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Canada •

INTEGRATED PEST MANAGEMENT APPROACH FOR THE SORGHUM SHOOT FLY, ATHERIGONA SOCCATA RONDANI (DIPTERA: MUSCIDAE), IN BURKINA FASO

by

Joanny O. Zongo

A thesis submitted to the Faculty of Graduate Studies and Research • in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph.D.)

Department of Entomology McGill University Montréal, Québec Canada August 1992

~ cJoanny O. Zongo Nationallibrary Bibliothèque nationale of Canada du Canada Acquisitions and Direction des acquisitions el Bibliographie Services Branch des services bibliograplliques 395 Wellington Street 395. rue Wellington ûnawa. Ontario Onawa (Ontario) K1A ON4 K1A ON4

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ISBN 0-315-87849-5

Canada Short title

Integrated pest management approach for the sorghum shoot fly

Joanny O. Zongo i i • ABSTRACT

Ph.D. Joanny O. Zongo Entomology

A four-year (1988 to 1991 inclusive) field and laboratory study was undertaken to determine and select the components that could be integrated to control the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), in 8urkina Faso, West Africa. Nine approaches were investigated: 1) monitoring adult shoot fl ies: 2) sequential sampling based on egg and dead heart counting: 3) cultural practices (sowing dates and plant densities, intercropping sorghum-cowpea): 4) use of resistant cultivars: 5) use of natural insecticide from the neem tree Azadirachta indica A. Juss. (Meliaceae): 6) effects of intercropping sorghum-cowpea on the natural enemi~~ of the shoot fly: • 7) spider fauna in pure sorghum and intercropped sorghum-cowpea: 8) parasitism of the shoot fly by a larval parasitoid, Neotrichoporoides nyemitawus Rohwer; and 9) the biology of an egg parasitoid, Trichogrammatoidea simmondsi Nagaraja. These nine approaches were divided into four main components: 1) monitoring populations, 2) cultural practices, 3) natural and chemical pesticides, and 4) biological control that could be integrated to control the shoot fly. Among these components, monitoring populations (egg sampling), cultural practices, and use of natural pesticides could be util ised at the farmer level • • iii • RËSUMË Doctorat Joanny O. Zongo Entomologie

Approche de Lutte Intégrée Pour la Mouche des Pousses du Sorgho, Atherigona soccata Rondani (Diptère: Muscidae), au Burkina Faso.

Quatre années d'études au champ et au l aboratoi re (1988-1991 inclus) ont été effectuées en vue de déterminer et de sélectionn~r des composantes de lutte intégrée pour la mouche des pousses du sorgho, Atherigona soccata Rondani (Diptère: Muscidae), dans les conditions du Burkina Faso. Neuf approches ont été examinées: 1) dépistage des mouches adultes, 2) échantillonnage séquentiel basé sur le comptage des oeufs et des coeurs morts, 3) les pratiques culturales (dates et densités de semis, culture associée sorgho-niébé), 4) utilisation de • cultivars résistants, 5) utilisation des extraits naturels du neem, Azadirachta indica A. Juss. (Meliaceae), 6) effets de la culture associée sorgho-niébé sur les ennemis naturels de la mouche, 7) la faune aranéologique en culture pure du sorgho et en culture associée sorgho-niébé, 8) parasitisme de la mouche par un endoparasitoïde larvaire, Neotrichoporoides nyemitawus Rohwer, et 9) la biologie d'un parasitoïde des oeufs, Trichogrammatoidea simmondsi Nagaraja. Ces neuf approches ont été divisées en quatre principales composantes: 1) dépistage des populations, 2) pratiques culturales, 3) pesticides naturels et chimiques, et 4) lutte biologique. Parmi ces composantes, le dépistage des populations (échantillonnage des oeufs), les pratiques culturales et l'utilisation des extraits du neem pourraient être .' utilisés en milieu paysan. • ;v

Suggested short t;t le: Integrated pest management approach for the • sorghum shoot fly.

Joanny O. Zongo

• • v

DEDICATIDN

TD My wife Rasmata Minoungou~ my sons, Jean-Eudes Wendintoin, and Héribert Guétawendé, • for their great patience.

• vi • ACKNOWLEDGEMENTS Project Supervision l wish to express my great admiration and gratitude to my two supervisors: 1) Dr. R.K. Stewart, whose help, support, knowledge, and hospitality have been invaluable. His whole being inspires confidence. 2) Dr. C. Vincent, for his creative ideas, active participation in field work and his kind hospitality. l appreciated his attention in the preparation of the project and his dil igence in reviewing the thesis. Staff Members l express my gratitude to Dr. J.E. McFarlane, Chairman of the Department of Entomology, who allowed me to transfer from the M.Sc. to the Ph.D. program; Dr. S.B. Hill, Dr. W.N. Yule, Dr. P.M. Sanborne, Dr . D.J. Lewis and Dr. 6.B. Dunphy for their constructive guidance during • my training. Special thanks to Dr. S.B. Hill who commented on chapter 6. Special thanks to Alan Godfrey for his help in teaching me English and Dr. Shahrokh Khanizadeh for statistical advices. l also thank Pierre Langlois for advice on computer programs and other technical aspects; Monique Verrette, Marie J. Kubecki and Diane King for their excellent guidance en administrative policies. Special thanks to Marie J. Kubecki for her diligence in typing the thesis. External Scientists l am particularly indebted to Mr. J.C. Deeming, National Museum of Wales, Cardiff, U.K., who taught me the art and science of shoot fly identification at Cardiff. He described and named a new species of shoot fly that l identified. l also appreciated his kind hospitality. Dr. B. Pintureau, INRA-INSA, Villeurbanne, Lyon, France, who • taught me how to identify and rear Trichwgrammatidae species and for vii • his great hospitality. l also appreciated the kind hospitality of Dr. B. Delobel at Lyon. In Paris, l had helpful discussions with Dr. A. Delobel, ORSTOM, who gave me reprints of his publ ished papers and his thesis in microfilm format on the sorghum shoot fly. Dr. R.A. Humber, from USDA Plant Protection Research, US Plant, Soil & Nutrition Lab., Ithaca, New York, USA, for fungal identification. Dr. K.F. Nwanze formerly at ICRISAT, Hyderabad, India, furnished t:1e model for the ICRISAT trap. Dr. C. Dondale Biosystematic Research Center, Ottawa, Canada, and Dr. R. Jocqué, Musée Royal de L'Afrique Centrale, Tervuren, Belgium, for their help in spider identification. Dr. L. Pedigo, Dept. Entomology, Iowa State University, USA, • commented on the second chapter. Dr. M.B. Isman, Dept. of Plant Science, University of British Columbia, Vancouver, Canada, for assessing azadirachtin content. Colleagues and Friends 1) Canada Special thanks are expressed to the following (in no particular order): Marie-Claude Larivière for advice on my transfer to the Ph.D. level and teaching me WordPerfect on the IBM microcomputer. Graham Thurston for his help and advice on my Comprehensive Exam, and teaching me SAS, Dr. Gérald Lafleur for general advice before my studies. Mr. François Fournier for commenting on chapter 4. • Ed Zaborski for advice on SAS. viii • Christine Noronha for her advice on my Comprehensive Exam, Dr, Mohammad Javahery and Sue Johnson for advice and assistance on my first English seminar, Georges-Marie Momplaisir, Tarik Kassay, Mrs, Wanga. Jean-Piel're Delond and Maria, François Genier, Alexander Yaku, Getano. Yacine and Andrew Frowd, François Fournier, and Doulaye Traoré for their pleasant company. 2) Burkina Faso Dr. Dona Dakouo, INERA, Farako-Bâ, for suggestions on my first field work, Dr. Da Sansan, INERA, Farako-Bâ, for providi ng l ocal sorghum cultivars, Blaise K. Kaboré for providing local sorghum cultivars and encouragements, • Napon Marcellin, INERA, Farako-Bâ, for allowing trap installation in a sorghum field in 1988, Dr. M. Muleba, IITA/SAFGRAD, Ouagadougou, for his help in assessing yields of intercropped sorghum-cowpea, Mr. Jérémy Ouédroago, IITA/SAFGRAD, Ouagadougou, furnished seeds of cowpea, Dr. Luc Couture and Célestin Kaboré for fungi and bacteria isolation, My technician Tou Fadoua Malick and the field workers Ouattara Salif, Ouédraogo Boukary, Yabré Seydou, Tiemtoré Marcel, longo François, and longo Oumarou for their help in collecting data, Da Angèle and Solange Dabiré for typing my project, My family-in-law, particularly my mother-in-law; Noelie Yerbanga, • Hubert R. longo, Mathieu and Adrienne Ramdé, Seydou loma, Blaise K. ix • Kaboré, Joanny B. Ouattara, Dominique Compaoré, Adama Sanou, Pierre Yaméogo, Aimé Zongo, Pascal Zongo and Apollinaire Zongo for their constant attention to my family, Zongo Tanga, and all my bothers, sisters, parents, and friends in Koudougou, Ouagadougou, and Bobo-Dioulasso, for their attention. Institutions This research is part of a Plant Protection Project funded by the Canadian International Development Agency (CIDA 960325) managed by Agriculture Canada Research Station at Saint-Jean-sur-Richelieu, Québec, Canada. l would like to express my gratitude to the personnel of Saint­ Jean-sur-Richel ieu Research Station and in particular to its former Director, Dr. Claude B. Aubé, the current Director Dr. Denis Demars, Dr. Pierre Martel, formerly Directeur of CIDA Plant Protection Project • in Burkina Faso, G. Benharrosh, senior administrator of the project in Burkina Faso, Dr. Guy Boivin, Jacques Daneau, Ian Wallace, L-G. Simard and Benoit Rancourt for their various assistance. Special thanks to Dr. Pierre Martel who, as interim Director of the project, accepted with sound judgment my transfer to the Ph.D. level. The International Institute of Entomology, London, U.K. identified insect specimens. Biosystematic Research Center, Ottawa, Canada, and Musée Royal de L'Afrique Centrale, Tervuren, Belgium, for accepting vou cher specimens. INRA-INSA, Villeurbanne, Lyon, France, for allowing me to use their laboratory facilities. ' Thanks are also extended to the personnel of the Plant Protection .' Laboratory in Bobo-Dioulasso, Burkina Faso, for the facilities, x • Special thanks to Burkina Faso government through Blaise Kaboré, Amidou Ouédraogo, (Chiefs of Plant Protection Laboratory, Bobo­ Dioulasso), Combari Abdoulaye and Blaise T. Ouédraogo (Directors of Plant Protection and Conditioning, Ouagadougou), for allowing the time to complete this study. Finally, l wish to express my great gratitude and love to my wife, Rasmata Minoungou, my sons, Jean-Eudes Wendintoin, and Héribert Guétawendé, to whom l dedicate this work. Without Rasmata's support, understanding and love, this work could not have been completed .

•

• xi • CLAIH5 TD DRIGINALITY 1. A new species of shoot fly, Atherigona zongoi Deeming, was discovered and described. 2. Thirteen shoot fly species were found new to Burkina Faso. 3. First record of Trichogrammatoidea simmondsi Nagaraja, an egg parasitoid of shoot fly. 4. First record of a new predator of shoot fly eggs, Tapinoma sp. (Hymenoptera: Formicidae). 5. First record of fungus, Fusarium sp., attacking the shoot fly eggs. 6. First record of bacterium, Corynebacterium sp., attacking the shoot fly eggs. 7. First record of Bracon sp. (Hymenoptera: Braconidae) attacking the shoot fly larvae. B. First record of Hockeria sp. (Hymenoptera: Chalcididae) attacking • the shoot fly larvae. 9. A complex of spiders (families, genera and species) associated with shoot flies was found and listed for the first time. 10. This is the first study on the effects of the neem seed extracts, a natural pesticide on shoot fly egg and larval mortality. Il. A sequential sampling based on dead heart and egg counti ng was established. 12. This is the first study on the behavior of Neotrichoporoides nyemitawus Rohwer, a parasitoid of shoot fly larvae. 13. Amethod was developed to rear Neotrichoporoides nyemitawus Rohwer for the first time. 14. First demonstration tiGt Neotrichoporoides nyemitawus Rohwer cannot • prevent dead heart formation. xii • 15. First demonstration that second instar of the shoot fly is more parasitized than first and third instars by Neotrichoporoides nyemitawus Rohwer. 16. First demonstration that shoot fly eggs less than 24 h old are more parasitized than > 24 old eggs by Trichogrammatoidea simmondsi Nagaraja. 17. A simple method was developed to rear Trichogrammatoidea simmondsi Nagaraja for the first time. 18. Thi sis the fi rst study on the biology of Trichogrammatoidea simmondsi Nagaraja, an egg parasitoid of shoot fly. 19. First record of superparasitism on shoot fly eggs by Trichogrammatoidea simmondsi Nagaraja. 20. First demonstration of the beneficial effect of intercropped sorghum-cowpea on Neotrichoporoides nyemitawus. • 21. First demonstration of the" beneficial effect of intercropped sorghum-cowpea on Meioneta prosectes Locket, and Steatoda badia Roewer. 22. A new trap (Multi-Pher) was found to be effective in catching the shoot flies for the first time. 23. Local sorghum cultivars in the Province of Houet (Bobo-Dioulas~o, Burkina Faso) were found to be susceptible to the shoot fly for the first time. 24. Overall, this is the first practical IPM approach for ~ontrol of the shoot fly in Burkina Faso . • xiii • TABLE OF CONTENTS 1 Page Abstract i i Résumé . i i i Suggested Short Title iv Dedication .. • v Acknowledgments vi Claims to Originality xi List of Figures xx List of Tables xxi 1. Introduction 1 2. Literature Review 6 2.1. "Importance of Sorghum in Burkina Faso 7 2.2. Constraints to Sorghum Production 7 • 2.3. Insect Pests of Sorghum 8 2.4. The Sorghum Shoot Fly . 10 2.4.1. Origin and Distribution 10 2.4.2. Taxonomy ..... 10 2.4.2.1. Nomenclature 10 2.4.2.2. Classification 11

2.4.2.3. Identification 11 2.4.3. Biology and Ecology 12 2.4.3.1. Egg. 12 2.4.3.2. Larva 14 2.4.3.3. Pu pa 14 2.4.3.4. Adult 15

