . 1984. Inheritance of stem borer resistance in s o r g h u m . I n d i a n J o u r n a l o f Genetics a n d P l an t Breeding 44(1):7-14.

Seshu Reddy, K . V . , and Davies, J.C. 1979b. A new m e d i u m f o r mass rearing of s o r g h u m stem borer, Chilo partellus S w i n h o e ( L e p i d o p t e r a : Pyralidae) a n d its use in resistance screening. Indian Journal of Plant Protectio n 6:48-55.

168 Breeding Maize and Sorghum for Resistance to the European Corn Borer

W . D . Guthrie'

Abstract

Resistance in maize, Zea mays L., to leaf feeding by first-generation European corn borers (ECB), Ostrinia nubilalis Hubner, is conditioned by at least eight genes. Resistance to sheath-collar feeding by second-generation ECB is conditioned by at least seven genes. Reciprocal transloca• tion studies showed that at least 12 of the possible 20 chromosome arms, contributing a minimum of 13 genes, are in volved in resistance; only 2 or 3 of the 12 chromosome arms are in common for genes resistant to the two ECB generations. Thus, resistance to the ECB is conditioned by two different mechanisms. This number of genes rules out the possibility of using a backcross procedure to transfer resistance to susceptible maize genotypes. A recurrent selection breeding technique was used to develop genotypes of maize resistant to leaf feeding by first-generation ECB, resistant to sheath-collar feeding by second-generation ECB, and to develop genotypes with resistance for the whole life of the plant.

Introduction and (5) plant breeding techniques. This approach has been employed by both the public and private A successful host-plant resistant project is depend• sectors in the U S A and approximately 10 other ent u p o n : (1) an efficient insect-rearing technique; countries in breeding maize, Zea mays L., for resis- (2) efficient artificial infestation of crop plants; (3) tance to the European corn borer ( E C B ) , Ostrinia efficient evaluation of plants; (4) genetic techniques; nubilalis Hubner.

1. Supervisory Research Entomologist, Corn Insects Research Unit, United States Department of Agriculture, Agricultural Research Service ( U S D A / A R S ) , and Department of Entomology, Iowa State University, Ames and Ankeny, IA 50021, USA.

ICRISAT (International Crops Research Institute for the Semi-Arid Tropics). 1989. International Workshop on Sorghum Stem Borers, 17-20 Nov 1987, ICRISAT Center. India. Patancheru, A.P. 502 324, India: ICRISAT.

169 E g g P r o d u c t i o n tion ECB, maize is in the whorl stage of plant development. M o s t larvae feed on leaf tissue in the moist The use of wheat germ m a r k e d the advent of practi• area deep in the w h o r l f o r several days after egg cal artificial diets f o r rearing plant-feeding L e p i d o p - hatch. Most first-generation larval mortality occurs tera. This is the single most significant breakthrough during the first few days after egg hatch. Resistance in breeding maize f o r resistance to the E C B . In 1987, to first-generation ECB on maize is, therefore, leaf- researchers in the private and public sectors in the feeding resistance; i.e., high antibiosis against first U S A and several foreign countries produced 70 m i l • and second instars. lion ECB egg masses (2 billion eggs) for host-plant Breeding methods used to develop crop cultivars resistance research. Using the meridic diet tech• resistant to insects are determined by t w o factors: (1) nique, seven times as many egg masses were p r o • mode of reproduction in the crop species; and (2) the duced in 1987 t h a n were produced by the United k i n d of gene action that conditions resistance in the States Department of Agriculture (10 m i l l i o n masses) host-plant to the insect. over a 33-year period (1932-65) w i t h the old tech• M a n y studies have been made to determine the nique (Guthrie 1987). genetic basis of resistance (Guthrie and Russell In

press). Segregation of F2 and backcross generations of a susceptible (M 14) x resistant (MSI) cross indi- P l a n t E v a l u a t i o n cates that at least three gene pairs are involved in leaf-feeding resistance, with at least partial pheno- In first-generation E C B resistance studies, maize typic dominance of susceptibility. In a B14 (suscept- and sorghum plants are infested w i t h egg masses or ible) x N32 (resistant) cross, one or two genes for larvae d u r i n g the m i d w h o r l stage of plant develop• leaf-feeding resistance by first-generation borers ment. Relative degree of resistance (antibiosis) is were indicated on the basis of individual plant segre- measured by rating the leaf-feeding damage on gation in F2 and in backcrosses. In another suscepti- plants (individual-plant or plot basis) on a scale of ble (WF9) x resistant (gl7 V17) cross, segregation of 1-9, where 1 = no damage to leaf tissue and 9 = F 2 and backcross populations showed that resist- extensive damage. Leaf-feeding damage ratings are ance of gl7 V1 7 was conditioned by a single dominant made 3 weeks after egg hatch. gene. The resistant gene was linked with gl7 V1 7 genes In second-generation ECB resistance studies, of the resistant parent with crossover frequencies maize plants are infested w i t h egg masses or larvae estimated at 31-37%. It was concluded from the ease (sorghum plants are infested w i t h egg masses) d u r i n g of transferring resistance by backcrossing with selec- anthesis. Antibiosis in maize is scored by rating the t i o n in the improvement of inbred line Oh45 that sheath-collar feeding damage on plants (plot basis) leaf-feeding resistance to first-generation borers was on a scale of 1-9, where 1 = no damage, and 9 = simply inherited. But in a study of the use of test extensive damage. Sheath-collar feeding ratings are crosses in breeding for resistance, segregation in a made 45-60 days after egg hatch. Genotypes w i t h 24-line synthetic cultivar, as measured by the net ratings of 7-9 are discarded. Cavity counts (cm of variance, diminished after each selfing, while a sig- damage in stalks) may be used to detect differences nificant residue of segregation remained in the f i f t h a m o n g genotypes w i t h ratings of 1-6. Damage (cm) selfed generation. If there was an average of one in peduncles and heads may be used to detect differ• effectual heterozygous locus in the S5, theoretically, ences among genotypes of sorghum. there should have been 25 or at least 32 effectual Genotypes of maize are evaluated for tolerance by heterozygous loci five generations back in the S0. determining the percentage of broken stalks as an To determine the type of gene action involved in index of stalk strength, and by determining percen• resistance to leaf feeding by first-generation borers, tage of dropped ears as an index of shank strength F , F , and selfed backcross populations of C131A (Guthrie and Barry In press). 2 3 (resistant) x B37 (susceptible) were used along with

individual F2 plants of ( C I 31A x B37) x Cl 31 A, and Genetics and Breeding for Resistance individual F2 plants of (Cl 31A x B37) x B37. Most of the genetic variance was of the additive type, al- to First-Generation E C B t h o u g h a p o r t i o n of the genetic variance was of the dominant type. Maize Reciprocal translocations were used in identifying D u r i n g the period of egg deposition by first-genera- chromosome arms involved in resistance to E C B .