• l Papers published or submitted to Journals are indicated. xiv • 2.4.3.5. Life cycle and voltinism .. 16 2.4.3.6. Population growth regulators 17 2.4.3.6.1. Abiotic factors 17 2.4.3.6.2. Biotics factors 17 2.4.4. Host-Plants . 17 2.4.4.1. Food-Plants 17 2.4.4.2. Damage 18 2.4.5. Rearing 19 2.4.6. Control 19 2.4.6.1. Cultural control 19 2.4.6.1.1. Planting time 19 2.4.6.1.2. Sanitation and plant density 20 2.4.6.1.3. Crop diversity 20 2.4.6.1.4. Fertilization 20 • 2.4.6.1.5. Host-plant resistance 21 2.4.6.1.5.1. Mechanisms of resistance 21 2.4.6.1.5.2. Bases of resistance 21 2.4.6.2. Biological control 22 2.4.6.3. Chemical control 23 2.4.6.4. Monitoring and surveying 24 CONNECTING STATEMENT .... 25 3. Monitoring Adult Sorghum Shoot Fly, Atherjgona soccata Rondani (Diptera: Muscidae), and Related Species in Burkina Faso 26 3.1. Abstract .. 27 3.2. Introduction 28 3.3. Materials and Methods 29 3.4. Resul ts . 30 • 3.5. Discussion 32 xv • 3.6. References 35 3.7. Tables .. 38 CONNECTING STATEMENT 44 4. Time-sequential Sampling of Sorghum Shoot Fly, Atherigana saccata Rondani (Diptera: Muscidae), in Burkina Faso 45 4.1. Abstract .. 46 4.2. Introduction 47 4.3. Materials and Methods 48 4.4. Results . 51 4.5. Discussion 52 4.6. References 55 4.7. Tables. . 58 CONNECTING STATEMENT 65 5. Influence of Cultural Practices on Sorghum Yields • and Incidence of Sorghum Shoot Fly, Atherigana saccata Rondani (Diptera: Muscidae), in Burkina Faso 66 5.1. Abstract .. 67 5.2. Introduction 68 5.3. Materials and Methods 69 5.3.1. Experimental Series A 69 5.3.2. Experimental Series B 71 5.4. Results .... 72 5.4.1. Series A 72 5.4.1. Series B 72 5.5. Discussion 73 5.6. References 76 5.7. Tables and Figure 1. 80 • CONNECTING STATEMENT •.... 86 xvi • 6. Screening of Local Cultivars for Resistance to Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae) 87 6.1. Abstract . 88 6.2. Introduction 89 6.3. Materials and Methods 90 6.4. Results 91 6.5. Discussion 92 6.6. References 95 6.7. Tables .. 97 CONNECTING STATEMENT 100 7. Effects of Neem Seed Kernel Extracts on Egg and Larval Survival of the Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae) 101 7.1. Abstract 102 • 7.2. Introduction 103 7.3. Materials and Methods 104 7.3.1. Field experiments 104 7.3.2. Laboratoryexperiments 106 7.4. Results . 108 7.4.1. Field experiments 108 7.4.2. Laboratoryexperiments 108 7.5. Discussion 109 7.6. References 113 7.7. Tables and Figure 2 117 CONNECTING STATEMENT ....• 122 • xvi i • 8. Effects of Intercropping Sorghum-Cowpea on Natural Enemies of the Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae), in Burkina Faso 123 8.1. Abstract .. 124 8.2. Introduction 125 8.3. Materials and Methods 125 8.3.1. Egg parasitoid sampling 126 8.3.2. Larval and pupal parasitoids sampling 127 8.3.3. Fungi and bacteria sampling 127 8.4. Results . 128 8.4.1. Shoot fly complex 128 8.4.2. Egg natural enemies 128 8.4.3. Larval and pupal parasitoids 129 8.5. Discussion 130 • 8.6. References 135 8.7. Tables and Figure 3 139 CONNECTING STATEMENT ..... 144 9. Spider Fauna in Pure Sorghum and Intercropped Sorghum-Cowpea in Burkina Faso 145 9.1. Abstract .. 146 9.2. Introduction 147 9.3. Materials and Methods 148 9.4. Results . 149 9.5. Discussion 151 9.6. References 154 9.7. Tables and Figure 4 158 • CONNECTING STATEMENT ..... 163 xviii • 10. Parasitism of the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), by Neotrichoporoides nyemitawus Rohwer (Hymenoptera: Eulophidae) 164 10.1. Abstract 165 10.2. Introduction 166 10.3. Materials and Methods 167 10.4. Results . 169 10.5. Discussion 170 10.6. References 173 10.7. Tables 176 CONNECTING STATEMENT 179 Il. Biology of Trichogrammatoidea simmondsi Nagaraja (Hymenoptera: Trichogrammatidae) on sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae) eggs 180 • 11.1. Abstract 181 11. 2. Introduction 182 11.3. Materials and Methods 183 11. 4. Results . 184 11. 5. Discussion ~85 11. 6. References 187 11. 7. Tables 188

• xix • 12. General Discussion and Conclusion 191 13. References ...... 198 Appendix 1. Manuscripts and Presentations Based on this Thesis 227 Appendix 2. Atherigona zongoi: trifoliate process and hypopygial prominence; morphological characters used for identification 230 Appendix 3. Sorghum shoot fly, Atherigona soccata: adult, immature stages and damage ...... •.•...... 231 Appendix 4. Copyright waiver of "Monitoring Adult Sorghum Shoot Fly Atherigona soccata Rondani (Diptera: Muscidae) and Related Species in Burkina Faso" by Zongo et a7. (1991) 233 •

• xx LIST OF FIGURES • Page l. Spatial arrangement of sorghum and cowpea rows in five cropping systems ...... · . 85 2. Shoot fly eggs decomposed 24 h after treatment with neem aqueous extracts ...... · . 121 3. Percentages of egg and larval parasitism due to Neotrichoporoides nyemitawus and Trichogrammatoidea simmondsi in two cropping systems in Burkina Faso ..... 143 4. Total spider numbers (spiderlings and adults) per five rows in three cropping systems in Burkina Faso ·... 162 5. Approaches to sorghum shoot fly 1PM investigated • in this thesis ...•.•...... 197

• xxi • LIST OF TABLES Page l. Major insect pests of sorghum of economic importance in the world ...... 9 2. Atherigona spp. catches in four trap models in Burkina Faso 1988 and 1989 ...... 39 3. Sorghum shoot fly Atherigona soccata (male + female) catches in four trap models in Burkina Faso 1988, 1989 .. 40 4. Relative abundance of Atherigona and Acritochaeta males captured in Burkina Faso, 1988, 1989 41 5. Time required to collect and count shoot flies from four trap models in the field, Burkina Faso, 1988 42 6. Adult shoot flies (Atherigona spp.) monthly captures, rainfall and relative humidity in southwestern • Burkina Faso 43 7. Endemie (m,) and (m,) outbreak population configurations of Atherigona spp. eggs. (n= 30) and dead hearts (n= 100), Burkina Faso ... ••...• 59 8. Sorghum shoot fly egg distribution on leavesin three localities, Burkina Faso, (1988 and 1989 data pooled) 60 9. Mean (n= 30), variance, and dispersion characteristics of Atherigona spp. eggs on sorghum in three localities, Burkina Faso .. 61 10. Mean (n= 100), variance, and dispersion characteristics of dead hearts caused on sorghum by Ahterigona spp. in three localities, Burkina Faso ..••.•• 62 Il. Time-sequential sampling plan based on egg counts of •• sorghum shoot fly Atherigona soccata .... 63 xxii • 12. Time-sequential sampling plan based on dead heart counts caused by the sorghum shoot fly, Atherigona soccata . 64 13. Yields and Land Equivalent Ratio (LER) for intercropped sorghum-cowpea, in 1988 at Matourkou, Burkina Faso .... 81 14. Yields and Land Equivalent Ratio (LER) for intercropped sorghum-cowpea, in 1989 at Matourkou, Burkina Faso .. , 82 15. Average number of eggs laid, percentage of plants with eggs and percentage of dead hearts due to A. soccata in four cropping systems in Burkina Faso .... 83 16. Effect of sowing dates on yield and % head hearts caused by the sorghum shoot fly Atherigona soccata at Matourkou, Burkina Faso, in 1988 and 1989 ...... 84 17. Mean number of shoot fly eggs/ 10 plants and me an percentage of dead hearts observed in 54 cultivars • of sorghum at Matourkou, Burkina Faso .... 98 18. Mean number of eggs and me an percentage of dead hearts observed in 9 cultivars of sorghum, Matourkou, 1990, 1991 99 19. Effect of neem se~J kernel extracts on egg survival and dead heart formation due to A. soccata at Matourkou, Burkina Faso ...... •...... , . 118 20. Effect of neem seed kernel extracts on the egg mortality of A. soccata in laboratory conditions, Burkina Faso .•...... 119 21. Effect of aqueous neem seed kernel extracts on larval mortality of A. soccata in 1991, Burkina Faso...... 120 22. Abundance of shoot flies species (male and female) emerging from larvae collected from sorghum shoots • at Matourkou, Burkina Faso ...... 140 xxiii • 23. Average percent parasitism due to Neotrichoporoides nyemitawus and Trichogrammatoidea simmondsi on sorghum shoot fly eggs and larvae in intercropped sorghum-cowpea in Burkina Faso .. . 141 24. Total number of shoot fly parasitoid species collected in Burkina Faso .••. . ..•... 142 ?5. Mean number of spiders (spiderlings and adults, all species confounded) per five rows collected in two cropping systems in Burkina Faso . ... 159 26. Total number of spider species (spiderlings and adults) collected in two cropping systems in Burkina Faso in 1990 and 1991 (n = 156, identified to at least genus) . 160 27. Relative abundance of spider families and species collected in three cropping system in Burkina Faso • in 1990 and 1991 ••..•..... ' .... 161 28. Mean percentage of larval parasitism in relation to period of exposure to Neotrichoporoides nyemitawus 177 29. Ouration of l ife-cycle parameters of Neotrichoporoides

nyemitawus in the laboratory {26 (± 1) 0 C, 75% R.H, (± 2) and 12:12 (LlO) ..•. • 178 30. Percentage of A. soccata eggs parasitized by T. simmondsi and number of exit holes per egg •.•••.. 189 31. Relative size of T. simmondsi immature stages (2~ C, 60-65% R.H.) ••••.•.• 190 • • 1

• 1 INTRODUCTION

• 2 The sorghum shoot fly, Atherigona soeeata Rondani (Diptera: • Muscidae), is a key pest of sorghum, Sorghum bieo7or L. (Moench) in Burkina Faso (Bonzi 19B1, Nwanze 1988). In 1986, the National Sorghum - Millet - Maize Board (SOMIMA) recommended that more studies be undertaken on the shoot fly, particularly in areas where sorghum production is important. The Province of Houet, whose Bobo-Dioulasso is the administrative center, produces over 9% of the national sorghum production (Ministère de l'Agriculture et l'Elevage 1988). It has been well established that a single method approach to control any agricultural insect pest is usually inadequate and leads to fail ures. Integrated Pest Management (IPM), defined in a practical context as "The farmer's best mix of control tactics in comparison with yields, profits and safety of alternatives" (Iles and Sweetmore 1991), is the ideal approach to control the shoot fly (Jotwani 1981). To • apply IPM, various tactics have to be investigated and sel ected according to local conditions. The hypothesis examined here was that it is possible to develop an Integrated Pest Management program for the shoot fly in Burki na Faso. The present work, based on a four-year (1988 to 1991 inclusive) field and laboratory study, was done to determine the components that may be integrated to control the shoot fly in Burkina Faso conditions. Nine chapters presented here, deal with (in order of appearance) monitoring adult shoot flies; time-sequential sampling based on egg and dead heart counting; influence of cultural practices; use of resistant cultivars; use of natural insecticide from the neem tree Azadirachta il'/die~ A. Juss. (Mel iaceae); effccts of intc:-croppin; sorghum-cowpea en the natural enemies of the shoot fly; spider fauna in pure sorghum and • intercropped sorghum-cowpea; parasitism of the shoot fly by 3 • Neotrichoporoides nyemitawus Rohwer; and the biology of Trichogrammatoidea simmondsi Nagaraja. The present thesis format, accepted by the Faculty of Graduate Studies and Research and the Department of Entomology, Macdonald Campus of McGill University, requires a full citation of a section B, 2 (Manuscri pts and Authorshi p), of the Guidel ines Concerni ng Thesi s Preparation of the Faculty of Graduate Studies and Research. "The candidate has the option, subject to the approval of their Department, of including as part of the thesis the text, or duplicated published text, of an original paper or papers. - Manuscript-style theses must still conform to all other requirements explained in the Guidelines Concerning Thesis Preparation. - Additional material (procedural and design data as well as descriptions of equipment) must be provided in sufficient detail (eg. • in appendices) to allow clear and precise judgement to be made of the important and originality of the research report. - The thesis should be more tllan a mere collection of manuscripts published or to be published. It must include a general abstracto a full introduction and literature review and a final overall conclusion. Connecting texts which provide logical bridges between different manuscripts are usually desirable in the interest of cohesion. It is acceptable for theses to include, as chapters, authentic copies of papers already published, provided these are duplicated clearly and bound as an integral part of the thesis. In such instances. connecting texts are mandatory and supplementary explanatory material is al ways necessary. - Photographs or other materials which do not duplicate well must be • included in their original form. 4 • While the inclusion of manuscripts co-authored by the candidate and others is acceptable, the candidate is reguired ta make an explicit statement in the thesis of who contributed ta such work and ta what extent, and supervisors must attest ta the accuracy of the claims at the Ph.D. Oral Defense. Since the task of the Examiners is made more difficult in these cases, it is in the candidate's interest ta make the responsibil ities of authors perfectly clear". l followed the rules of scientific writing given in the CBE Style Manual (1983) and the MLA Handbook for Writers of Research Papers (Gibaldi and Achtert 1988). l wrote each chapter ta be presented ta a specific scientific journal according ta the requirements of that journal. The first chapter (Monitoring Adult Sorghum Shoot Fly Atherigona soccata Rondani (Diptera: Muscidae) and Related Species in Burkina Faso) was published in Tropical Pest Management (Vol. 37: 235­ • 239) whose copyright waiver is enclosed (appendix 4). Chapter 4 (Ti me­ sequential Sampl ing of Sorghum Shoot Fly Atherigona soccata Rondani (Diptera: Muscidae) in Burkina Faso) is In Press in Insect Science and its Application (Kenya), chapter 7 (Effects of Neem Seed Kernel Extracts on Egg and Larval Survival of the Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae)) is In Press in Journal of Applied Entomology (Germany), chapter 8 (Effects of Intercropping Sorghum-Cowpea on Natural Enemies of the Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae) in Burkina Faso) is In Press in Biological Agriculture &Horticulture (U.K.), while chapters ID and Il have already been submitted ta Insect Science and its Application (Kenya), and Entomophaga (France) respectively. All chapters were reviewed by my supervisors, Dr. R.K. Stewart and Dr. C. Vincent, and by .' the editorial committee of Agriculture Canada, Research Station, Saint- 5 • Jean-sur-Richelieu. Sorne chapters were cowmented on by certain scientists wh en available. All papers were coauthored by my supervisors. 1 used SuperANOVA (version 1.1 for the Macintosh Computer) (Abacus Concepts Inc., 1989), and SAS (version 6.03 for IBM PC) (SAS Institute Inc., 1988) for the statistical analysis of the data. The acknowledgement sections were pooled at the beginning of the thesis whereas references were also pooled at the end of the thesis. 1 deposited voucher specimens in the following institutions: point mounted specimens and wet collections in the Lyman Museum, Macdonald Campus of McGill University, Sainte-Anne de Bellevue, Québec, Canada, the Biosystematic Research Center, Ottawa, Canada, Musée Royal de L'Afrique Centrale, Tervuren, Belgium, and in the Plant Protection Laboratory, Bobo-Dioul asso, Burkina Faso. The exi stence of voucher • specimens was mentioned in each chapter whenever appropriate. This study constitutes the first practical investigation on IPM components that could be applied to control the shoot fly in Burkina Faso .

• • 6

• 2 LITERATURE REVIEW

• 7 • 2.1. Importance of 50rghum in Burkina Faso In Burkina Faso, sorghum is the most importance cereal crop. Its production represents 51.31% of total cereal production (FAD, 1991). Sorghum production in Burkina Faso represents 7.17% of the total cereals produced in Africa, putting Burkina Faso as the first producer in the Sahelian regions (FAD, 1991). Sorghum is grown mainly in central and southern regions and has a wide range of uses: human food (the main dish being locally called "To"), beer (locally called "Dolo"), fuel for cooking and, to a lesser extent fences, baskets and livestock feeding. 2.2. Constraints ta 50rghum Production Constraints on sorghum production are numerous in Burkina Faso. They range from cl imatic constraints (poor water resources) ta low soil fertility, poor sail management, lack of infrastructures, diseases and • insect pests which often cause very severe damage. Overall, constraints may be summarized into technical, economic and sociological. Technicàl constraints are insufficiency of research, and low level of education of farmers (illiteracy). Economic constraints range from lack of local organized markets, low income, to lack of a world market. Sociological constraints are that peasant farmers are in general traditional and conservative, sa sorghum production technology shows a low rate of adoption. Other social constraints include the lack of united action from farmers and the insufficiency of cooperation between researchers. • 8 • 2.3. Insect Pests of Sorghum Although over 100 insect species are known to be pests of sorghum, only some of these are presently of economic importance and belong to the Orders Di ptera, Lepidoptera, and Hemi ptera (Nwanze, 1985). In an International Sorghum Entomology workshop, sorghum insect pests from Eastern Africa (Seshu Reddy and Omolo, 1985), West Africa (Nwanze, 1985), India (Srivastava, 1985), South East Asia (Meksongsee and Chawanapong, 1985), Australia (Passlow et al., 1985), U.S.A. (Pitre, 1985), Mexico (Castro, 1985), Central America (Reyes, 1985) and 8razil (Viana, 1985) were reviewed. From these reviews, it appears that shoot flies, grain midges, stored grain weevils, stem borers, head bugs, aphids, mites are the major pests. The economic importance of each key pest varies with the region . Young and Teetes (1977) and Doggett (1988) reviewed sorghum • insects pests while Teetes et al. (1983) furnished practical identification handbook with excellent coloured photographs. Major widespread pests of economic importance are given in Table 1•

• 9 • Table 1. Major insect pests of sorghum of economic importance in the world. Sorghum Latin name part attacked (common name) Damage Lasses (%)

Seedling Atherigona soccata Dead heart 60-90' (Sorghum shoot fly) Stem Busseola fusca Fuller Dead heart, Nil Chi10 spp. perfored stems (Stem borers) 10', 83' Earhead Contarinia sorghicola Tiny 25"45' Coq. shrunken Seeds (Sorghum midge) Grain Sitophilus oryzae L. Seed and 61.3' (Rice weevil) grain destruction Tribolium castaneum NA Herbst (Red flour beetle) Rhyzopertha dominica NA Fab • (Lesser grain borer) Sitotroga cereallela NA Olivier • (Angoumois math) Ephestia cautella NA Wal k. (Almond math)

= Rai et al. (1978); 'a Harris (1985); , a Jotwani et al. (1971); •• Young and Teetes (1977); '. Leuschner and Sharma (1983); '. Venkatarao et al. (1958), NA = Not available.