170 The inbred C131A has genes f o r resistance to leaf inbreds (SC213) rated resistant to sheath-collar feed- feeding by first-generation borers on the short arms ing (antibiosis) by second-generation ECB. of chromosomes one, t w o , and four, and on the long arms of chromosomes f o u r and six. Inbred B49 has genes f o r resistance on these chromosome arms S o r g h u m (possibly allelic to those of C131A) plus an additional gene for resistance on the long arm of c h r o m - Most E C B larvae feed on leaf tissue in the moist area osome eight. Leaf-feeding resistance factors differ- deep in the w h o r l of sorghum, Sorghum b i c o l o r(L) entiating the inbred line A411 f r o m the susceptible Moench, for 9 days after egg hatch. M o s t first- line A 3 4 4 are associated w i t h one gene on the 3L generation ECB larval mortality occurs d u r i n g the chromosome, one gene on the 4L chromosome, and first few days after egg hatch. Resistance to first- probably another on the 5L chromosome. generation E C B on s o r g h u m , as in maize, is there- An A c - D s mutable system (jumping genes) was fore leaf-feeding resistance, i.e., high antibiosis evaluated f o r inducing resistance to leaf feeding by against first and second instars. first-generation E C B in t w o susceptible inbred lines D u r i n g the 1960s, several sorghum cutlivars were (Oh28 and W F 9 ) of dent maize. No mutants were evaluated under a low level of artificial ECB infesta- f o u n d a m o n g 40000 plants evaluated. We did not tion (75 eggs per plant). D u r i n g 1981-83, 208 prove that this biotech technique will or will not sorghum hybrids were evaluated under a high level cause mutations for corn borer resistance; perhaps a of artificial ECB infestation (750 eggs per plant). All m i l l i o n , 2 m i l l i o n , or 10 m i l l i o n plants would have to sorghum genotypes were resistant to leaf feeding by be evaluated. We believe that the Ac-Ds mutable first-generation ECB. The leaves on sorghum had system, however, is not a practical tool for maize pinholes, indicating that some larvae fed f o r o n l y a breeders because the maize genotypes being im- short time on leaf tissue. proved may be obsolete before a mutant can be Because all sorghum genotypes are resistant to f o u n d . leaf feeding by first-generation ECB, the type of gene The development of genotypes resistant to the action and number of genes c o n d i t i o n i n g resistance E C B has been in progress for more than 60 years. are impossible to determine. Resistance to leaf feeding by first-generation E C B has been easy to f i n d , whereas frequency of genes in maize f o r resistance to sheath-collar feeding by Genetics a n d B r e e d i n g f o r R e s i s t a n c e second-generation borers is low. t o S e c o n d G e n e r a t i o n E C B Open-pollinated cultivars were the direct source material f o r most of the inbred lines developed f r o m M a i z e 1930-40. D u r i n g the 1940s and 1950s, inbred lines w i t h a satisfactory degree of resistance were ex- D u r i n g the period of egg deposition by second- tracted f r o m special crosses (second-cycle breeding). generation E C B , maize is in various stages of anthe- D u r i n g the 1960s-80s, a recurrent selection tech- sis. Most larvae feed on sheath-collar tissue for sev- nique was used to improve resistance in breeding eral days after egg hatch. Resistance in maize, populations f r o m which resistant lines may be therefore, is resistance to sheath-collar feeding. developed. A generation-mean analysis was used to deter-

In a study of S1 lines recurrent selection for leaf- mine the genetic basis of sheath-collar feeding resis- feeding resistance by first-generation E C B in five tance by second-generation borers. Nine p o p u l a -

synthetic cultivars of maize, t w o cycles of selection tions were studied: P1, P2, F1, F2, F3, BC1, BC2 , and were sufficient to shift the frequencies of resistant selfed progenies of both backcrosses. The data i n d i - genes to a high level in all cultivars. Three cycles of cated no simple genetic basis of resistance and sug- selection produced essentially borer-resistant lines. gested that high resistance to a second-generation In I o w a , 34 of the 99 most widely used public infestation may be the result of the cumulative effect inbred lines of maize rated highly resistant, resistant, of an unknown number of loci. Additive genetic or intermediate in resistance to leaf feeding (antibio- effects were predominant in conditioning resistance, sis) by first-generation E C B . In the United States in but dominance was significant in all crosses. 1975, about 7.4 m i l l i o n ha of maize were planted to Inbred B52 (highly resistant to sheath-collar feed- hybrids whose pedigrees contained at least one of the ing by second-generation borers) contains a gene or resistant or intermediate lines. O n l y one of the 99 genes on the long arms of chromosomes one, t w o ,

171 f o u r , and eight and on the short arms of c h r o m o - feeding by first-generation E C B , the backcross me- somes one, three, and five. The frequency of genes t h o d was not successful w h e n the recurrent parent f o r resistance to sheath-collar feeding by second- was susceptible. The desired genotype could not be generation E C B is very low. O n l y one inbred line, identified in the segregating generations. W h e n B52, and three maize composite populations have a more t h a n t w o backcrosses were used, the needed good degree of resistance. level of resistance was lost. The level of resistance could be increased, however, by intermating among resistant plants in progeny of the first or second Sorghum backcross. Reciprocal translocation studies also showed that D u r i n g the period of egg deposition by second- only 3 of the 12 chromosome arms are in c o m m o n generation E C B , sorghum is in various stages of for genes resistant to the two ECB generations. Eva- anthesis. M o s t larvae feed on sheath-collar tissue f o r luation of S1 lines showed near-zero correlation 35 days after egg hatch. Resistance in sorghum as in between the t w o E C B generations f o r resistance. maize, therefore, is resistance to sheath-collar feed- T h u s , resistance to E C B is conditioned by t w o d i f - ing. S o r g h u m genotypes vary in degree of resistance- ferent mechanisms. susceptibility when an infestation occurs d u r i n g Ten inbred lines were selected to develop a syn- anthesis. Some genotypes are highly susceptible, thetic cultivar, designated BS9, specifically for S1 however, E C B larvae rarely enter sorghum stalks recurrent selection for ECB resistance throughout below the peduncle, so only peduncles and heads are the whole life of the plant. The 10 lines were: B49, damaged. In constrast, on susceptible genotypes of B50, B52, B54, B55, B57, B68, C131A, Mol7, and maize infested d u r i n g anthesis, E C B larvae tunnel SD10. These lines vary in their resistance to the t w o throughout the whole plant. generations of E C B . The genetic basis of sheath-collar feeding resis- The objective in the BS9 improvement p r o g r a m tance in sorghum is not k n o w n . A f u l l set of t r i s o m - was to evaluate 300 S, lines in each cycle (ca 10% of ies is available f o r locating chromosome arms in- the best S1 were recombined to start the next cycle) in volved in insect resistance, but the trisomic genetic three replications using separate experiments for the stocks are difficult to m a i n t a i n . A f u l l set of recipro- two generations under heavy artificial infestation. cal translocations (20 are needed) is not yet available W h e n BS9(CB)C4 (four cycles of recurrent selec- in sorghum f o r d e t e r m i n i n g the number of genes tion) was released to the h y b r i d seed industry in 1982 conditioning resistance to second-generation E C B . it marked a significant event in host-plant resistance

Three cycles of S1 line recurrent selection in t w o investigations. It was the first C o r n Belt ( m i d - sorghum populations increased resistance to second- western U n i t e d States) synthetic specifically devel- generation borers. As in maize, polygenes probably oped and released w i t h resistance to E C B for the condition resistance to second-generation E C B in whole life of the plant. To determine the efficacy of sorghum. S, recurrent selection f o r resistance to the t w o generations of E C B , the base p o p u l a t i o n ( C O ) and four succeeding cycles (C1, C2, C3,and C4) of selec- Combining Resistance in Maize to t i o n in BS9 were evaluated b o t h f o r E C B resistance F i r s t - a n d S e c o n d - G e n e r a t i o n E C B and correlated effects of agronomic traits. Each population (CO, CI, C2, C3, C4) was crossed with P o p u l a t i o n improvement programs are needed to f o u r C o r n Belt inbreds (test cross parents) selected develop genotypes resistant t h r o u g h o u t the life of on the basis of their reactions to the t w o generations the maize plant because genotypes of maize, resis- of E C B : B73 is susceptible to b o t h generations; B75 tant to first-generation E C B , are usually susceptible is highly resistant to first and susceptible to second to second-generation E C B . generations, B52 has intermediate resistance to first Results from reciprocal translocation studies generation, and is highly resistant to second genera- showed that at least 12 of the possible 20 c h r o m o - t i o n ; and B86 is highly resistant to b o t h generations. some arms, c o n t r i b u t i n g a m i n i m u m of 13 genes, are Significant increases were f o u n d f r o m B S 9 C O to involved in resistance to E C B . This number of genes BS9 ( C B ) C4 f o r resistance to first generation (leaf rules out the possibility of using a backcross proce- feeding), second generation (sheath-collar feeding), dure to transfer resistance to susceptible maize geno- and stalk tunneling (cavity counts). First-generation types. In many efforts to breed f o r resistance to leaf leaf-feeding damage decreased f r o m 3.6 in CO to 2.7