• 10 • 2.4. The Sorghum Shoot Fly 2.4.1. Origin and Distribution Atherigona soccata Rondani was first reported from Italy and named by Rondani in 1871. About 43 years later, its injury to sorghum seedl i ngs was fi rst reported by Fl etcher (1914) and by Ba11 ard and Ramachandra Rao (1924) in India. The outbreak areas of A. soccata are widespread in Africa, South and South East Asia. However, it may also be found in Mediterranean Europe and in the Middle East. The present regions of shoot fly distribution in Africa and Asia contain three fourth of the sorghum cultivated area and produce only one third of the sorghum grain crop (FAO, 1975). 2.4.2. Taxonomy There are excellent revi ews of the taxonomy of the Afri can • (Deeming 1971, 1972; Dike 1989a, 1989b) and Oriental (Pont 1972) species of Atherigona. The genus Atherigona comprises 168 known species, five subspecies and one variety (Deeming 1971, 1978). 2.4.2.1. Nomenclature The sorghum shoot fly has been described under different names. This is probably due to its wide distribution. The following names have been reported. Atherigona soccata Rondani 1871 A. indica Malloch 1923 A. indica ssp. infuscata Emden 1940 A. varia ssp. soccata Rondani, Hennig 1961 A. excisa Thomson, Avidov 1961 A. varia Meigen, Yathom 1967 • . ' A survey of the literature shows that there still remains some 11 • difference of opinion as to whether soccata is a subspecies of varia, or a distinct species. However, it is quite definite that A. soccata remains the most predominant species attacking the plants of the genus sorghum. 2.4.2.2. Classification The systematic position of the sorghum shootfly A. soccata is as follow: Super order Mecopteroid Order Diptera Suborder______Brachycera Superfamily Muscoidea Family Muscidae Subfamily Atherigoninae Genus Atherigona • Species soccata 2.4.2.3. Identification The female has head and thorax pale grey, abdomen yellowish with paired brown patches. The male is blacker than the female. The main morphological characters used to identify A. soccata may be divided in two groups : those used for the mal e, and those for the fema le. The shape of the trifoliate process and the hypopygial prominence is useful in identifying male species (Deeming 1971, Pont 1972). The characters used to identify females are the terminalia and especially the form of the eighth tergite (Deemimg 1971, Clearwater 1981). To identify both sexes, the relative position of the three sterno-pleural bristles and the position of anterior cross vein on the • discal cell are valuable. Clearwater (1981) found that the sixth and 12 • seventh ovipositon tergites are val uabl e taxonomic characters, and therefore May be added to those descri bed by Deemi ng (1971). The markings on seventh tergite are particularly valuable for identifying female A. soccata (Clearwater 1981). A key for the identification of male species in the Afrotropical Region was first constructed by van Emden (1940). Further keys to the species of this region were constructed by Deeming (1971) and Dike (l989a). Since 1971, several new species of Atherigona have been described by Deeming (1971, 1972, 1975, 1978, 1979, 1981, 1987) and Dike (1989a, 1989b). 2.4.3. Biology and Ecology Ramachandra Rao and Ballard (1924) were the first entomologists to work on the biology of A. soccata. Their research was the first step, and a bench mark in a long series of investigations • that have continued until the present time on the biology and control of this important pest (Young 1981). 2.4.3.1. f9.9i The eggs are usually laid singly on the underside of the leaves of sorghum seedling, or on young tillers (Kundu and Kishore 1970, Barry 1972). The eggs are white, elongate with a raised flattened, longitudinal ridge (Barry 1972). The following sizes have been recorded. 1.3 mm long and 0.33 mm wide (Kundu and Kishore 1970)

1.3 mm n n 0.6 mm n (Barry 1972)

1.5 mm " "0.30 mm n (Rao and Rao 1956) Ogwaro and Kokwaro (1981) using l ight and scanning el ectron microscopy found that the egg measured 1.3 mm and its ventral surface • had longitudinal ridges allowing the eggs to be attached to its 13 • substrate. Incubation periods vary from 2-3 days (Raina, 1981a) to 2-5 days (Barry 1972). Before hatching, the anterior end of the egg becomes yellowish. Eclosion takes place by a rupturing of the dorsal side first below the tip of the egg shell and its duration is 2-3 minutes (Kundu and Kishore 1970). The number of eggs laid per female depends on the diet used to feed females (Meksongsee et al., 1978, Unnithan and Mathenge, 1983). Meksongsee et al., (1978) reported 440 eggs using dry yeast, sugar, and water to feed females. A maximum of 715 eggs were laid by a female shootfly when fed on Baker's yeast, sugar and water and kept at 3~ C (Unnithan and Delobel, unpubl. cited in Unnithan and Mathenge 1983). Temperature and humidity influence the development of the eggs (Swaine and Wyatt 1954, Nye 1960, Barry 1972, Delobel 1983a, 1983b, Doharey et al. 1977). The optimal temperature for the egg lies between • 20 and 3~C (Del obel 1983a, Doharey et al. 1977). Del obel (l983a) pointed out that the mortality of eggs is high at 1~ C and 3~ C, and no hatching occurs at 1~ C, while embryomic development is inhibited at 37.5" C. Low humidity (30%) increases the duration of egg development (Del obel , 1983b) and decreases egg survival (Doharey et al., 1977, Delobel, 1983b). The distribution of the eggs in field is random (Del obel 1981, Zongo et al. 1991). In field and laboratory, Delobel (1981) found that eggs among sorghum stems were randomly distributed or slightly aggregated. Raina (1981b) found that the female shoot fly uses a marker pheromone to deter repeated oviposition on one sorghum plant. • 14 • 2.4.3.2. Larva The larva represents the hazardous stage for sorghum plants. It measures about 10 mm long and 1.3 mm wide. At hatching, it is white and then becomes light yellow and gradually turns yellowish-brown (Barry 1972). Swaine and Wyatt (1954), Nye (1960) and Rao and Rao (1956) recorded three larval instars, whereas Kundu and Kishore (1970) reported 4 larval instars. Ogwaro and Kokwaro (1980) using a scanning electron microscope described three instars. The three larval instars are similar in general appearance but can be distinguished by the size and shape of the cephalopharyngeal skeleton, spiracular process and general coloration (Ogwaro and Kokwaro 1980). Total' larval period ranges between 8-10 days and there is generally one larva per stem (Swaine and Wyatt, 1954, Nye, 1960, Kundu • and Kishore, 1970, 8arry, 1972, Raina, 1981a). Temperature and relative humidity affect the duration of larval development (Del obel 1983a, Delobel and Unnithan 1983, Doharey et al. 1977). The optimal temperature for a rapid development of the shoot fly preimaginal stages (egg, larval and pupal) is 30 0 C (Del obel 1983, Doharey et al. 1977). 2.4.3.3. Pupa The shoot fly pupa is initially light brown, but it becomes dark with age (Barry, 1972). It measures 3.38 to 4.03 mm in length and 1.17 to 1.3 mm in width (Kundu and Kishore, 1970); 3.6 mm long and 1.2 mm diameter (Barry, 1972); 4.8 mm x 1.53 mm (Ogwaro and Kokwaro, 1980). The puparium is barrel shaped. Its posterior end is tapered while the anterior is concave bearing two anterior spiracles (Kundu and • Kishore, 1970). Ten segments (Kundu and Kishore, 1970) or nine (Ogwaro 15 • and Kokwaro, 1981) remain visible. Pupation takes place inside the stem or rarely in the soil. The pupal period takes an average of 10.4 days (Barry, 1972), eight to ten days (Kundu and Kishore, 1970). Temperature influences pupal development (Kundu and Kishore 1970, Delobel 1983a) whereas the R.H. has little effect (Kundy and Kishore 1970). Pupal weight decreases with increasing temperature (Del obel 1983a). The optimal temperature is 30 •C (Kundu and Kishore 1970, Del obe1 1983a). 2.4.3.4. Adult The adult shoot fly appears simil ar to the hou se fly Musca domestica Linné, but it is smaller (Barry 1972). The shoot fly measures 4.42 mm to 5.2 mm in length. It is generally diurnal (Raina (1982). Studying the daily rhythms of oviposition, egg hatching and adult eclosion, Raina (1982) found no eggs laid during the scotophase. • However, Swaine and Wyatt (1954) and Barry (1972) found that eggs were laid at night as well as during the day. In Burkina Faso, the sex ratio male:female was 1:2.84-1:4 (Bonzi, 1981), 1:2.66; 1:4.45 (Zongo et a7., 1991). In Sénégal, Gahukar (1987) collected 80-97% of females using fish meal traps. However, when shoot flies were reared from sorghum plants with dead hearts, the sex ratio was one male for three females (Gahukar, 1985). Clearwater (1981) collected 90% females in Kenya whereas Seshu Reddy and Davies (1978) collected 90-99% females in India. The longevity of both male and female depends on environmental conditions (Barry 1972, Kundu and Kishore 1970) and particularly the diet (Meksongsee et a7.1978, Ogwaro 1978a, Unnithan and Mathenge 1983). Adult flies survived for 32.6 days on brewer's yeast, glucose and water • (Ogwaro 1978a), 33.0 days on sorghum aphid honeydew (Unnithan and 16 • Mathenge 1983). Male and female survived 39 and 26 days respectively on ordinary sugar and water (Meksongsee et al. 1978). The flies are attracted by fish meal (Starks 1970). As already mentioned, the temperature and humidity have an effect on the development of A. soccata. At 15·C there is no mating or ovipositon (Del obel 1983a). The combination of 30·C and 90% R.H. is the most favourable condition for the rapid development and multipl ication of the sorghum shoot fly (Doharey et al. 1977). Shoot fly adult females usually do not mate more than once, but males mate several times with virgin females (Unnithan 1981). Unnithan (1981) also found that enough sperm is transferred and stored by the female at the first mating and thus multiple mating is not required for egg fertilization. • 2.4.3.5. Life-cycle and voltinism The literature shows little variation on the biological cycle of A. soccata. The life-cycle ranges between three and four weeks. The foll owing development times from egg to adult have been reported : 16.8 days at 27.22 Oc and unknown relative humidity (Swaine and Wyatt 1954), 17 to 21 days at 32.6 Oc and 50% relative humidity (Kundu and Kishore 1970), 26.7 days at 28.1 Oc and unknown relative humidity (Barry 1972), 21 to 34 days at unknown temperature and relati~"'~iiÛmidity (Ogwaro and Kogwaro 1981). A. soccata is multivoltine. Three generations have been recorded in a three month period by Soto and Laximarayan (1971). Gahukar (1987) found that a l ife-cycle of 3 - 4 weeks allowed A. soccata to produce up to ten generations per year. In China, seven (Shiang-Lin 1977) and ten .' to Il (SHiand-Lin et al. 1981) generations per year have been recorded. 17 • 2.4.3.6. Population growth regulators 2.4.6.1. Abiotic factors Density independent factors influencing the mortality, longevity, fertility of A. soccata are temperature, R.H., and rainfall patterns (Doharey et a7. 1977, Dubey and Yadad 1980, Jotwani et a7. 1970, Delobel 1983a). Jotwani et a7. 1970, pointed out that temperatures > 3~ C and < 1& C, and continuous rainfall are fatal to the shoot fly. 2.4.6.2. Biotic factors Little is known about exact effects of biotic factors on A. soccata. Several natural enemies of eggs (Deeming 1971, Pont 1972, Taley and Takhare 1979, Jotwani 1978, Reddy and Davies 1978) have been reported. Other natural enemies such as birds and spiders (Del obel and Lubega 1983) playon important part in the reduction of adult flies. 2.4.4. Host-Plants • 2.4.4.1. Food - Plants The shoot fly has many food-plants. In addition to sorghum, it also attacks other crop plants such as maize and millet (Nye, 1960) and several wild graminaceaous plants in various parts of Africa (Deeming, 1971), India (Davies and Seshu Reddy, 1980 a) and China (Shiamp-Lin et a7. 1981). For instance in India, Davies and Seshu Reddy (1980a) reared the shoot fly from 21 species of Gramineae. Delobel and Unnithan (1981) and Singh and Raina (1986) found that the wild sorghum and grasses act as reservoir particularly during the dry season . • 18 • 2.4.4.2. Damage Damage done by the shoot fly is very apparent on sorghum seedlings. After hatching, the maggot slowly moves downwards, enters the central shoot and feeds on the growing point causing a typical damage named 'dead heart' (Barry, 1972, Kundu and Prem Kishore, 1970). Raina (1981a) found that the 'dead heart' is caused by cutting the base of the central shoot and that very little damage is done to the growing point by the first instar. The first and the second instars are mainly involved in cutting leaf tissues, whereas the third instar feeds on dead and decaying tissues (Raina 1981a). Dead heart formation is evident within two to three days of pest attack (Barry 1972, Gahukar 1987). The most suceptible stage of the sorghum for infestation was found to be within 21 days after germination (Kundu et al. 1971 and Jotwani et al. 1970). After shoot • fly attack, small seedlings may be killed outright whereas larger seedlings may continue to produce tillers that in turn are attacked (Young 1981). Sometimes plants tiller excessively and produce less grain. Losses in yield result from a reduced stand and a reduction in tiller size (Jotwani et al. 1970). Little is known about economic thresholds (E.T.) or economic injury levels (E.I.L.). Rai et al. (1978a, 1978b) estimated the EIL of shoot fly infestation on the basis of the cost of protection with carbofuran seed treatment and disulfoton granules as soil application. These two insecticides implied economic grain threshold values of 133 Kg and 337 Kg respectively. The EIL ranged from 3.8 to 15 dead hearts on three sorghum cultivars (CSHl, CSH5 and Swarma). • 19 • 2.4.5. Rearing A. soccata may be reared using sorghum seedl ings as wel1 as artificial diet, the main food requirements being protein and carbohydrate. Unnithan (1981) found that free amino acids were more important than proteins in stimulating vitellogenesis in the shoot fly. Seedlings of a susceptible cultivar have been used to rear A. soccata (Soto 1972, Soto and Laxminarayana 1971, Gahukar 1985). Several artificial diets have been developed to rear the shoot fly (Dang et al. 1971, Soto and Laxminarayana 1971, Soto 1972, Moorty and Soto 1978, Meksongsee et al. 1978, Unnithan 1981, Unnithan and Mathenge 1983, Singh et al. 1983). From these diets it has been revealed that sugar is indispensable for female survival and also for the maturation of the eggs • 2.4.6. Control • A survey of l iterature shows that the more promising control measures that received the greatest research emphasis include cultural control, chemical control (use of systemic insecticides) and the development of high yielding resistant cultivars. 2.4.6.1. Cultural control 2.4.6.1.1. Planting time Many workers (i.e. Brenière 1972, Shri Ram et al. 1976, Gandhale et al. 1983, Gahukar 1987) found that shoot fly damage was lower with early planting times than later ones. However, in China, damage caused by the first generation of the shoot fly was the heaviest and early sown sorghum suffered from serious damage (Shiang-Lin et al. 1981). Synchronous planting times are recommended to avoid or to reduce A. soccata damage. Young (1981) pointed out that continuous cropping • over several months favors population build-up and fly injury. 20 • 2.4.6.1.2. Sanitation and plant density In Kenya, A. soccata survives the off season by living in sorghum stubble and wild sorghum. Removal and destruction of these plants after harvest would disrupt the carry-over of the pest (Unnithan et al. 1985). Removal and destruction of dead heart injured plants from infested fields are effective practices to reduce the population of the sorghum shoot fly (Ponnaiya 1951, Delobel 1982). The use of high seedling rates (40 Kg/ha) and thinning of infested plants is also an effective control practice (Ponnaiya 1951, Young 1981). This method is based on the fact that A. soccata laids its eggs randomly (Delobel, 1981, Zongo et al., 1992) and that a sorghum shoot can sustain only a single instar larva (Meksongsee et al., 1981). Delobel (1982) found 2 that in low density plots (22 plants/m ), plants received 3.35 times 2 more eggs than plants in higher density plots (704 plants/m ). • 2.6.6.1.3. Crop diversity Little work has been done on crop diversity and reseach results seem to be not useful in field conditions. Raina and Kibuka (1983) studied the effect of intercropped maize and sorghum on the oviposition and survival of the sorghum shoot fly and found that no more than 6% of the maize plants received eggs compared with 61% of the sorghum plants. Venugopal and Palanippan (1976) reported that A. soccata damage was more severe wh en sorghum was intercropped with groundnut. 2.4.6.1.4. Fertilization Phosphorus fertilization reduced shootfly incidence in rainfed sorghum (Bangar 1985). He also found that the incidence of dead hearts was inversely proportional to the application of graded levels of Phosphorus. The lowest incidence of dead hearts was observed where • Phosphorus was placed 50 Kg P20s/ha in the vicinity of available soil 21 • moisture. Appl ication of nitrogenous fertil izers at 50 kg No/ha, reduced the incidence of the shoot fly (Reddy and Rao 1975, Mote and Kadam 1983). 2.4.6.1.5. Host-plant resistance 2.4.6.1.5.1. Mechanisms of resistance First screening of a sizable world sorghum collection for A. soccata resistance was made by Ponnaiya in October 1944 (Young 1981). In South India, Ponnaiya (1951) screened 214 sorghum cultivars and found that only 15 cultivars were tolerant to the shoot fly attack and that the percentage of healthy seedlings ranged from la to 84. In 1951, he noted the presence of silica bodies in the third and fourth leaf sheaths of tolerant cultivars and concluded that these silica bodies were the mechanism of resistance. After this work, a long series of research has been undertaken. Today, it is we11 known that the main • mechanisms of resistance are non-preference for oviposition (Jain and Bhatnagar, 1962, Blum, 1967, Jotwani et al. 1971, Singh and Jotwani 1980a), antibiosis (Soto, 1972, 1974, Singh and Jotwani 1980b, Raina et al., 1981), and tolerance or recovery resistance (Doggett and Majisu, 1965, 1966 , Doggett et al., 1970, Singh and Jotwani 1980c, Doggett 1988). 2.4.6.1.5.2. Bases of resistance The main bases of resistance are physico-morphological, and biochemical factors. - Physico-morphological factors These factors deter penetration of the young l arvae or egg laying. The main physico-morphological factors are silica bodies (Ponnaiya 1951), small prickly hairs on the abaxial epidermis (Blum • 1967, 1968), glossy appearance (shining leaves) in the seedling stage 22 • (Jotwani et al. 1971, Maiti et al. 1980, Singh and Jotwani 1980d), long and narrow leaves and fast seedling growth, seedling weight and toughness of leaf sheaths (Singh and Jotwani 1980c, 1980d), col our, texture and shape of leaves (Raina 1982), and presence of trichomes on the abaxial surface of leaves (Maiti and Bidinger 1979). - Biochemical factors Very little is known about the biochemical basis of resistance. Singh and Rana (1986) found that the presence of certain compounds such as hordenine, an alkaloid, and dhurrin, a cyanogenic glucoside in the sorghum plants may act as toxins, feeding stimulants or deterrents in the recognition of the host by the female shoot fly. High nitrogen content (Singh and Narayana 1978) phosphorus (Khurana and Verma 1983) in sorghum plants, and lysine content in leaf sheath (Singh and Jotwani 1980c) is correlated with shoot fly susceptibility. • 2.4.6.2. Biological control Biological control of A. soccata remains the most unexplored control strategy. However, the shoot fly has,a wide range of natural enemi es incl udi ng egg parasitoids [Trichogramma evanescens Westwood (Trichogrammatidae), Trichogramma spp.] (Pont 1972, Taley and Thakare 1979, Deeming 1971, Delobel 1983c), larval parasitoids [Tetrastichus nyemitawus Rohwer (Eulophidae), Aprostocetus sp. (Eulophidae), Cal1itula sp. (Chalcididae), Trichosteresis sp., (Ceraphrontidae)] (Kundu and Kishore 1972, Pont 1972, Taley and Thakare 1979, Del obel 1983c), pupal parasitoids, [Alysia sp. (Braconidae), Pachyneuron sp. (Pteromalidae) Exoristobia deemingi Subba Rao (Encyrtidae) and Syrphophilus bizonarius Gravenhorst (Ichneumonidae)] (Deeming 1971, Taley and Thakare 1979), and unidentifiedbirds and spiders species .' (Del obel and Lubega 1984). Deeming (1983) found that the most common 23 • prey of the wasp Dasyproctus bipunctatus Lepeletier and Brullé (Sphecidae), are Atherigona spp. adults. Delobel and Lubega (1984) mentioned that unidentified birds and spiders are an important group of natural enemies of the sorghum shoot fly. Reddy and Davies (1978) found a predacious mite, Abro7ophus sp. feeding on A. soccata eggs in 1ndia. ln India, parasitism due to Aprostocetus sp. reached 15% in September 1975 and 35% in August 1977 (Jotwani 1978). 2.4.6.3. - Chemical control Earlier workers (Swaine and Wyatt 1954, Rao and Rao 1956, Davies and Jowett 1966, Vedamoorthy et a7. 1965) obtained unsatisfactory results using D.D.T. and BHC sprayed on the foliage of seedlings at weekly intervals. Application of systemic insecticides such as phorate, disyston and carbofuran granules in the furrow of seed at planting time gave effective effects in reducing dead-hearts (Young 1981). • Many others insecticides such as chlorfenvinphos, oncol, dicrotophos, dimethoate, isofenphos, phosalone also gave a positive effect for the control of the sorghum shoot fly (Jadhaw and Jotwani 1982, Shivpuje and Thombare 1983, Mote an Kadam 1984). Carbofuran seed treatment proved to be the most practical effective and economic chemical method to control A. soccata compared to any other insecticides and insecticidal applications (Jotwani et a7. 1972, Shivpuje and Thombare 1983, Mote and Kadam 1984). However this insecticide is more hazardous to handle and the treatment has to be done under strict technical supervision, which limits its use on large scale (Mote and Kadam 1984). The literature reveals no report of A. soccata resistance to any of the insecticides evaluated and recommended for the control of this • pest. 24 • 2.4.6.4. - Monitoring and surveying Fish meal attracted shoot flies (Starks 1970) and was first used in traps to monitor A. soccata (Seshu Reddy and Davies 1978). The trap consisted of a square pan galvanized metal ( 60 x 60 x 7,5 cm) with a lid; fishmeal was placed in a dispenser kept at the center of the trap. The trap was then filled with water (201) to which a small quantity of detergent (100 g) is added. Fishmeal and water are periodically replaced. The square pan metal trap has been replaced by a plastic traps which is simple and easy to handle (Taneja and Leuschner 1986). It consisted of one liter plastic jar with fly entry holes on the sides. The top of the jar contained a fish meal dispenser and a vial containing a volatile insecticide. The bottom was filled with a plastic funnel whose outlet is attached to a collecting jar. The fermented fish • meal may remain attractive for a week . Zongo et a7. (1991) compared the previous traps with two others (Multi-Pher and Conical) and concluded that the ICRISAT (Taneja and Leuschner 1986) and Multi-Pher are more appropriate. Mohan and Pras ad (1991) developed a fish meal powder formulated with three insecticides (fenthion 80 EC, quinalphos 40 EC and propoxur 1%) and found that propoxur formulation reduced si9nificantly shoot fly damage.