172 in C4 for cycles and f r o m 3.9 in CO to 3.2 in C4, for displayed resistance to both ECB generations. cycles in test crosses. Second-generation sheath- collar feeding damage decreased f r o m 6.4 in CO to 4.4 in C4 for cycles and f r o m 5.6 in CO to 4.7 in C4, C h e m i c a l Basis o f E C B R e s i s t a n c e f o r cycles in test crosses. Second-generation damage in stalks (one cavity = 2.5 cm) decreased f r o m 8.4 in Maize CO to 3.3 in C4 f o r cycles and f r o m 7.4 in CO to 4.9 in C4, for cycles in test crosses. DIMBOA (2,4-dihydroxy-7- methoxy- 1,4- benzoxazin- The increase in resistance in populations of BS9 3-one) is a chemical factor present in resistant geno- reduced yield losses under artificial infestations of types of maize in the w h o r l stage of development. A E C B , but the reduction was not sufficient to com- simple inbreeding and selection technique f o r D I M - pensate for the loss in yield potential that occurred B O A (in a cross of a susceptible and resistant inbred as a correlated effect f r o m selection f o r E C B resis- line) and a recurrent selection technique can be used tance. Reduction in the grain yield f r o m BS9CO to to increase levels of D I M B O A f o r resistance to leaf BS9(CB)C4 under no artificial infestation was esti- feeding by first-generation E C B . Selection only on mated to be 8.4% caused by changes in gene fre- the basis of D I M B O A , however, may cause the quency due to selection and 18.8% caused by eventual loss of other E C B resistance factors in inbreeding depression due to drift. M o s t of the yield maize breeding populations. Furthermore, DIM- reduction, therefore, was caused by a r a n d o m fixa- B O A is not a factor in resistance of genotypes of t i o n of heterozygous loci, and the yield reduction maize to second-generation ECB because sheath- may have been increased because of linkages to collar tissue contains very little D I M B O A . alleles of other traits under direct and indirect selection. S, recurrent selection, therefore, was effective in Sorghum increasing resistance throughout the life of the maize plant, but unfavorable responses in other agronomic D I M B O A is not a chemical factor in the resistance traits, particularly in grain yield, suggest that the to leaf feeding by first-generation E C B . Research in selection criteria for E C B resistance should include 1949 implicated cyanogenetic ( H C N ) as a resistance yield. factor. If H C N is, however, a resistance factor, it is Because of limitations of resources for replicated effective at very low concentrations because geno- yield trials and the importance of p o p u l a t i o n size to types of sorghum containing low levels of H C N were reduce d r i f t , an S1 recurrent selection p r o g r a m as resistant as genotypes containing high levels of w o u l d be the most desirable method to implement. HCN. A l t h o u g h this w o u l d require an extra year in tem- perate zones, selection can be conducted in t w o seasons. The S1 lines could be evaluated for first- and D i s c u s s i o n a n d C o n c l u s i o n s second-generation ECB resistance, anthesis date, and plant height in one or t w o replications to elimi- A host-plant resistance project is of value even if it nate the most undesirable lines. These traits could only prevents the release of extremely susceptible then be evaluated again in a smaller p o p u l a t i o n of S2 germplasm. For example, in our 14 0 0 0 - 2 0 000-plot lines, in addition to evaluations for yield in repli- nursery ( C o r n Insect Research Unit), each year a few cated trials. lines are so highly susceptible to E C B that the insect Inbred B86 was developed by selecting and self- kills every plant. This type of material is culled pollinating through several generations in progeny immediately. of a single cross, B52 x Oh43, under high artificial Hopefully, some of the genetic engineering tech- infestations of both generations of E C B . The inbred niques w i l l be useful in breeding maize f o r resistance contributes resistance to first-generation ECB (from to insects. Improvement in crops w i t h multiple gene the Oh43 parent) and resistance to second-generation traits, however, is a building process based on step- E C B ( f r o m the B52 parent) in single-cross hybrids. wise accumulation of genes w i t h favorable additive B86 was the first inbred of C o r n Belt origin k n o w n to effects. At present, the only k n o w n way to accumu- combine into one genotype good resistance to the late favorable genes for multiple gene traits is by insect f o r the life of the plant. Recently, t w o other selecting over several sexual generations involving publicly released inbreds, SC213 and D E 8 1 1 , have genetic recombination. In sexually produced crops,

173 the most efficient breeding methods to accumulate insects feeding on B.t. toxin-transformed plants favorable genes w i l l necessarily play the largest role develop resistance to the B.t. toxin? Will single-cross in plant breeding. hybrids be resistant if o n l y one inbred line contains Resistance to leaf feeding by first-generation E C B the B.t. t o x i n gene, or w i l l b o t h inbreds have to is conditioned by at least eight genes, and resistance contain the gene? to sheath-collar feeding by second-generation E C B Endophytes (microorganisms that live within a is conditioned by at least seven genes. Recurrent plant) may be useful in t r a n s p o r t i n g the B. t. t o x i n to selection breeding methodology has been successful all plant parts. For example, Crops Genetics Inter- in developing genotypes of maize w i t h resistance to n a t i o n a l C o r p o r a t i o n has used biotechnology to b o t h generations of borers. It is n o t k n o w n if genetic m o d i f y the genetics of selected endophytes to p r o - engineering techniques will be as successful or faster duce biological crop protectants and g r o w t h en- t h a n recurrent selection in breeding genotypes of hancers. Tools of biotechnology include transfor- maize resistant to insects. m a t i o n (the process o f i n t r o d u c i n g foreign D N A Genetic engineering technology may be used to into an organism), recombinant DNA (new sequen- insert a genetically engineered Bacillus thuringiensis ces o f D N A f o r m e d b y chemically recombining d i f - (B.t.) t o x i n gene i n t o the plant itself, m a k i n g the ferent segments of DNA), protoplast fusion (forma- plant inherently resistant to insects. The level of gene tion of a hybrid cell by joining two different cells expression must be high enough so that an insect f r o m w h i c h the cell walls have been removed), and feeding on the plant tissue consumes a lethal dose of mutagenesis (the deliberate creation, utilizing physi- the t o x i n before the plant incurs unacceptable levels cal, chemical, or biological agents of a mutant). The of damage ( K i r s c h b a u m 1985). c o m p a n y expects to use recombinant D N A and McGaughey (1985) reported that, in tests w i t h mutagenesis f o r its crop protectant and g r o w t h B. thuringiensis f o r the c o n t r o l of the Indianmeal enhancer products. Recombinant DNA technology m o t h , Plodia interpunctella (Hubner), two genera- requires that the company develop genetic trans- tions of exposure resulted in 30-fold resistance and f o r m a t i o n systems, a range of promoters (a D N A that 15 generations of exposure resulted in 100-fold sequence that controls gene expression), and an resistance of the insect to the pathogen. At present, it array of appropriate vectors (the agent used to carry is not k n o w n if insects feeding on B.t. t o x i n - new D N A i n t o a cell) f o r its endophytes and insert transformed plants w i l l also develop resistance. It is bacterial genes into the endophytes. The company k n o w n that genotypes of maize developed (by has discovered an endophyte f o r maize, has refined o r t h o d o x breeding methodology) f o r resistance to recombinant D N A tools, and has acquired a gene insects such as the E C B , have not developed insect p r o d u c i n g a t o x i n active against the E C B . The insec- biotypes that can overcome the resistance ( p r o b a b l y ticide gene is f r o m a strain of B. thuringiensis. because resistance is multigenic). M o l e c u l a r biologists have successfully engineered A s s u m i n g that a B.t. t o x i n gene can be inserted the B.t. gene into a nonendophytic bacterium and i n t o maize plants rendering susceptible genotypes have demonstrated activity against the E C B . They resistant to insects, many questions w i l l have to be are evaluating a range of promoters isolated f r o m answered before the technique can be used in breed- the maize endophyte f o r a b i l i t y to drive the expres- i n g maize f o r resistance to insects. F o r example, w i l l sion of the B. t. gene. They have inserted the B. t. gene the B.t t o x i n gene express itself in all plant parts? i n t o the endophyte and are currently evaluating the Whorl leaves contain factors conditioning resistance engineered bacteria for insecticidal output, genetic to leaf feeding by first-generation E C B . Sheath- stability, and levels of colonization in laboratory collar tissue contains factors c o n d i t i o n i n g resistance and greenhouse trials. In summary, C r o p Genetics t o second-generation E C B . The D I M B O A gene o r International Corporation is developing a family of genes are expressed at a high level in m i d w h o r l genetically engineered microbial pesticides, which leaves of some genotypes of maize but at a very l o w can be inoculated into seeds and plants. These level in sheath-collar tissue. Thus, D I M B O A is a pesticide-producing microorganisms are designed to chemical factor c o n d i t i o n i n g resistance to leaf feed- reside and f u n c t i o n in a plant's vascular system and ing by first-generation E C B , but is not a factor in provide benefits f o r the life of the plant. Because the c o n d i t i o n i n g resistance to sheath-collar feeding by endophytic delivery system functions internally, the second-generaton E C B . F o r the B. t. t o x i n gene to be plant w i l l protect the products f r o m outside envi- effective t h r o u g h o u t the life of the plant, it w i l l have ronmental forces that degrade externally applied to be expressed in several plant parts. W i l l maize biologicals and chemicals. The system should be cost