• • 25

CONNECTING STATEMENT

Modern pest management cannot operate without estimates of pest population densities (Ruesink and Kogan 1982). To estimate pest population densities, three main methods are used, namely absolute methods, relative methods and population indices (Ruesink and Kogan 1982). Shoot fly population densities are usually estimated using relative methods (Bonzi 1981, Bonzi and Gahukar 1983, Gahukar 1987) as these techniques are easier than absolute on es (Ruesink and Kogan • 1982). Monitoring shoot fly adults may generate useful information for improving control strategies. For example, knowing the outbreak periods during a cropping season may help to schedule planting times and screening programs. Chapter 3 deals with how to monitor shoot fly populations using different traps. The main goal of this chapter iS,to determine the shoot fly species array and to investigate the possibility of using more efficient traps than those previously recommended to monitor shoot flies .

• .. 26

3 Monitoring Adult Sorghum Shoot Fly, Atherigona soccata Rondani • (Diptera: Muscidae), and Related Speices in Burkina Faso •

Published in Tropical Pest Management, 37: 321-235 [1991] • Authors: J.O. ZONGO, C. VINCENT, and R.K. STEWART . 27 • 3.1. AB5TRACT Fish meal was used as attractant in four trap types for assessing the rel ati ve abundance and speci es composi ti on of sorghum shoot fl ies. which are major pests in the wetter southern zones of Burkina Faso. Trapping was carried out in 1988 and 1989 during the rainy season in Bobo-Dioulasso. Three trap models were effective in catching Atherigona soccata: 1) water trap, 2) Multi-Pher and 3) ICRISAT (International Crops Research Institute for 5emi-Arid Tropics) traps. Multi-Pher and water traps were the most efficient. The advantages and disadvantages of each trap model are discussed. Identification of male shoot flies demonstrated the presence of 34 species of the subgenus Atherigona and two species of the subgenus Acritochaeta, with Atherigona soccata, A. occidenta7is Deeming and A. tomentigera van Emden being predominant . Thirteen species were new records to Burkina Faso: A. aberrans Malloch, • A. africana Deeming, A. fi7i7oba Deeming, A. gabonensis Deeming, A. gi7vifo7ia van Emden, A. griseiventris van Emden, A. hya7inipennis van Emden, A. med7eri Deeming, A. nigrapica7is Deeming, A. pu77a Wiedemann, A. ruficornis Stein, Acritochaeta yorki Deeming. A new species Atherigona (s.s.) sp. n. will be described elsewere' .

• 1 The species was described and named as Atherigona zongoi, see appendix 2. 28 • 3.2. INTRODUCTION The sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), is one of the most destructive and widely distributed pest of sorghum in Africa and Asia (Young, 1981). In Burkina Faso it is a key limiting factor of Sorghum bicolor (Linné, Moench) production in the wetter southern zones, particularly when rainfall dictates delayed planting (Brenière, 1972; Bonzi, 1981; Nwanze, 1988). Several shoot fly species are injurious to sorghum seedlings the most destructive being A. soccata (Deeming, 1971; Baliddawa and Lyon, 1974; Davies et al., 1980; Gahukar, 1985). In Burkina Faso, high shoot fly damage (15-46% of head hearts) has been recorded in farmers' fields (Nwanze, 1988). Bonzi (1981) Bonzi and Gahukar (1983), respectively, found 22 and 24 species of Atherigona, including the subgenus Acritochaeta. Among the species so far collected in Burkina Faso, A. • soccata accounted for 14% of the seasonal captures and A. marginifolia, 36% (Bonzi and Gahukar, 1983). To monitor shoot fly adults, two types of trap have been recommended: the water trap (Seshu Reddy and Davies, 1978) and the ICRIS~~~(lnternatinal Crops Research Institute for Semi-Arid Tropics) trap (Taneja a:'d Leuschner, 1986). Both traps use fi sh meal as an attractant (Starks, 1970). _ The present investigations were undertaken to study the relative proportion of sorghum shoot fly species in Burkina Faso and ta test whether another effective trap could be used to monitor adult sorghum shoot fly.

• ' 29 • 3.3. MATERJALS AND HETHODS The experiments were conducted in 1988 at Farako-Bâ and in 1989 at Matourkou, both located ca. la km south of Bobo-Dioulasso (11· ll'N, 4· lS'W). Four types of traps were used during the rainy season: (l) Multi-Pher (Jobin, 1985); (2) ICRISAT insecticide trap (Taneja and Leuschner, 1986); (3) conical (Eckenrode and Arn, 1972): and (4) water trap . The traps were placed 20 m apart in a sorghum fields (3 ha in 1988, 0.5 ha in 1989) in a Latin-square design at 50 cm above ground level. The local cultivar 'Gnofing', known to be susceptible to sorghum shoot fly (Brenière, 1972; Zongo, 1987), was used in both fields. The Multi-Pher ICRISAT and conical traps were held with an iron stake. The water trap consisted of a plate (26 cm diameter) containing 500 ml water and detergent and placed in a circular hole in a 50 cm high table. The ICRISAT trap was made with rubber tubing and a plastic • funnel. Apl astic bag was fill ed wi th 25 9 fi sh me..1 saturated wi·th water. The bait was placed in the traps 24 h later. The plastic bag was perforated around the upper part so that the fish meal odour could escape. A rubber band was used to hold the fish meal in the Multi-Pher trap whereas paper clips were used in the ICRISAT and conical· traps. One gram of a (18,6% Vapona'") dichlorvos strip was placed in the Multi-Pher, ICRISAT and conical traps to kill trapped insects. The dichlorvos strip was taped to the Hulti-Pher and conical traps, and was held in a plastic capsule in the ICRISAT trap. Water and fish meal were replaced in the water trap twice a week, whereas in the Multi~ Pher, ICRISAT and conical traps, fish me al was changed weekly and the insecticide fortnightly• • The traps were placed la days after sowing. The trapping 30 • experiment lasted from 21 July to 17 November 1988 at Farako-Bâ and from 1 August to 17 November 1989 at Matourkou. Flies were collected every 3-4 days for each trap model. Flies were then placed in vials containing 70% alcohol until identification in the laboratory. In 1988 we calculated the time required to empty the traps on two occasions. On the first occasion the time (in minutes) required to collect all insects captured, including Atherigona spp. was recorded twice for each trap model. On the second occasion the time required for collecting only Atherigona spp. from each trap model was recorded four times. These data also allowed estimation of the selectivity of each trap model. At each date of trapping, and for each trap model, a maximum of 100 flies (males and females) were randomly retained for identification. The specimens were kept in 3% potassium hydroxide • overnight before idenfication with Deeming's (1971, 1972, 1978, 1981) and Clearwater's (1981) keys. Data were analysed using LSD test (Steel and Torrie, 1980). Voucher specimens of most species were deposited at the Biosystematics Reseal'ch Center (Agriculture Canada), Ottawa. 3.4. RESULTS In 1988 the number of Atherigona spp. caught in the water, Multi­ Pher, ICRISAT and conical traps was 32 161, 25 336, 14 978, and 4459 respectively (Table 2). The number of A. soccata (males + females) was 1214, 891, 740, and 386 in Multi-Pher trap, water trap, ICRISAT trap. and conical trap respectively (Table 3). In 1989, similar results were