174 effective because single application of minute dosages are anticipated to achieve and sustain potency f o r the life of the plant ( A n o n y m o u s 1987).

Acknowledgements

This report is a jo i n t contribution of the C o r n Insects Research U n i t , United States Department of A g r i - culture, Agricultural Research Service, and Journal Paper N o . J-12719 of the I o w a Agriculture and H o m e Economics Experiment Station, Ames, I o w a 50011, and A n k e n y , I o w a 50021. Project No.2513.

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McGaughey, H. 1985. Insect resistance to the biological insecticide Bacillus thuringiensis. Science 229:193-195.

175 D i s c u s s i o n similar studies not done on B. fusca, the main stem borer in Africa? Vidyabhushnam: W h a t is the nature of inheritance Seshu Reddy: Some w o r k on the resistance of of resistance to rice stem borer? sorghum to B. fusca is being done at I C I P E under Kalode: In one of the crosses studied in rice by natural infestation. Investigations under artificial Prasad et al. in 1984, Phalguna x T K M 6, resistance infestation are hindered because of lack of adequate is governed by d o m i n a n t genes and 1 d o m i n a n t techniques for the mass rearing of B. fusca. inhibitory gene at heading stage. Lavigne: If resistant hybrids of corn are so widely Vidyabhushnam: While screening the breeding planted in the U S A and give such good control of the material for stem borer, what precautions are taken first b r o o d of E C B , w h y is the second b r o o d infesta- to c o n t r o l shoot fly? If the screening is done under tion such a problem? This question relates to areas of conditions free of shoot fly, the chances of natural A f r i c a where sorghum is double-cropped. If we con- infestation by stem borer are also likely to be low. It trol the first generation with resistant lines, will we w o u l d be desirable to have an approach c o m b i n i n g still have a problem with the second generation of the t w o pests together. stem borers? Agrawal: Shoot fly incidence is avoided by adjusting Guthrie: The biological capacity of the E C B is great. sowing dates. Regarding screening under natural A large second generation can develop f r o m a small infestation at Hisar, planting in the first fortnight of first generation population if climatic conditions are July resulted in very little shoot fly incidence. favorable. Screening under artificial infestation avoids the Lukefahr: In hot-spot evaluation tests, what percen- problem. Efforts are already being made to combine tage of the time do y o u obtain results that are not resistance to b o t h shoot fly and stem borer. comparable to artificial infestation? Also, how are Seshu Reddy: In answer to Dr V i d y a Bhushanam's hot spots selected? question, Dr A g r a w a l indicated IS 1082,2122,2312, Taneja: There is at least 50% correspondence between 5604, and 5622 as materials c o n t r i b u t i n g to stem the results obtained at hot spots and under artificial borer resistance. A l l these entries are also resistant to infestations. H o t spots are selected on the basis of sorghum shoot fly. I am happy that D r s A g r a w a l severity and regularity of the pest incidence at a and Taneja have been t r y i n g to incorporate resis• particular location. tance sources of shoot fly and stem borer into h i g h - yielding cultivars. In fact this is an excellent approach where t w o major pests have been considered. Kaiser Jamil: A m o n g the several strains of Bacillus thruriongiensis, w h i c h particular strain was utilized for incorporation into the seeds? H o w was this done? Guthrie: These are trade secrets. Seshu Reddy: In A f r i c a , Chilo, Busseola, Sesamia and Eldana have all been f o u n d feeding on the grains. Does the corn borer bore into maize cobs? Guthrie: Yes, the c o r n borer bores into maize cobs. M u k u r u : Dr G u t h r i e , y o u indicated in your presen• tation that there is resistance to first generation E C B in hybrids g r o w n in the U S A , but not to second generatione E C B . Y o u also indicated that by using recurrent selection y o u have been able to increase resistance to both first and second generation E C B . W h y is it then that second generation resistance has not been incorporated into commercial hybrids in the U S A using recurrent selection. Guthrie: We have recently received genotypes w i t h resistance to b o t h borer generations, so we have not had enough time to get these genotypes into hybrids. D a k o u o D o n a : A lot of studies are undertaken on C. partellus at I C R I S A T and at I C I P E . W h y are

176 Plenary Session

Recommendations dispersal and ovipositional preferences), the physiology of diapause, and population dynamics. In accordance w i t h the objectives of the workshop Preparation of reviews will indicate where further participants were divided into two groups to research i s needed t o p r o v i d e a d d i t i o n a l deliberate on issues arising f r o m presentations and information. discussions and to draw-up recommendations. These recommendations were presented at a plenary session d u r i n g which each point was discussed, Yield Loss Assessment modified where necessary, and then approved. The recommendations are presented under two major Evidence on crop losses directly attributable to sections: Biology and C o n t r o l ; and Host plant sorghum stem borers is conflicting. The assessment Resistance and Breeding for Resistance. of losses is difficult especially on farmers' fields, but there are important indirect effects of borer attack through interactions with stress factors, especially Biology and Control drought and sorghum midge. There is a need to determine situations in which stem borers are Pest surveys restricting sorghum production now, and are likely to restrict it in the future. The need for surveys of sorghum stem borers on farmers' fields was recognized. These w i l l require careful planning to obtain essential i n f o rma t i o n Control Measures using standardized procedures that will allow repeatability and comparision of data across Chemical Control. Chemical control will continue locations. There is a need for: species identification; to be used in some circumstances but seems unlikely the farmers' perception of infestation levels, and to be used extensively on sorghum by small-scale losses; and identification of control measures farmers. In India, some further research is needed on employed in different countries. The need f o r techniques of application and economic thresholds. logistic support w i t h transport and other facilities in some areas was noted. Biological Control. The importance of endemic complexes of predators, parasitoids and pathogens in limiting stem borer infestations is not f u l l y Diagnostic Aids understood. It was stressed that the beneficial effects of these complexes should not be lost. Conservation Accurate identification of pest species is essential in and augmentation of natural enemies merit further surveys and other w o r k , and it was suggested that study and a better understanding of the role of illustrated diagnostic data sheets should be pathogens is needed. produced by the Commonwealth Institute of Entomology (CIE) for the main stem borer species. Cultural Methods. It was agreed that the choice and implementation of cultural methods of c o n t r o l depend on local circumstances and action must be Biology, Ecology, Physiology, and Behavior taken at that level.

It is recognized that m u c h published a n d unpublished information is already available but there is a need to prepare critical reviews as a basis Host-plant Resistance and Breeding for further w o r k . This would best be done by reviewing information that relates to each of the for Resistance major species (Chilo partellus, Busseola fusca, Sesamia calamistis, S. cretica, S. inferens, Eldana 1. Host-plant resistance is a viable o p t i o n to stem saccharina, Acigona ignefusalis, and Diatraea b o r e r m a n a g e m e n t . I n a d d i t i o n t o t h e saccharalis). Emphasis should be placed on factors development of resistant cultivars it will help in affecting the distribution of pest species, behavioral avoiding the release of super-susceptible studies of adults and larvae (including adult cultivars.

179 2. Rearing procedures and facilities for Chilo are Integrated Pest Management (IPM) adequate at l C R I S A T , and are in progress at regional centers but not in some of the national Stem borer research should have as its ultimate programs. Rearing facilities f o r other stem borer objective the development of IPM strategies for species should be initiated. Hotspots should be farming systems, talcing into account the f a r m i n g identified for screening under natural infestation. communities in particular regions and subregions. 3 . I n f e s t a t i o n p r o c e d u r e s a r e a d e q u a t e l y Cultural methods and host plant resistance were established for Chilo. Infestation should be done recognized as the major viable components in I P M . at 2 and 4 weeks after emergence. Correlations should be worked out between early and late infestations w i t h regard to leaf feeding and Training dead heart f o r m a t i o n . 4. Evaluation for stem borer resistance should be Apart from general training at lCRISAT Center carried out f o r the following parameters: (lC) specific training at IC or in national programs should be organized in the f o r m of training • Leaf feeding at 7 days after artificial infestation workshops. Such training should be conducted at and 3 and 6 weeks after emergence under regular intervals if they are to have long-term and natural infestation. sustained impact on national programs. • Dead heart counts should be taken 15 days after artificial infestation and 4 and 6 weeks after crop emergence under natural infestations. • Panicle damage should be evaluated at Group discussions on Resistance maturity. Screening Methodology and Yield • Stem tunneling counts should be taken only in Loss Assessments held at 1500-1630 fodder sorghums and for economic threshold studies. on 20 Nov 1987

5. Biology and behavior of stem borers should be F o l l o w i n g the recommendations in the plenary studied on resistant genotypes. Resistance session, a special group meeting was held to discuss mechanisms and associated factors should be and streamline the procedures/methodologies to be worked out. used in resistance screening and yield loss 6. Genetics of resistance on each evaluating assessments. The following is a summary of the parameters should be reexamined through discussions. generation mean and diallel analysis, with emphasis on leaf feeding and dead hearts. 7. Utilize genetic i n f o r m a t i o n f o r d e c i d i n g Screening Methodology appropriate breeding schemes. Recurrent selection is presently being used in breeding for 1. Damage rating for leaf injury should be scored Chilo resistance at I C R l S A T and also in f r o m : 0 to 9 combining Chilo resistance w i t h resistance to 0 = I m m u n e other insect pests. This will help to accumulate 1-2 = Highly resistant r e s i s t a n t genes i n t o c o m m o n g e n e t i c 3-4 = Resistant background(s) for multiple resistance. 5-6 = Intermediate 8. Screening of wild sorghums for stem borer 7-9 = Susceptible resistance should be done to identify strong Develop a diagramatic rating scale showing resistant sources. different scores for u n i f o r m i t y in evaluation. 9. The above recommendations are mainly for Prepare slides for use in workshops and seminars Chilo partellus; for other borer species they for national programs. should be modified wherever necessary. 2. For evaluation under natural infestations, 10. Since I C I P E is planning a stem borer workshop damage rating should be based on infested plants w i t h i n the next three years, the progress made on only. stem borer research should be reviewed d u r i n g 3. Deadhearts should be considered a parameter as that workshop. indicated in the recommendations i.e., deadheart

180 count 2 weeks after artificial infestation, and 4 and 6 weeks after crop emergence in case of natural infestation. 4. Panicle damage should be evaluated by conducting a series of experiments at various locations, with infestations at various crop g r o w t h stages (boot leaf, postboot leaf and panicle emergence). The following parameters should be noted: bored panicles and chaffy panicles/unproductive panicles.