= found but captures of both Atherigona spp. and A. soccata were fewer. Of the total number of Atherigona spp. (76 934, all trap models pooled) captured in 1988, 17 190 specimens were identified representing 22.34% • of the total specimens captured. The sex ratio was one male for five 31 • females. In 1989 the number of keyed specimens was 6139, representin9 49.76% of the total number 12 337. The sex ratio (male:female) was 1:4. In 1988, A. soccata was the predominant species, representin9 32% of males captured followed by A. occidenta7is (14.85%), A. budongoana (7.51%), A. tomentigera (5.63%), A. 7ineata (4.75%), A. truncata (4.03%), A. marginifo7ia (3.59%), A. secrecauda (3.23%), A. peduncu7ata (3.16%), A. mirabi7is (2.65%) and other species. In 1989, A. occidenta7is was the most numerous species (29.97%), followed by A. soccata (19.63%), A. tomentigera (18.22%) and A. 7ineata (4.74%) (Table 4). Thirteen species are new records to Burkina Faso. Anew species, Atherigona (s.s) sp. n., has been found and will be described elsewhere by J.C. Deeming (National Museum of Wales, Cardiff U.K.) from material in our collection and that of R.J. Gahukar (J.C. Deeming, personal • communication). In 1988 and 1989 the sex ratio (male:female) of A. soccata were 1:2.66 and 1:4.45, respectively. Of the total number of species examined in 1988 and 1989 for all trap models pooled, A. soccata (males and females) represented 18.79% and 19.90% respectively. The time required for collecting only Atherigona spp. in conical, ICRISAT, Multi-Pher and water traps was respectively 4, 9, 28 and 32 min (Table 5). The time required to count both Atherigona spp. and other insects caught was 5, 13, 43 and 80 min for conical, ICRISAT, Multi-Pher and water traps respectively (Table 5) . • 32 • 3.5. DISCUSSION The fish meal proved to be an effective bait for monitoring shoot fl ies. Simil ar resul ts have been found by Bonzi (1981), Bonzi and Gahukar (1983), Taneja and Leuschner (1986), Doumbia and Gahukar (1986), Gahukar (1987). However, fish meal was not a specific attractant, hence increasing the time of collection. The four trap models captured six times more shoot flies in 1988 than in 1989. This might be due to factors such as climatic conditions, as Doharey et a7. (1977) observed that high relative humidity is an important factor for sorghum shoot fly development. Rainfall and relative humidity were higher in 1988 than in 1989 (Table 6). Heavy rainfall at the onset and during the cropping period may enhance the growth of grasses and wild sorghum, which are known to be important hosts of shoot flies (Deeming, 1971; Bonzi and Gahukar, 1983; Gahukar, 1985, 1987). • The advantages of the ICRISAT trap have been listed by Taneja and Leuschner (1986) as simplicity, handiness, light weight, low operational costs, and the ability to capture live flies for various purposes. High selectivity by calibration of holes may also be added (Table 5). In the course of our experiment, ants climbed up the iron stake, ate the fish meal or damaged the flies caught. In both Multi­ Pher, ICRISAT and conical traps, a ring of insect adhesive (Tangletrap~) applied to the iron stake solved the problem. The Multi-Pher trap showed similar advantages to those of the ICRISAT. However, its efficacy in catching live flies is reduced bec au se its openings are large and may let the flies e~cape. Although Multi-Pher trap showed the highest selectivity (82.04%), it also captured many other fl ies such as Ca77iphoridae, Sarcophagidae and • Ch7oropidae. Unlike the ICRISAT trap it cannot be made of local 33 • material. The water trap was the most efficient model for capturing Atherigona spp., but it required more time to empty the trap, largely due to wet conditions in which the flies are collected. Water traps also captured many other insects including Ca77iphoridae, Sarcophagidae, Ch7oropidae, and Scarabaeidae. As Taneja and Leuschner (1986) pointed out, the fish meal and water must be replaced frequently in water traps. During collection, more precautions were required to keep the specimens intact. Furthermore, the specimens started to rot after a few days. The conical trap was the least efficient model. Destruction of fish meal by rodents and ants occurred frequently. The trap needs to be refined concerning the location of fish meal. However, it allowed the collector to work in dry conditions and to obtain good material for • identification. Atherigona is a large genus: 168 known species, five subgenera and one variety have been described (Deeming 1971, 1978). The subgenus Atherigona is the largest and contains all the species destructive to graminaceous crops (Deeming, 1978). In Burkina Faso 41 species (39 species of the subgenus Atherigona, two species of the subgenus Acritochaeta) including the species here reported have been collected so far from sorghum and millet fields. The present study revealed 13 species new to Burkina Faso (Table 4). Among the most predominant species captured both in 1988 and 1989, A. soccata, A. tomentigera and A. 7ineata are known to be found in sorghum seedlings (Deeming, 1971). Other species have also bee~found in sorghum shoots. Seshu Reddy and Davies (1978) listed 13 species in India, while Deeming (1971) and • Gahukar (1985) listed nine and seven in Nigeria and Sénégal, 34 • respectively. A. occidenta7is was predominantly captured in 1989 and second in importance in 1988, but larvae have not bean found in sorghum shoots. Females, that were more attracted than males to fish meal bait, represented 73% and 82% of A. soccata captured respectively in 1988 and 1989. Similar results have been found by Bonzi (1981) in Burkina Faso, Clearwater (1981) in Kenya, Gahukar (1987) in Sénégal. The greatest (90-99%) proportion of females has been recorded in India by Seshu Reddy and Davies (1978) using fish meal-baited water traps. Peak captures of both Atherigona spp. and A. soccata were recorded in August and September, confirming the results of Bonzi and Gahukar (1983). In general, these months coincide with heavy rainfall in Burkina Faso. Gahukar (1987) pointed out that the shoot flies abound wh en rainfall is abundant, while Delobel and Unnithan (1983) stressed • the negative effect of heavy rainfall. In conclusion the water trap, Multi-Pher and ICRISAT types might be useful in monitoring and assessing sorghum shoot fly populations. However, for systematic and hi stological studies that require high quality of specimens, ICRISAT and Multi-Pher traps are more appropriate. Although Natarajan and Chelliah (1983) recommended the ICRISAT type at a rate of 12-15 traps per ha, Gahukar (1987) found that the efficiency of fish meal traps in timing control methods for sorghum shoot fly is questionable. Further work is needed to clarify these conflicting statements. • 35 • 3.6. REFERENCES BALI DDAWA , C.W. and LYON, W.F., 1974. Sorghum shoot fly species and their control in Uganda. Proceedings of the Academy of Natural Sciences, 20, 20-22. BONZI, S.M., 1981. Fl uctuati ons sai sonnières des popul ations de la mouche des pousses de sorgho en Haute-Volta. Insect Science and its Application, 2, 59-62. BONZI, S.M. and GAHUKAR, R.T., 1983. Répartition de la population d'Atherigona soccata Rondani (Diptère: Muscidae) et des espèces alliées pendant la saison pluvieuse en Haute-Volta. Agronomie Tropicale, 38, 331-334. BRENIERE, J., 1972. Sorghum shoot fly in West Africa. In Control of Sorghum Shoot Fly, (M.G. Jotwani. and W.L. Young, Eds). (Oxford and I.B.M., New Delhi), pp. 129-135. • CLEARWATER, J.R., 1981. Practical identification of the female of five species of Atherigona Rondani (Diptera: Muscidae) in Kenya. Tropical Pest Management, 27, 303-312.' DAVIES, J.C., SESHU REDDY, K.V. and REDDY, Y.V., 1980. Species of shoot flies reared from sorghum in Andhra Pradesh, India. Tropical Pest Management, 26, 258-261. DEEMING, J.C., 1971. Some species of Atherigona Rondani (Diptera: Muscidae) from northern Nigeria, with special reference ta those injurious ta cereal crops. Bulletin of Entomological Research, 61, 133-190. DEEMING, J.C., 1972. Two remarkable new species of Atherigona Rondani (Dipt., Muscidae) from Nigeria and Cameroun. Entomologist's Monthly Magazine, 108, 3-6• • ' DEEMING, J.C., 1978. New and l ittle known species of Atherigona 36 • Rondani (Dipt., Muscidae) from Nigeria and Cameroun. Entomologist's Monthly Magazine, 114, 31-52. DEEMING, J.C., 198!. New and little known African species of Atherigona Rondani (Dipt., Muscidae). Entomologist's Monthly Magazine, 117, 99-113. DELOBEL, A.G.L. and UNNITHAN, G., 1983. Influence des températures constantes sur les caractéristiques des populations d'Atherigona soccata (Diptères, Muscidae). Acta Oecologia and Applicata, 4, 351-368. DOHAREY, K. L., SRIVASTAVA, B.G., YOUNG, M.G. and DANG, K., 1977. Effect of temperature and humidity on the development of Atherigona soccata Rondani. Indian Journal of Entomology;39, 211-215 DOUMBIA, Y.O. and GAHUKAR, R.T., 1986. Atherigona soccata Rondani et • autres mouches nuisibles au sorgho au Mali. Agronomie Tropicale, 41, 170-172. ECKENRDDE, C.J. and ARN, H., 1972. Trapping cabbage maggots with plant bait and allyl'isothiocyanate. Journal of 'Economie Entomology, 65, 1343-13~5. GAHUKAR, R.T., 1985. Some species of Atherigona (Diptera: Muscidae) reared from Gramineae in Sénégal. Annals of Applied Biology, 106, 399-403. GAHUKAR, R.T., 1987. Population dynamics of sorghum shoot fly, Atherigona soccata (Diptera: Muscidae) in Sénégal. Environmental Entomology, 16, 910-916 JOBIN, L.J., 1985. Development of a large capacity Pheromone trap for Monitoring forest insect pest populations. In Proceeding of the • CANUSA Spruce Budworm Research Symposium, (C.J. Sanders, R.W. 37 • Stark, E.J. Mullins and J. Murphy, (Eds.), Bangor, Maine, September 16-20, 1984, pp. 243-245. NATARAJAN, K. and S. CHELLIAH, 1983. A new method to control sorghum shoot fly. Pesticides, 17, 37. NWANZE, K.F., 1988. Distribution and seasonal incidence of some major insect pests of sorghum in Burkina Faso. Insect Science and its Application, 9, 313-321. SESHU REDDY, K. V. and DAVIES, J .C., 1978. Attractant traps for the assessment of sorghum shoot fly, Atherigona soccata Rondani populations. Bulletin of Entomology, 19, 48-51 STARKS, K.J., 1970. Increasing infestation of the sorghum shoot fly in experimental plots. Journal of Economie Entomology, 63, 1715· 1716 . STEEL, R.G.D. and TORRIE, J.H. 1980. Principles and procedures of • statistics, A biometrical approach, McGrall-Hill Book Company, New York, 633 pp. TANEJA, S.L. and LEUSCHNER, K., 1986. A simple trap for monitoring sorghum shoot fly. Indian Journal of Plant Protection, 14, 83­ 86. YOUNG, W.R., 1981. Fifty-five years of research on the sorghum shoot fly. Insect Science and its Application, 2, 3-9. ZONGO, O.J., 1987. Entomologie du sorgho et mil. In Rapport de synthèse de la campagne 1986. M.A.E., D.A. Service Protection des Végétaux, (Burkina Faso: Laboratoire de Recherches Bobo­ Dioulasso), pp. 1-3 . • • 38

3.7. TABLES •

• • 39

Table 2. Atherigona spp. catches in four trap models in Burkina Faso, 1988 and 1989

Trap Farako-Bâ, 1988 Matourkou, 1989 model No. shoot flies Mean' No. shoot fl ies Mean'

Water trap 32161 8040' 10028 2507' Multi-Pher 25336 6334' 1511 377' ICRISAT 14978 3745' 449 112' • Conical 4459 1115' 349 87'

1 L.S.O ~1547; , L.S.O- 178; P ~ 0.05.; means with the same letter are not significantly different.

• .. 40

Table 3. Sorghum shoot fly Atherigona soccata (male + female) catches in four trap models in Burkina Faso 19BB, 19B9

Trap Farako-Bâ 1988 Matourkou 1989 model No. A. soccata Mean' No. A. soccata Mean'

Water trap 891 223' 718 180' • Multi-Pher 1214 304' 340 85' ICRISAT 740 185' 113 28' Conical 386 97' 51 13'

1 L.S.O .74; 'L.S.O • 43; p. 0.05; means with the sameletter are not significantly different.

• 41 Table 4. Relative abundance of Atherigona and Acritochaeta males captured in • Burkina Faso 1988, 1989 Percentage of total seasonal captures

New Sor9hum shoot Farako-Bâ 1988 Matourkou 1989 Mention in fly species Burkina Faso

Atherigona aberrans Malloch 2.10 1.24 yes Atherigona africana Deeming 0.36 s Atherigona albistyla Deeming 2.28 2.36 l.r Atherigona bimaculata Stein 0.98 1 Atherigona budongoana van Emden 7.51 1.58 1.: Atherigona fililoba Deemin~ 0.76 0.18 yes Atherigona gabonensis Deemlng 0.08 yes Atherigona gilvifolia van Emden 0.03 yes Atherigona hriseiventris van Emâ&n 0.03 yes Atherigona ancocki van Emden 0.32 0.70 ..' Atherigona hyalinipennis van Emden 0.47 0.52 yes Atherigona insignis Deeming 1.19 1.84 • Atherigona lineata Adams 4.75 4.74 1.' Atherigona longifolia van Emden 0.65 2.12 1 Atherigona marrinifolia van Emden 3.59 2.80 1.' Atherigona med eri Deeming 0.08 r.~s Atherigona mirabilis Deeming 2.65 1.32 Atherigona naqvii Steyskal 0.69 0.70 1 Atherigona nigeriensis Deeming 0.03 • Atherigona nigr~iCalis Deeming 0.52 yes • Atherigona occi entalis Deeming 14.85 29.97 1 Atherigona pallidipleura Deeming 2.79 0.62 1.' Atherigona pedunculata van Emden 3.16 0.08 1.' Atherigona ponti Deeming 0..03 0.78 Atherigona pulla Wiedemann 0.39 0.26 r.~s Atherigona rubricornis Stein 0.29 0.18 Atherigona ruficornis Stein 0.03 r.~s Atherigona samaruensis Deeming 1.77 0.36 Atherigona secrecauda Séguy 3.23 7.02 1.' Atherigona soccata Rondani 32.0 19.63 1.' Atherigona tomentigera van Emden 5.63 18.22 1.- Atherigona truncata van Emden 4.03 0.62 1.' Atherigona valida Adams 0.07 1.' Atherigona (s.s.) sp. n. 0.76 0.08 r.~s Acritochaeta orientalis Schiner 2.10 1.24 Acritochaeta yorki Deeming 0.03 yes Total 2753 1141

l Mentioned in Bonzi and Gahukar (1983) • • Mentioned in Bonzi (1981) •• • 42

Table 5. Time required to collect and count shoot flies from four trap models in the field, Burkina Faso, 1988

Ti me (min.) for counting

Trap Without 1 Counting' Total insects Atherigona model counting all insects captured spp. Atherigona spp. including Atherigona spp.

Water trap 32 80 1315 40.22 Multi-Pher 28 43 606 82.04 • 1CR15AT 9 13 221 80.54 Coni cal 4 5 48 56.25

Mean of four counts. Mean of two counts .

• 43 • Table 6. Adult shoot f1 ies (Atherigona spp.) monthly captures, rainfall and relative humidity in southwestern Burkina Faso.

Farako-Bâ 1988 Matourkou 1989 Month Rainfail R.H. No. Rainfall R.H. No. (mm) (%) shoot- (mm) (%) shoot- flies flies captured captured

January 25.2 29.2 February 18.9 15.3 March 3.8 31.5 25.1 27.1 April 56 48.4 10 46.6 May 83 56 59.4 51.0 June 98.5 69 126.3 63.9 • July 193.8 77.4 840' 155.1 73.7 August 195.8 80.43 22218 365.6 90.3 3951 September 305.3 78.3 40745 144.2 77 .1 6824 Octaber 62.5 64.8 12446 40.8 65.6 1449 November 50 685' n.a. n.a. 124'

Catches of 1 week. , Catches of 2 weeks

n.a. E Not available. • • 44

CONNECTING STATEMENT

Appropriate sampl ing techniques are essential to IPM programs because they provi de informatien on the crop. and insect pest under study and allowing recommendations for intervention (Boivin and Vincent 1983). In chapter 3, adult shoot fly population densities were evaluated by trapping with defined peak captures. It is well • established that damage caused by the shoot fly is a function of its population densities (Gahukar 1987). Knowing the fluctuation of adult shoot fly populations, it becomes necessary to assess eggs by sampling in order to improve recommendations in controll ing the pest before -~ damage. Sequential sampling is an important technique in IPM prograll)s, allowing time and money saving (Krebs 1989). Time-sequential sampling, a new use of sequential sampling, allows timely decisions and reduces trips to the field (Pedigo and van Schaik 1984). This chapter deals ,with time-sequential sampling for the sorghum'shoot fly based on egg and dead heart counting •

• .---' • 45

4 TIME-SEQlIENTIAL SAMPLING OF SORGHUM SHOOT FLY. ATHERIGONA SOCCATA • RONOANI (DIPTERA: MUSCIDAE). IN BURKINA FASO.

In press in Insect Science and its Application • Authors: Joanny O. ZONGO. Charles VINCENT. and Robin K. STEWART 46 • 4.1. ABSTRACT Field experiments were conducted in 1988 and 1989 in sorghum fields at three localities near 80bo-Dioulasso (Burkina Faso), West Africa. Eggs and dead hearts were sampled every fifth day starting 10 days after sowing. The second and third leaves of sorghum plants were preferred for oviposition. The maximum number of eggs laid per plant and per leaf were three and two, respectively. The distribution of eggs was random in most (38 out of 39) sampling dates. Pooling data by year (n = 16), the coefficients of correlation between average egg

number and average dead hearts were r = 0.89, 0.87, and 0.80 at Matourkou, Sogossagasso, and Darsalamy, respectively. A time­ sequential sampling plan based on the POISSON distribution was establ ished for the sorghum shoot fly, Atherigona soccata Rondani • (Diptera: Muscidae) using eggs and dead hearts.