Yield Loss Assessments

1. Pest surveys should be conducted in India for the major pests of sorghum. Their frequencies of occurrence and severity of attack should be monitored along geographical zones. 2. Yield loss assessment trials should be conducted at specific locations and the f o l l o w i n g methodologies should be used: • insecticide protected and unprotected trials • artificial infestation • paired plant analyses of infested and uninfested plants 3. The relationships between insect infestation and actual yield losses should be worked out. 4. A realistic and comprehensive estimation of insect related losses under farmers' situations should be conducted.

181 D i s c u s s i o n Saxena: Pheromones for monitoring C. partellus are not satisfactory and require further studies. H o w - Harris: A l t h o u g h considerable i n f o r m a t i o n is avail- ever, B. fusca populations can be monitored effec- able on stem borer research, there is no central rep- tively using pheromones. Some cultural practices ository f o r these documents. C A B can assist in c o m - also have the potential for reducing stem borer dam- piling existing information. However, informal publi- age and may be mentioned in recommendations. cations f r o m national programs w i l l need to be Harris: Cultural control has a potential, and varies added to the i n f o r m a t i o n base. This d o c u m e n t a t i o n according to local practices. There may even be need effort can be taken up as a cooperative effort and f o r proper legislation to take up such practices over C A B can be a contributor. We have an i n f o r m a t i o n large areas. However, we have not gone to that level base dating back to 1972. I C R I S A T should serve as yet. a focal p o i n t f o r collection and dissemination of Vidyabhushnam: Seasonal abundance and off-sea- i n f o r m a t i o n . We should start w i t h Busseola and son carryover studies should be emphasized. then move to Chilo and Acigona. A m i n : In l P M , wh a t w o u l d y o u like to have as a Kanwar: The C A B offer is welcome. The existing major component? i n f o r m a t i o n can be made available in a few weeks. Harris: Host-plant resistance. The missing i n f o r m a t i o n f r o m national programs Kanwar: People in national programs should i n d i - can be added to it. In case of species present in cate the type of t r a i n i n g required, and the scientists A f r i c a , possibly agencies such as O D A may also be and technicians should be identified w h o might ready to help. benefit from participation in such training. Lavinge: We should have an i n f o r m a t i o n base and Nwanze: Apparently, equal weight is being sug- then decide what is to be done. Areas of research gested for different parameters f o r measuring insect should be identified and duplication should be damage. W h a t is the justification? avoided. Wiseman: Leaf damage should reflect plant resis• Kanwar: Recommendations quite often remain on tance. Stem tunneling has been suggested for forage paper, we should identify the people to undertake sorghums. Possibly, different types of resistance this documentation activity. I recommend that Dr may operate at different stages. Harris o f C A B and D r Saxena o f I C I P E should Guthrie: It may t u r n out that we can infest at one prepare a critical review, w i t h support f r o m I C R I - stage only, if there is a good correlation in plant S A T . A decision can be made later whether this resistance across stages. However, resistance fac- material should be published or mimeographed for tors, e.g., DIMBOA concentration in maize changes distribution. w i t h plant age. de Wet: As we move the discussion f o r w a r d I w o u l d Kanwar: A committee should suggest ways of eva- like to have y o u consider the question, are borers luating materials for resistance. We should develop a important? W h a t are incidence and damage levels? n e t w o r k of people w o r k i n g f o r a c o m m o n cause and Sithole: We have not worked on losses in Z i m b a b w e , agree on a c o m m o n program. but infestation may be as high as 70%. A c t u a l losses Lavinge: A subcommittee should discuss what para- are not k n o w n . meters should be measured for host-plant resistance Lavinge: In Somalia, 100% of sorghum fields may in stem borer research. show infestation, and 6 - 1 0 % of the plants show Nwanze: We shall meet in the afternoon. dead hearts. Seshu Reddy: We should also look into multiple pest Nwanze: In West A f r i c a , infestation may go up to resistance. Those interested in H P R should come 100%, but actual losses may only be 5%. Various together and collaborative arrangements should be estimates show 10-15% actual losses. made. Seshu Reddy: In Eastern A f r i c a we have conducted de Wet: We are planning to have a network of testing a number of surveys. A b o u t 10-75% losses are material for resistance to insects, diseases, and other recorded due to all pests. Elaborate techniques are traits. difficult to use on farmers* fields. T i m e of infestation Nwanze: We have started multiple pest resistance determines the actual losses due to insects. w o r k , and the same is reflected in recommendations. Wiseman: If y o u have a proper chemical control de Wet: I am n o w fully convinced that research on check, y o u can estimate the associated losses w h i c h stem borers is an essential component of cereals may be attributable to all pests. Specific experiments improvement program. may have to be set up f o r this purpose. Kanwar: One of the i m p o r t a n t contributions of

182 H P R is to stop the release of supersusceptible cultivars in the absence of cultivars with high levels of borer resistance. ICRlSAT's Cereal Entomology P r o g r a m should come up with proposals for discussion at the p r o g r a m level on future research on stem borers. It is time to revise our projects and make the necessary changes. Resistance to other insects should also be incorporated. The future technology should be modern, economical, and viable. Management of pests should be our aim, and needs to be cost effective. We should also think of millets. I C R I S A T , I C l P E , and other institutions should w o r k together and even justify and sponsor common workshops. O u r approach should be interdisciplinary in nature. Entomologists and breeders should go hand in hand to make fast progress in H PR and pest management.