• 47 • 4.2. INTRODUCTION The sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), is a key limiting factor of sorghum, Sorghum bic%r (Linné, Moench), production in the wetter southern zones of Burkina Faso, particularly when rainfall dictates delay planting (Brenière 19ï2; Bonzi 1981). In southern Burkina Faso, high shoot fly damage (15-46% dead hearts) has been recorded in farmers' fields (Nwanze, 1988). Sorghum shoot fly research focused on various management practices, including the use of systemic insecticides, cultural control, and the release of high yielding resistant varieties (Young 1981). However, a complete Integrated Pest Management (IPM) program is yet to be developped. Sequential sampling is an important step forward in the development of IPM programs (Boivin and Vincent 1983). In sequential • sampling schemes, sample size is not fixed in advance, resulting in considerable savings in time and money (Krebs 1989). The number of samples required may thus be reduced by 47-63% (Wald 1947) or, in sorne cases, up to 79% (Pieters and Sterl ing 1974). Sequential sampl ing plans have been published for many pests (Pieters 1978). Pedigo and van Schaik (1984), developed and used a time-sequential sampling plan based on the fact that number of insects have characteristic distributions in time, as well as in space. This approach is valuable in studying populations which may be sporadic, or build up rapidly, and decl ine before the end of the season. It allows decisions to be made as to when to sample in the season,' and when to el iminate entire sampl ing periods. Compared to a fixed program of nine sampling periods, Pedigo and van Schaik (1984) found savings of 44 to 67% of resources for the •• green cloverworm, P7athypena scabra (F.), whose outbreaks occur 48 • sporadically in Iowa, U.S.A .. Sorghum shoot fly populations and damage vary with environmental factors, plant varieties, and plant phenological stage (Bonzi 1981, Brenière 1972, Gahukar 1987, Jotwani et al. 1970, Nwanze 1988, Rai et al. 1978, Zongo et al. 1991). Shoot fly damage is usually low « 10%) for early sowings in Burkina Faso (Nwanze 1988) making A. soccata a sporadic pest at this time. Therefore, time-sequential sampling is appropriate for this pest. Delobel (1981) worked on the distribution of sorghum shoot fly eggs in the laboratory and in field conditions using small plots at Nairobi and Mbita, Kenya. He found, on 21 sample occasions, that the distribution of eggs within the field was consistentlya POISSON, although about half of these distributions also agreed with the Negative Binomial. No sequent ial sampling plans have been yet publ ished for the • sorghum shoot fly, and the present investigations were undertaken to establish a time-sequential sampling plan for this pest. 4.3. MATERIALS AND METHODS Experiments were conducted in 1988 and 1989 at Matourkou, Darsalamy and Sogossagasso in sorghum fields (60 x 40 m) located ca. 10 , 15 and 35 km from Bobo-Dioul asso (11°11 'N, 4°18'W), respectively. At Darsalamy and Sogossagasso farmers' fields were used while the field at Matourkou was located in a research station. The local. sorghum variety "Gnofing" was sown on 12, 13 and 14 July, one month after normal planting dates-respectively, at Matourkou, Sogossagasso and Darsalamy. Inter-row and intra-row were 0.80 m and 0.40 m, respectively. Fields were fertilized with 200 kg/ha of NPK (15-15-15) appl ied in two occasions, (namely 100 kg/ha at sowing time, '-...-.1" " • 100kg/ha 30 days after sowing). Fifty kg/ha of urea (46%) were applied 49 • 45 days after sowing. In each field, samples were taken on eight occasions, every fifth day, starting 10 days after planting. On each occasion, sorghum shoot fly eggs were counted on 30 randomly selected plants. Each plant was carefully inspected; the position of each egg and the number of leaves were noted from top to bottom. The number of eggs per leaf was also recorded. Dead hearts were counted on 100 randomly selected plants. Departure from a random dispersion was tested for each local ity and year by using the following method:

ID= S2 (n-1)/X, where ID is the index of dispersion, where S2 = variance, n is the number of samples, and X= mean number of eggs or dead hearts (Krebs 1989). The Chi-square x2 (with n-1 df) was used to test the observed dispersion. There were 29 df for eggs and 99 • for dead hearts. If a data set followed the 'POISSON distribution, the value of ID lied within the limits /0.975 and /0.D25.The standardized

Morisita index of dispersion (Ip ) (Smith-Gill 1975) ranging from -1.0 to +1.0, with 95% confidence limits was used to calculate the di spersi on when a val ue of ID l ay outside the l imits defined previ ously.

Arandom pattern gave Ip of zero. Aggregated and regul ar pattern occured

when Ip was above and below zero respectively (Krebs 1989). To calculate the time-sequential sampling parameters, data of all local ities were pooled. The main parameters required for POISSON distribution were:

hl = log [B1(1 - a) ]

h2 = log [(1 - BI) a]; • • 50

where h, and h2 are intercepts, llIoi = mean number of the eggs or dead hearts expected in the ith sample of an endemic population, m'i= mean number of the eggs or dead hearts expected in the i th sampl e of an outbreak population, bt is a slopelike parameter, Wi is a weighting coefficient, dt is a weighted cumulative number of eggs or dead he arts

observed, ri is the number of eggs or dead hearts in the i~ sample, Q is probability of calling a population endemic wh en it is outbreak, and B is probability of calling a population outbreak wh en it is endemic. The boundaries of the decision zones after the t~sample are calculated • as follows: d't= h,+ bt (lower limit) d2t = h2+ bt (upper limit) The class limits (m., m,) on each sampling data describing endemic and outbreak populations were determined using pooled data from the three localities and the two years. Because economic injury levels vary from one cultivar to another (Rai et a7. 1978), and that no formal economic injury level has yet been published for sorghum growing in West African conditions, we used a nominal threshold based on unpublished work that we conducted at Matourkou, Bobo-Dioulasso from 1988 to 1990 (Table 7).

The level of acceptable error was set at 0.1 for both Q and B, as • recommended by Waters (1955). 51 • 4.4. RESULTS Sorghum shoot fly females laid their eggs mostly on the second (40.48%) and third (50.28%) leaves (Table 8). The maximum number of eggs laid per plant and per leaf were three and two, respectively. Seasonal average number of eggs per plant and percent of dead hearts were greater in 1988 than in 1989 at Matourkou and Sogossagasso (Table 9, 10). Four times out of S, the peak number of eggs and the average peak of dead hearts coincided on the same sampling date. In 1989, peak number of eggs and dead hearts occurred on the 7th sampling date in all localities (Table 9, 10). The distribution pattern of eggs was random in most (38 times over 39) sampling dates. An aggregated pattern occurred at Matourkou on August 6th, 1989 (Table 9). The dispersion patterns of dead hearts were random (38 times over 42), and regular (4 times over 42) (Table • 10). In Sogossagasso, the dispersion pattern of both eggs and dead hearts was consistently random in 1988 and in 1989 (Table 9, 10). In Darsalamy, the dispersion pattern of eggs was random, whereas dead hearts were randomly distributed on six sampling dates and regularly distributed on one occasion (Table 9, 10). Using pooled data (by date) of the two years, the distribution of eggs was random in the three localities, whereas dead hearts were randomly distributed in Sogossagasso and Darsalamy; and randomly and regularly distributed in Matourkou. A positive significant ~ ~ 0.05) correlation (r • 0.87, n- 48, all years and localities pooled) has been found between egg abundance and dead hearts, the regression equation being Y• -1.34S7e-2 + 0.9420Sx. The coefficient of correlation and regression equation (n • • IS, all years pooled for each locality) were: r = 0.89, Y= -3.170Se-2 52 • + 1.0487x for Matourkou; r = 0.87, Y = -6.1350e-3 + 0.87603x for Sogossagasso, and r = 0.80 ,Y= 6.9524e-3 + 0.76155x for Darsalamy. We chose a tabular presentation (Table 11, 12) for the time­ sequential sampling plan as Pedigo and van Schaik (1984) found this format most convenient. 4.5. DISCUSSION The second and third leaves were preferred for oviposition. Our results agree with Ogwaro (1978), who found that 28.5 and 54.1% of total eggs were deposited on the second and thir~ leaves, respectively. After hatching, the first instar larva takes one to six hours to reach the base of the leaf sheath (Doggett 1988). Because eggs are preferentially laid on second and third leaves, first instar larvae are near the site of penetration in the main shoot; this reduces exposure to natural enemies and adverse climatic conditions. Although Ogwaro • (1978) recorded a few eggs on the sixth and the seventh leaves, we found no eggs wh en the sorghum plants had more than five leaves. Ogwaro (1978) pointed out that the lower leaf surfaces were preferred for oviposition, which we also observed. Our results on egg distribution confirm Delobel's (1981) finding that the distribution of sorghum shoot fly eggs is random or slightly aggregated. Aggregated distribution occurred occasiorally when many plants bore more than one egg. The biological consequence of such a distribution is that many larvae hatching from these eggs will perish as usually only one larva develops in a single shoot (Delobel, 1981). Dead hearts caused by the sorghum shoot fly were frequently randomly distributed and, on few occasions, regularly. In 1988, average dead hearts were higher in Matourkou (research station) than in • Sogossagasso and in Darsalamy. ICRISAT (1983, 1984) and Nwanze (1988) 53 • found similar differences in infestation level and pointed out that this is due to different varieties and sowing dates. However, in 1989 the percentage of dead hearts was higher in Darsalamy (31%) than in Matourkou (14%). We observed 22% dead hearts in Sogossagasso on August 17th, 1988 whereas Nwanzc (1988) found 26% in the same locality (unknown sampling date). However, the percentage of de ad hearts were much lower (6%) in 1989 at Sogossagasso. Rainfall and relative humidity are important factors for sorghum shoot fly population outbreaks (Naitam and Sukhani 1985, Gahukar 1987). Zongo et al. (1991) noted that rainfall and relative humidity were higher in 1988 than in 1989 with, as a consequence, a higher shoot fly infestation level in 1988. The seasonal variation in oviposition and dead heart prevalence observed in our study is thus partly due to climatic conditions. Similar seasonal variation in oviposition and • dead heart have been reported by Gahukar (1987), and Jotwani et al. (1970). Time-sequential sampling is intended to address the problem of when samples should be taken in the season (Pedigo and van Schaik 1984). For the sorghum shoot fly, sampl ing efforts should coyer the early stage of sorghum seedlings, as Rai et al. (1978) found that early attack leads to complete destruction of the plar.ts. In addition, Jotwani et al., (1970) found that the most susceptible stage for infestation is within 21 days after germination. Sampling dead hearts as an early detection method does not allow . - enough time to plan and implementcontrol actions in due time. However, our sequential sampling plan may prove to be useful for rapid survey of shoot fly damage. In general, control measures should be taken before .' dead hearts formation. Therefore, egg sampling is most appropriate in 54 • an IPM context. This approach allows sufficient time to undertake controi actions as Barry (1972) found that eggs hatch within 2-5 days after oviposition and dead heart formation occurs 2-3 days after hatchi ng. An effective management program of the sorghum shoot fly should be adapted to local conditions. Whatever the agronomie conditions, egg sampling should be used as a monitoring technique to alert farmers of threatening population levels.

e

• 55 • 4.6. REFERENCES Barry, D. 1972. Notes on life history of a sorghum shoot fly, Atherigona varia soccata. Ann. Entomo7. Soc. Am. 65, 586-589. Boivin, G. and Vincent, C. 1983. Sequential samplin9 for pest control programs. Agriculture Canada, Technical Bulletin 1983-14Ei Agriculture Canada, Research station, Saint-Jean-sur-Richelieu, Québec, Canada. 29 p. Bonzi, S.M. 1981 Fluctuations saisonnières des populations de la mouche des pousses de sorgho en Haute-Volta. Insect Sei. App7ic. 2, 59-62. Brenière, J. 1972. Sorghum shoot fly in West Africa, pp. 129-135, In Contro7 of sorghum shoot f7y, (Jotwani, M.G. and W.L. Young Eds). Oxford and I.B.M., New Delhi . Delobel, A.G.L. 1981. The distribution of the eggs of the sorghum • shootfly, Atherigona soccata Rondani (Diptera: Muscidae). Insect Sei. App7ic. 2, 63-66. Doggett, H. 1988. Sorghum. Longman Scientific &Technical, Harlow U.K. pp. 301-306. Gahukar R.T. 1987. Population dynamics of sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), in Senegal. Environ. Entomo7. 16, 910-916. International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) 1983. Annua7 Report 1982, International Cooperation, Patancheru, India, pp. 363-365. International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) 1984. Sahe7ian Center Annua7 Report 1983, Entomo7ogy, ICRISAT Niamey, Niger, pp. 31-37 . • Jotwani, M.G., Marwaha, K.K., Srivastava, K.M. and Young, W.R. 1970. 56 • Seasonal incidence of shootfly (Atherjgona varja soccata Rond.) in jowar hybrids at Delhi. Indjan. J. Ent. 32, 7-15 Krebs, C.J. 1989. Ecological methodology. Harper &Row Publishers, New York. 654 p. Nait"m, N.R. and Sukhani, T.R. 1985. Ovipisition behavior of the sorghum shootfly Atherjgona soccata Rondani under different soil, plant and weather parameters. Indjan J. Ent. 47, 195-200 Nwanze, K.F. 1988. Distribution and seasonal incidence of sorne major insect pests of sorghum in Burkina Faso. Insect Scj. App7jc. 9, 313-321. Ogwaro, K. 1978. Ovipositional behaviour and host-plants preference of the sorghum shootfly, Atherjgona soccata (Diptera: Anthomyiidae). Entom07. exp. app7. 23, 189-199 . Pedigo, L.P. and van Schaik, J.W. 1984. Time-sequential sampling: Anew • use of the sequential probability ratio test for pest management decisions. Bu77. Ent. Soc. Am. 3D, 32-36. Piet<;lrs, E. P. 1978. Bibliography of sequential sampling plans for insects. Bu77. Ent. Soc. Am. 24, 372-374. Pieters, E. P. and Sterling, W.L. 1974. Asequential sampling plan ~or the cotton leafhopper, Pseudatomosce7js' serjatus. Envjron. Entom07. 3, 102-106. Rai, S., Jotwani, M.G. and Jha, D. 1978. Economic injury level of shootfly, Atherjgona soccata (Rondani) on sorghum. Indjan J. Ent. 40, 126-133. Smith-Gill, S.J. 1975. Cytophysiolog~ca1 basis of disruptive pigmentary patterns in the leopard frog Rana pjpjens II. Wild type and mutant cell specific patterns. J. Morph. 146, 35-54 • • Wald, A. 1947. Sequential analysis. Dover Publications, INC. New York. 57 • 212 p. Waters, W.E. 1955. Sequential sampling in forest insect surveys. For. Sci. l, 68-79. Young, W.R. 1981. Flfty-five years of research on the sorghum shoot fly. Inseet Sei. App7ie. 2, 3-9. Z.:Jngo, J.O., Vincent, C. and Stewart, R.K. 1991. Monitoring adult sorghum shoot fly Atherigona soeeata (Rondani) (Di ptera: Muscidae), and related species in Burkina Faso. Trop. Pest Manag. 37, 231-235 . •

• • 58

4.7. TABLES •

• • 59

Table 7. Endemie (~) and (m,) outbreak population configurations of Atherigona spp. eggs (n=30) and dead hearts (n=100), Burkina Faso.

Sample Days Eggs Dead hearts date after sowing m• m, m. m,

1 10 2 6 4 10 2 15 3 8 7 12 3 20 5 10 10 14 • 4 25 7 13 12 17 5 30 9 15 13 19 6 35 12 17 15 20 7 40 13 19 16 21 B 45 5 7 B 15

•• • 60

Table 8. Sorghum shoot fly egg distribution on leaves in three 10ca1ities,

1 Number of times eggs were deposited on the leaf•

•

62 Tabl e 10. Mean (n= 100), vari an ces , and di spersi on characteristi cs of dead • hearts caused on sorghum by Atherigona spp. in three localities, Burkina Faso. 1988 1989

Locality x 10 x 10 Sampling period

Matourkou July 22 0.00 0.00 0.00 0.00 0.00 0.00 July 27 0.00 0.00 0.00 0.00 0.00 0.00 August 1 0.03 0.029 95.04' 0.02 0.019 94.05" August 6 0.15 0.128 84.15' 0.04 0.036 89.10" August Il 0.45 0.250 54.45" 0.06 0.052 85.14' August 16 0.58 0.240 40.59" 0.08 0.072 89.10' August 21 0.37 0.230 61.38" 0.14 O.lIs 81.18' August 26 0.07 0.062 87.12' . 0.05 0.044 87.12' Sogossagasso July 23 0.01 0.010 99' 0.01 0.10 99' July 2B 0.00 0.00 0.00 0.02 0.019 94. os" August 2 0.01 0.010 99' 0.03 0.029 95.04' • August 8 0.12 0.102 84.15' 0.02 0.019 94. os" August 12 0.18 0.144 79.20' 0.05 0.044 87.12' August 17 0.22 0.168 75.24' 0.04 0.036 75.24' August 22 0.08 0.072 89.10' 0.06 0.052 85.14' August 27 0.02 0.019 94.05" 0.02 0.019 94.05' Darsalamy July 24 0.02 0.019 94. OS' 0.00 0.00 0.00 July 29 0.04 0.036 89.10' 0.01 0.010 99' AU9ust 3 0.02 0.019 94. OS' 0.03 0.029 9s.0s" AU9ust 8 0.06 0.052 85.14' 0.03 0.029 9s.0s" August 13 0.13 0.108 82.17' 0.05 0.044 87.12" August 18 0.12 0.102 84.5' 0.26 0.194 73.95' August 23 0.14 O.lIs 81.18' 0.31 0.216 68.31'" August 28 0.05 0.044 87.12' 0.26 0.194 73.95'

, POISSON distribution as 10 lies within the limits 73.46 (/0.915) and 128.31 (/o.m)for 99 df.

" Tests with 10 indicated that these data were not a Poisson distribution; Ip tests suggested a regular pattern as I wa$ -1 in ~latourkou and ·-0.25 in • Darsalamy. p • • •

. Table Il. Time-sequential sampling plan based on egg counts of sorghum shoot fly Atherigona soccata.

a b c d Sample Number Weighting Weighted Lower Total of Upper li/llit number counted factor count l imit weighted count

1 e 0.4771 Stop 3.05 Continue 4.95 Stop 2 0.4259 sampling 4.05 samplillg 5.95 and 3 0.3010 4.05 5.95 apply 4 0.2688 3.05 4.95 treatment 5 0.2218 3.05 4.95 6 0.1512 4.05 5.95 7 0.1648 5.05 6.95 8 0.1461 1.05 2.95

Directions: Sampling should be started from at least 10 days after sowing until 40 days after sowing. Samples are to be taken every fifth day. The number of eggs counted (e) is recorded in column a and then multiplied by the weighting factor (column b). This number is recorded in columns c and d, and compared to the lower or the upper limit. If the number in column d exceeds the upper limit, stop sampling and apply treatment. If the number is below the lower limit, stop sampling. If the number exceeds the lower limlt, continue sampling.

63 • • •

Table 12. Tlme-sequentlal sampllng plan based on dead he art counts caused by the sorghum shoot fly, Atherigona soccata.

a b c d Sample Number Welghtlng Welghted lower Total of Upper llmlt number counted factor count lImlt welghted count

1 e 0.3979 Endemie 5.05 Continue 6.95 Outbreak 2 0.2340 population 4.05 sampllng 5.95 population 3 0.1461 3.05 4.95 4 0.1512 4.05 5.95 5 0.1648 5.05 6.95 6 0.1249 4.05 5.95 7 0.1180 4.05 5.95 8 0.1346 3.05 4.95

Directions: Sampllng should be started from at least 10 days after sowlng. Samples are to be taken every flfth day untll 40 days after sowlng. The number of dead hearts counted (e) Is recorded ln column a and then multlplled by the welghtlng factor (column b). This number Is recorded ln columns c and d and compared to the lower or the upper llmlt. If the number ln column d exceeds the upper llmlt, the population lndlcates an outbreak. If the number Is below the lower llmlt, the population Is endemlc.

64 • 65

CONNECTING STATEMENT

In Chapter 3, the relative abundance and species composition of shoot flies in the field were assessed while chapter 4 provided information on the emergence pattern of shoot fly eggs and damage with a subsequent time-sequential sampling scheme. It is essential to investigate whether changes in shoot fly abundance can be linked with particular cultural practices. Cultural controls, the oldest methods for managing insect pest populations are preventive rather than • curative (Knipling 1979, Hill 1989). They are important in IPM programs, particularly in developing countries where the technical and educational level of farmers is low. Cultural practices such as manipulating sowing dates or intercropping could help to escape attack by the shoot fly. The goal of this chapter is to answer questions on wh en to sow sorghum to escape heavy shoot fly damage. Another hypothesis investigated was whether intercropping sorghum-cowpea could reduce shoot fly damage •

•• • 66

5 Influence of Cultural Practices on Sorghum Yields and Incidence of Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae), in Burkina Faso • •

To be submitted to Sahel Phytoprotection, August 1992. Authors: ZONGO, J.O., STEWART, R.K., VINCENT, C. • 67 • 5.1. ABSTRACT Field experiments were conducted in 1988, 1989 and 1991 in a sorghum field at Matourkou, Bobo-Dioulasso (Burkina Faso), to determine plant spacing arrangements for intercropping sorghum-cowpea, Sorghum bicolor [L.] (Moench)-Vigna unguiculata [L.] Walp., and the most suitable sowing dates and plant densities for avoidance and reduction of yield 10~ses caused by the shoot fly, Atherigona soccata Rondani (Diptera: Ml!~cidae). Observations were recorded on eggs and dead he arts 17 and 28 days after plant emergence respectively. In both 1988 and 1989, intercropping systems gave a LER (Land Equivalent Ratio) higher than one. In 1988 and 1991, no significant differences were observed with respect to the number of eggs laid, the percentage of plants bearing eggs and the percentage of dead hearts. In 1989, significant differences were only observed with respect to dead heart incidence. • Sowi ng dates between June 20 and 30 were acceptable whereas sowi ng dates after June 30 should be avoided. Plant densities were not significant with respect to damage. Significant negative correlation existed between the percentage of dead hearts and the yi~ld in all the five sowing dates, between the yield and the sowing dates, and between the yield and the numbers of tillers.

• 68 • 5.2. INTRODUCTION The shoot fly, Atherigona soeeata Rondani (Diptera: Muscidae), is an important pest of sorghum, Sorghum bieo7or (Linné, Moench), in West Africa (Nwanze 1985, Gahukar 1990), including Burkina Faso (Bonzi 1981, Nwanze 1988). Several species of shoot fly are injurious to sorghum (Deeming, 1971) but in Burkina Faso, A. soeeata accounted for over 96% of the flies reared from sorghum shoots (Nwanze, 1988). Several control strategies have been suggested including insecticide applications, the use of resistant varieties, cultural practices (Young, 1981) and sequential sampiing (Zongo et a7. 1992). Mixed cropping represents 80% of the cultivated area in West Africa (Steiner, 1984). This practice may decrease insect pest populations (Vandermeer, 1989). Compiling the results from 150 • publ ished studi es on the effect of di versi fying agroecosystems on insect pest populations, Risch et a7. (1983) found that 53% of insect pest species (n = 198) were less abundant in the more diversified system, 18% were more abundant in the diversified system, 9% showed no difference, and 20% showed a variable response. Intercropping sorgh~m­ cowpea, Vigna unguieu7ata [L.] Walp. is widely practiced by Burkina Faso farmers, the main advantages being the rational use of land, labour saving and diversified food supply. Cowpea is usually harvested before sorghum and serves as a food supply before regul ar harvest periods. In India, sorghum shoot fly damage was severe when sorghum was intercropped with ground nuts (Venugopal and Palanippan, 1976). In Kenya, Raina and Kibuka (1983) found that intercropping sorghum-maize • in different planting holes or in the same hole did not significantly 69 • affect shoot fly oviposition on either crop. Modifying planting dates is also one of the most widely used methods to cause asynchrony between crops and insect pests. In Burkina Faso, Brenière (1972) evaluated shoot fly damage for three different sowing dates in the west central region (i.e. 5aria, Koudougou) and found that sorghum seedlings were less damaged with early sowing dates. In India, several authors from different localities have studied the effects of sowing dates and seed rates on the incidence of the shoot fly and found that early sowing helped to avoid and reduce damage (Ram et al. 1976, Gandhale et al. 1982, Mote, 1983). To implement sound IPM programs, various tactics have to be investigated. The present investigations were undertaken to determine plant spatial arrangements and the most suitable sowing date and optimum seed rate to avoid losses caused by the shoot fly and to obtain • good yields under Burkinabè conditions. 5.3. MATERIAlS AND METHODS The st~dy was carried out in 1988 and 1989 at Matourkou, located ca. 10 km from Bobo-Dioulasso (l1°lI'N, 4°18'W), Burkina Faso, West Africa. 5.3.1. Experimental Series A: Intercropping Five cropping systems we'"e appl ied in a randomized complete block design with four replicates: 1) 5" pure sorghum; 2) 52' one row of sorghum + one row of cowpea; 3) 53' two rows of sorghum + two rows of cowpea; 4) 5., two rows of cowpea + three rows of sorghum; 5) 55' pure cowpea (Fig. 1). Each plot measured 7.5 x 5 m and contained 10 rows. Row spaci ngs were 0.75 min all plots whereas intra-row spaC'ings were 0.25 and 0.20 mfor sorghum and cowpea respectively. One and two • seedlings were maintained per hill for cowpea and sorghum respectively. 70 • Ten tons/ha of cow dung were applied at plowing time. Plots were fertilized with 200 kg/ha of NPK (15 15 15) applied on two occasions, i.e. 100 kg/ha at sowing time, and 100kg/ha 30 days after sowing. Fifty kg/ha of urea (46%) were applied 45 days after sowing. Cowpea plants were treated with Decise (Procida/Roussel Uclaf, Abidjan, Côte d'Ivoire), deltamethrin EC, 12 9 a.i/ha at 30 and 40 days after sowing to control thrips and pod sucking bugs. The treatment was done with a hand operated sprayer. Weeding was done as required, and earthing-up was carried out at 30 and 45 days after sowing on cowpea and sorghum respectively. Numbers of eggs and dead he arts were recorded at 17 and 28 days after plant emergence respectively. In pure sorghum, observed rows were the fifth and sixth rows. In intercropped sorghum cowpea, they were the second and third rows for 52 and 53' and the third and fourth • for 5. (Fig. 1). On these rows, the total number of plants, plants bearing eggs, eggs, and dead hearts were recorded. At harvest, the first and the last hills on a row of sorghum were discarded. In cowpea rows, 50 cm of row were left on each extremity. Harvesting was do ne on observed rows only. The weight of grain from each plot was recorded. To assess yields from intercropping, the Land-Equivalent-Ratio (LER) (Mead, 1980, 1986) was used. The experiments were repeated in 1991 to augment 1988 and 1989 results on sorghum shoot fly incidence. Both crops were sown on July 26th. No cow dung was applied. The parameters observed were: the number of plants bearing eggs, the number of eggs laid at 17 days after pl ant emergenceand the percentage of dead hearts at 28 days after • plant emergence. 71 • 5.3.2. Experimental Series B: Sowing dates and plant densities Each year (1988, 1989) the local sorghum variety "Gnofing" was sown on five dates at la day intervals, on 20, 30 June and on la, 20, 30 July. The experimental design was a split-plot with four replicates, the main plots being sowing dates and the sub-plots, plant densities. The seeds had been treated with K-Othrine~ (Deltamethrin, 50 g/100 kg of seed) to prevent damage by stored grain pests. Each plot measured 3.20 x 4m and contained four rows. Row spacings were 0.80 m in all densities whereas intra-row spacings were 0.50 m (25,000 hills /ha), 0.40 m (31,250 hills /ha, the recommended density in Burkina Faso), 0.30 m (41,666 hills/ha), 0.20 m (62,500 nills/ha), and 0.10 m (125,000 hills/ha) for densities l, 2, 3, 4 and 5, respectively. Two seedlings were maintained per hill in all plots. Plots were fertilized with 200 kg/ha of NPK (15 15 15) appl ied on two occasions, i.e. 100 kg/ha at • sowing time, and 100kg/ha 30 days after sowing. Fifty kg/ha of urea (46%) were applied 45 days after sowing. Observations were recorded on the plants of the two central rows twenty eight days after seedling emergence. The number of plants, dead hearts, tillers, dead hearts on tillers were counted. At harvest time, the number of plants, main earheads, earheads on tillers and weight of grain were recorded from each plot. Data of both experiments were transformed to arcsin values and analysed using Scheffe's test, SuperAnova (version 1.1 for the Macintosh computer) Abacus Concepts Inc. (1989) .

. ' 72 • 5.4. RESULTS 5.4.1. Series A In both 1988 and 1989, intercropping systems gave a LER higher than 1.00 (Table 13, 14). A value of > 1.00 indicates an agronomic advantage for intercropping. In 1988, the LER was 1.48, 1.30 and 1.28 in 52, 53, S. respectively (Table 13). In 1989, the LER was 1.42, 1.23 and 1.06 in 52, 53, S. respectively (Table 14). In 1988, no significant differences were observed with respect to the number of eggs laid, the percentage of plants bearing eggs and the percentage of dead hearts (Table 15). In 1989, significant differences were only observed with respect to dead heart incidence (F = 4.37, df= 3,12, P < 0.026) (Table 15). In 1991, no significant differences were observed with respect to all measured parameters (Table 15) . 5.4.2. Series B • Shoot fly damage ranged from 6.47 to 66.89% dead he arts in 1988, and from 10.20 to 45.38% in 1989 (Table 16). Si9nificant differences were observed among sowin9 dates. No significant di fferences were observed for plant density and for the interaction of sowing dates­ plant density. In 1988 the percentage of dead hearts was higher than in 1989 (Table 16). There were significant negative correlations between the yield and the percentage of dead hearts in all the five sowin9 dates, the yield and the sowing dates, and between the yield and the numbers of tillers. The regression equations for yields (y) versus dead hearts (x) were (n = 100, all sowing dates pooled) y = - 0.033x +