183

Participants

O. Ajayi V.P. Deshpande Entomologist University of Agricultural Sciences Institute for Agricultural Research Extension Education U n i t A h m e d Bello University College of Agriculture P M B 1044 Dharwad 580 005 Z a r i a Karnataka Nigeria India

C. Asanga A . N . Duale Cereal Entomologist Entomologist Institute of A g r o n o m i c Research National Sorghum Improvement Project B P 44 P O Box 2971 Dschang Mogadishu Republic of Cameroon Somalia

M . Ashok B.H. Gadalla Research Scholar Lecturer in Entomology Central University Department of Crop Protection Hyderabad 500 030 Faculty of Agricultural Sciences I n d i a Gezira University M e d a n i M . Betbeder-Matibet PO Box 20 Sudan Service Entomologie Institut de Recherches Agronomiques W.D. Guthrie Tropicales et des Cultures C o r n Insects Research Unit Vivieres ( I R A T ) United States Department of Agriculture, Centre de Recherches C I R A D Agricultural Research Service Avenue du V a l de M o n t f e r r a n d ( U S D A / A R S ) , and BP 5035 Department of Entomology 34032 Montpellier cedex Iowa State University France Ames and Ankeny IA 50021 R . D . Chundurwar USA Senior Scientist Department of Entomology Hussein M a o Haji Marathwada Agricultural University Coordinator National Sorghum Parbhani 431402 Improvement Project Maharashtra P O Box 2971 I n d i a Mogadishu Somalia D . Dakouo Entomologiste K M . Harris Institut d'Etudes et de Director Recherches Agricoles ( I N E R A ) Commonwealth Agricultural Station de Recherches Bureau International (CABI) Agronomiques de Saria Institute of Entomology B P 10 56, Queen's Gate K o u d o u g o u L o n d o n S W 7 5JR B u r k i n a Faso UK

185 J. Kabisa R. Reyes Agricultural Research Institute Coordinator, Sorghum Program llonga Centro Nacional de Tecnologia Private M a i l Bag Kilosa Agricola ( C E N T A ) Tanzania L a Libertad A p a r t a d o Postal 885 M B . Kalode San Salvador Senior Entomologist and Head El Salvador Directorate of Rice Research ( D R R ) Rajendranagar K.N. Saxena Hyderabad 500 030 Program Leader A n d h r a Pradesh C r o p Pests P r o g r a m India International Centre of Insect Physiology and Ecology ( I C I P E ) S. Kearl PO Box 30772 Editor N a i r o b i International Programs Kenya University of F l o r i d a 3028 M c C a r t y H a l l K.V. Seshu Reddy Gainesville Senior Research Scientist F L 32611 International Centre of Insect USA Physiology and Ecology ( I C I P E ) P O Box 30 R. Lavigne M b i t a Team Leader Kenya Bay Region Agricultural Development Project ( B P H D P ) Shankar Dayal Mogadishu Research Scholar Somalia Department of Entomology Andhra Pradesh Agricultural University G.P. Lodhi Hyderabad 500 030 Senior S o r g h u m Breeder India Department of Plant Breeding Haryana Agricultural University L.S. Sharma Hisar 125 004 Head India Department of Entomology Sukhadia University Prem Kishore Udaipur 313 001 Entomologist Rajasthan D i v i s i o n o f E n t o m o l o g y India Indian A g r i c u l t u r a l Research Institute ( I A R I ) New D e l h i 110 012 Shashi Bhalla I n d i a Entomologist Germplasm Evaluation D i v i s i o n P. Raja Sekhar National Bureau of Plant Genetic Research Scholar Resources ( N B P G R ) Department o f E n t o m o l o g y New D e l h i 110 012 Andhra Pradesh Agricultural University India Hyderabad 500 030 I n d i a

186 C.B. Shinde R.V. Vidyabhushnam Senior Entomologist (Sorghum) Project Coordinator College of Agriculture All India Coordinated Sorghum Indore 452 001 Improvement Project (AICSIP) M a d h y a Pradesh Rajendranagar I n d i a Hyderabad 500 030 India B . U . Singh Scientist S-2 B.R. Wiseman I n d i a n Agricultural Research United States Department of Agriculture, Institute ( I A R I ) Agricultural Research Service ( U S D A / A R S ) Regional Station Insect Biology and Population Rajendranagar Management Research Laboratory Hyderabad 500 030 P O Box 748 A n d h r a Pradesh T i f t o n I n d i a GA 31793-0748 USA S.P. Singh Assistant Entomologist S. Woodhead Department of Entomology Overseas Development Natural Haryana Agricultural University Resources Institute ( O D N R I ) Hisar 125 004 College House H a r y a n a Wrights Lane I n d i a L o n d o n W8 5SJ UK S.Z. Sithole M i n i s t r y of Lands, Agriculture, I C R I S A T Center and R u r a l Resettlement Department of Research and Administration Specialist Services L.D. Swindale, Director General Plant Protection Research Institute J.S. Kanwar, Deputy Director General P O B o x 8100 Causeway Cereals Program Harare Z i m b a b w e J.M.J, de Wet, Program Director

R . P . Srivastava Sorghum Group: Assistant Professor S.Z. Mukuru, Principal Plant Breeder Department of Entomology K.F. Nwanze, Principal Cereals Entomologist G o v i n d Ballabh Pant University of B.L. Agrawal, Plant Breeder Agriculture and Technology S.L. Taneja, Entomologist Pantnagar 263 145 H.C. Sharma, Entomologist U t t a r Pradesh P.K. Vaidya, Plant Breeder I n d i a Legumes Program A . N . Verma Groundnut group: Professor and Head J.A. Wightman, Principal Entomologist Department of Entomology P.W. A m i n , Coordinator and Entomologist, Haryana Agricultural University LEGOFTEN Hisar 125 004 G.V. Ranga Rao, Entomologist H a r y a n a I n d i a Pulses Group: S.S. Lateef, Pulse Entomologist

187 Resource Management Program

R.A.E. Mueller, Principal Economist, Economics G r o u p C.S. Pawar, Entomologist, A g r o n o m y group

Genetic Resources Unit

K.E. Prasada R a o , Sr Botanist

I C R I S A T Sahelian Center, Niger

M.J. Lukefahr, Principal Millet Entomologist, Pearl Millet Improvement P r o g r a m

S A D C C Regional Sorghum and Millet Improvement Program, Zimbabwe

K. Leuschner, Principal Cereals Entomologist

188 ICRISAT

International Crops Research Institute for the Semi-Arid Tropics Patancheru, Andhra Pradesh 502 324, India

ISBN 92-9066-145-3 ICR 88-0054