2.83 (r = 0.78), and y = - 0.019x + 1.40 (r = 0.72) in 1988 and in 1989 respectively. The regression equations for yields (y) and sowing dates (x, expressed in Julian calendar) were y = - 0.99x + 1 (r = 0.89) • in 1988 and y = - 0.87x + 1 (r = 0.69) in 1989 respectively. The 73 • regression equations for yield (y) and tillers (x) were y : - 0.71x + 1 (r : 0.69), y : - 0.74x + 1 (r : 0.71), in 1988 and in 1989 respectively. Few plants (32 of 3730 plants in 1988 and Il of 2236 plants in 1989) bore more th an one earhead and no earheads were recorded on tillers. 5.5. DISCUSSION Our results on the LER values suggest an agronomic compatibility between the local sorghum cultivar "Gnofing" and the cowpea cultivar TVx 3236. At Farako-Bâ (c~ 2 km from Matourkou), Muleba (1984, 1985) reported a LER value of 0.95 and 1.02 in 1984 and 1985 respectively in the intercropping sorghum (cultivar "Framida") and cowpea (Cultivar TVx 3236). He found that the LER varied according ta cowpea cultivars and that yields of bath sorghum and cowpea were significantly reduced in • certain cultivars. He also noted that cowpea was more competitive than sorghum in using sail nutrients. Our 1988 and 1991 results on shoot fly incidence are similar ta those of Dissemond and Hindorf (1990) who did not find significant differences between pure sorghum and intercropped sorghum-cowpea sown in intra-row spacings. Shoot fly infestation was higher in 1988 than in 1989. This may be due ta more favorable climatic conditions for the shoot fly in 1988 (Zongo et al. 1991). Our results suggest that intercropping sorghum-cowpea has no significant effect in reducing shoot fly damage. This confirms Raina and Kibuka's (1983) conclusion that crops such as cowpea which sustain high aphid populations constitute a poor choice for intercropping with sorghum. However, intercropping systems.should not only be based on • pest. control objectives but should also focus on obtaining good yields. 74 • Steiner (1984) described typical traditional cropping systems and reviewed the agronomic and socio-economic aspects of intercropping in West Africa. He concluded that intercropping has a positive impact in small holder farming systems, but recommendations cannot be formulated as easily as for single crops because of the complexity of intercropping. Our results on the incidence of the shoot fly, indicated an increased infestation with later sowing dates. Our observations are similar to those of Brenière (1972), Gandhale et a7. (1982), and Mote (1983). Brenière (1972) pointed out that the earliest sown plants escaped severe damage but this would change according to the year. The significant negative correlation between grain yields and dead hearts here reported are in agreement with those of Rai et a7 . (1978) and Mote (1988). Mote (1983) observed that for each per cent • increase in dead hearts, a reduction in grain yield of 32.28, 65.56, 62.06 kg/ha is obtained in early, normal and delayed sowing respectively. Rai et a7. (1978) and Mote (1988) found that the reduction in grain yield is dependent on the sorghum varieties. Our results on the effects of plant density (seed rates) on the incidence of the shoot fly are similar to those of Sukhani and Jotwani (1980), and Mote (1983). However, they are in strong contradiction to those of Ayyar (1932) and Ponnaiya (1951) who recommended control of the shoot fly by using high seed rates and then removing and destroying damaged plants. Brenière (1972) also recommended this method in west Africa. In Burkina Faso, this technique of removing and destroying damaged plants may entail much labor particularly at the beginning of the rainy season. Although it may be practiced, it is unsuitable • because farmers have a time c~mmitment to other crops (such as cash 75 crops) at that period. • Delobel (1984) and Blum (1972) indicated that some sorghum varil:ties such as CSH-1 produce ti11ers that may bear earheads and so compensate for the shoot fly attack . Our results on the local cultivar "Gnofing" are not in agreement with these observations as no tillers bearing earheads were produced and there was a negative correlation between yield and number of tillers. This confirms Panchabhavi et al. (1989) finding that tiller formation does not compensate for grain and fodder yield losses. In Burkina Faso, the economic situation dictates that pest control approaches be based on practices easily understood and carried out by farmers. Sowing sorghum at the beginning of the rainy season results in. reduced shoot fly damage. Sowing dates prior to June 20 could be preferable. Sowing dates between 20- 30 June may also be • practiced. To be more effective, this simple cultural practice requires . united.action by a11 farmers from the same l ocal ity. Young (1981) recommended that the sorghum crop should be sown within a period of 2-3 weeks in any defined area.

• 76 • 5.6. REFERENCES Abacus Concepts Inc. 1989. SuperANOVA, Accessible General Linear Modeling, Berkeley, California, 316 p. Ayyar, T.V.R. 1932. Entomology of the sorghum plant in south India. Madras Agricultural Journal, 20: 50. 8lum, A. 1972. Sorghum breeding for shoot fly resistance in Israel, pp. 180-191. In Control of sorghum shoot fly, Jotwani, M.G and Young,

~ W.R. (eds.). Proceeding of International Symposium 1-3 November 1971, Hyderabad. Oxford &IBH Publ. India, New Delhi. Bonzi, S.M. 1981. Fluctuations saisonnières des populations de la mouche des pousses de sorgho en Haute-Volta. Insect Science and its Application, 2: 59-62. 8renière, J. 1972. Sorghum shoot fly in West Africa. pp. 129-135, In Jotwani, M.G. et W.L. Young (Eds.) Control of sorghum shootfly. • Oxford and I.B.M., New Delhi. Deeming, J. C. 1971. Some species of Atherigona Rondani (Diptera: Muscidae) from Northern Nigeria, with special reference to those injurious to cereal crops. Bulletin of Entomological Research, 61: 133-190. Delobel, A. 1984. Une méthode d'estimation des pertes de récolte attribuables à la mouche du sorgho, Atherigona soccata Rondani. Agronomie Tropicale, 39: 350-354. Dissemond A., Hindorf H., 1990. Influence of sorghum/maize/cowpea intercropping on the insect situation at Mbita/Kenya. J. Appl. Entomol., 109: 144-150. Gandhale,D.N., G.N. Salunkhe and L.M. Naik 1982. Indian Journal of Plant Protection, 10: 67-69 • • Jotwani, M.G. 1981. Integrated approach to the control of the sorghum 77 • shootfly. Insect Science and its Application, 2: 123-127. Mead R., 1980. The concept of a 'Land Equivalent Ratio' and advantages in yields from intercropping. Exp. Agric., 16: 217-228. Mead R., 1986. Statistical Methods for multiple cropping. In Multiple cropping systems, FRANCIS (ed.). MacMillan Pub1ishing Company, New York, p.317-350. Mi ni stère de l'Agri cul ture et de l' Ei evage du Burkina Faso 1988. Statistiques Agricoles Campagne 1987-1988. Mote, U.N. 1983. Relation between the shootfly damage and sorghum yields during rainy season. Indian Journal of Plant Protection, 11: 145-147. Mote, U.N. 1988. Correlation between the dead hearts caused by shootfly Atherigona soccata Rondani and the yield of sorghum hybrids . Indian Journal of Entomology, 48: 356-357. • Muleba N., 1984. Agronomie du niébé. In SAFGRAD (Semi-Arid Food Grain Research and Development), Rapport annuel, Ouagadougou, Burkina Faso, p. EI-E68. Muleba N., 1985. Agronomie du niébé. In SAFGRAD (Semi-Arid Food Grain Research and Development), Rapport annuel, Ouagadougou, Burkina Faso, p. EI-E73. Nwanze, K.F. 1985. Sorghum insect pesis in West africa pp. 37-43, In International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). Proceedings of the International Sorghum Entomology Workshop, 15-21 July 1984. Texas A & M University, College Station, TX, USA. Patancheru, A.P. 502324 India: ICRISAT. Nwanze, K.F. 1988. Distribution and seasonal incidence of sorne major insect pests of sorghum in Burkina Faso. Insect Science and its .' Application, 9: 313-321. 78 • Nwanze K.F., 1988. Distribution and seasonal incidence of sorne major insect pests of sorghum in Burkina Faso. Ins. Sci. Appl ic., 9: 313-321. Panchabhavi, K.S., K.A. Ku1karni, P.C. Hieremath and R.K. Hegde 1989. A study on the yield compensation by tillers caused by shootfly in sor~hum. Karnataka Journa7 of Agricu7tura7 Science, 2: 338­ 340. Ponnaiya, B.W.X. 1951. Studies on the genus sorghum. 1. Field observations on sorghum resistance to the insect pest. Atherigona indica M., Madras University Journa7, 21: 203-217. Raina A.K., Kibuka J.G., 1983. Dviposition and survival of the sorghum shootfly on intcrcropped maize and sorghum. Ento. exp. appl. 34: 107-110 . Ram, S., D.P. Handa and M.P. Gupta 1976. Effects of planting dates of • fodder sorghum on the incidence of shootfly, Atherigona soccata Rond. Indian Journa7 of Entomo7ogy, 38: 290-293. Risch S. J., Andow D., Altieri M.A., 1983. Agroecosystem diversity and pest control: data, tentative conclusions and new research directions. Environ. Entomol., 12: 625-626. Sukhani, T.R. and M.G. Jotwani 1980. Comparison of cultural and chemical methods for the control of sorghum shoot fly. Entomo7ogy, 5: 291-294. Vandermeer J. H., 1989. The ecology of intercropping. Cambridge University Press, New York, 237 p. Venugopal M.S., Pal anippan S., 1976. Infl uence of intercropping sorghum on the incidence of sorghum shoot fly. Madras Agric. J., 83: • 572-573 . 79 • Young, W.R. 1981. Fifty-five years of research on the sorghum shootfly. Insect Science and its Application, 2: 3-9. Zongo J.O., Vincent C., Stewart R. K. 1991. Monitoring adult sorghum shoot fly Atheri gona soccata Rondani (Di ptera: Muscidae) and related species in Burkina Faso. Tropical Pest Management, 37: 231-235. Zongo, J.O., Vincent, C. and Stewart, R.K. 1992. Time-sequential sampl ing of the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), in Burkina Faso. Insect Science and its Application. (In press). •

• • 80

• TABLES AND FIGURE 1.

• • • •

Table 13. Yields and Land Equivalent Ratio (LER) for intercropped sorghum-cowpea in 1988 at Matourkou, 8urkina Faso.

Cropping Yields tlha LER LER LER System' Sorghum Cowpea Sorghum Cowpea Intercropping

S, 1.87 (0.76)' S, 1.14 (0.65) 0.60 (0.19)' 0.60 0.88 1.48 S, 0.83 (0.62) 0.59 (0.13) 0.44 0.86 1.30 S. 1.07 (0.87) 0.48 (0.19) 0.57 0.71 1.28 S, - 0.68 (0.11)

See Fig. 1 for plot design. Standard deviation based on four replicates.

81 • • •

Table 14. Yields and Land Equivalent Ratio (LER) for intercropped sorghum-cowpea in 1989 at 11atourkou, Burkina Faso.

Cropping Yields t/ha LER LER LER System' Sorghum Cowpea Sorghum Cowpea Intercropping

S, 1,47 (0,36)' S, 1,23 (0,86) 0,55{0,16)' 0,83 0,59 1,42 S, 0,96 (0,52) 0,54 (0,11) 0,65 0,58 1,23 S. 0,78 (0,53) 0,49 (0,11) 0,53 0,53 1,06 S, - 0,92 (0,21)

See Fig. 1 for plot design. Standard deviation based on four replicates.

82 if // li • il • • " \\ 1 ,i

Table 15. Average number of eggs laid, percentage of plants wlth eggs and percent age of de ad hearts due to A. soccat. In four cropplng systems ln Burkina faso.

1988 19B9 1991 Cropplng system 110. egg< ,; Plants' ,; Oead Hearts 110. eggs ,; Plants' ,; Oead Hearts 110. eggs ,; Plants' %Oead lIe.rts

1 b S, 4.46 • 4.46' 38.20' 5.75' 8.49' 30.3g 12.00' 27.43' 31. 95' S2 15.11' 8.40' 45.86' 6.75' 10.36' 19.71' Il.00' 25.74' 43.32' S3 9.37' 15.11' 47.36' 4.75' B.07' 24.6S'b 17.00' 32.27' 38.99' S, 8.40' 8.40' 29.48' 6.75' 11.11' 27.76'b 6.25' 23.36' 36.90'

%Plants bearlng eggs • Heans wlthln a column wlth the same letter are not signlfl~antly dlfferent P• 0.05, Scheffé's test.

83 • • •

1.'")

Table 16. Effect of sowing dates on yield and %dead hearts caused by the sorghum shoot fly Atherigona soccata in Matourkou, Burkina Faso, in 1988 and in 1989.

1988 1989 Sowing

Dates % Dead hearts Yield (t/ha) % Dead hearts Yield (t/ha)

June ZO 6.47"- Z.91" 10.20" 1.80Z" June 30 ZO.OI" Z.58" 13.68" 1.228b July 10 23.57" 1.59b 17 .61"b 1.004b

b bc July ZO 60.48 0.800< 30.13 0.491<

b d bc July 30 66.89 0.277 45.38 0.319<

- Means with the same letter are not significantly different, P = 0.05, Scheffés's test.

84 85 •

Figure 1. Spatial arrangement of sorghum and cowpea rows in five cropping systems. •

• •

en en en en en 0 U1 .... W N - en 0 I!f#$ fi*;9 '1 1..... cC ::r c= "' 3 N ep; eM e 4 i

Lji D 1(,)

li Il Il I~

:-' Il è ; Il len en 1 3 • li ;; • Il Il le> C'> 0 il lt> MN Il Ai 1'"-1 0>

Il 10)

1 lco

0 cr 1..... '"lt> 0 < !l!-a ::l ~ .. .. Gl en 3 • • 86

CONNECTING STATEMENT

In chapter 5, appropriate sorghum sowing dates have been proposed to avoid and reduce yield losses caused by the shoot fly. These sowing dates would be more effective if attention is paid to the choice of a suitable sorghum cultivar. In IPM, the choice of plant cultivar is important as growi ng pl ant cul tivars resistant to insects attack confers na~ural control. The use of resistant cultivars is one of the most desirable and compatible control method in IPM programs for many • agricultural insect pests (Kogan 1982). To choose an appropriate cultivar, effective screening techniques should be applied. Artificial and natural screening methods have been used to select sorghum cultivars resistant to the shoot fly (Singh and Rana 1986). In Chapter 6, l use natural methods to determine which local cultivars of sorghum are resistant to the shoot fly in Burkina Faso.

• • 87

6 Screening of Local Cultivars for Resistance to Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae), in Burkina Faso •

To be submitted to Sahel Phytoprotection, August 1992. Authors: ZONGO, J.O., VINCENT, C., STEWART, R.K . • 88 • 6.1. Abstract Experiments were conducted at Matourkou, Burkina Faso, using natural screening techniques to screen 52 local sorghum cultivars for resistance to sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae). The 52 local cultivars were compared to one resistant cultivar (15 2123) and one susceptible cultivar (C5H-l) introduced from India. Experiments were conducted in 19B8 and 1989 for 52 local cultivars and in 1990 and 1991 for eight local cultivars. Criteria used to assess the cultivars were the number of shoot fly eggs per 10 plants and the percentage of dead hearts per cultivar. Using t tests (Least 5ignificant Difference), significant differences were observed with respect to the number of eggs per 10 plants and to dead heart incidence. In all years, none of local cultivars received 'significantly fewer eggs and dead hearts than the resistant cultivar 15 2123. The • results indicated that damage to cultivars varied with the shoot fly population levels. Overall, none of the 52 Burkinabè sorghum cultivars was resistant ta shoot fly attack.

• 89 • 6.2. Introduction Sorghum, Sorghum bico7or (L. Moench), i s the most important cereal crop in Burkina Faso. Traditionally the crop is used as human food, beverages, animal feed and for fence construction. Among the factors reducing sorghum yields are insect pests, the important groups being those attacking stored grain, seedling foliage, and the head and stem of growing plants (Nwanze 1985). The shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), is one of the most important seedling pests in Burkina Faso (Bonzi 1981, Nwanze 1988). One of the strategies for reducing shoot fly damage is to use resi stant cul tivars. Sorghum cul tivars resi stant to shoot fly were first reported in India by Ponnaiya (1951), who screened 212 genotypes and found 15 to be less damaged. Taneja and Leuschner (1985) listed 42 cultivars as less susceptible over five seasons with five germplasm • lines which were quite stable at different locations. The main factors associ ated with shoot fly resi stance are physi co-morphol ogi cal (seedling vigor, glossiness, silica bodies, presence of hairs on the epidermi s) and bi ochemi cal factors (presence of compounds such as hordenine, alkaloid, dhurrin, cyanogenic glucoside, lysine, nitrogen and phosphorous content) (Singh and Rana 1986). The mechanisms of resistance found to interfere with the shoot fly are non-preference or antixenosis, antibiosis, and tolerance or recovery resistance (Singh. and Rana 1986). In Burkina Faso, Brenière (1972) screened eight and six cultivars at Sari a (Koudougou) and Boni respectively and foundsuscepti bi lity differences between cultivars. Local cultivars are adapted to each environmental site in Burkina • Faso as differences between rainfall are well pronounced. Therefore, 90 • the choice of a given cultivar should take into account these rainfall di fferences. The present study was carri ed out to screen 52 l ocal sorghum cultivars commonly used in the western region based on the number of eggs laid and the percentage dead hearts per cultivar. 6.3. Materials and Methods Experiments were conducted at Matourkou located about 10 km from Bobo-Dioulasso (11 0 Il'N, 40 18'W), Burkina Faso, West Africa. In 1988 and 1989, 52 local cultivars from the National Agricultural Research Institute (INERA), one resistant (IS 2123 from the USA) and one susceptible (CSH-l) cultivar from the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) India were used. In 1990 and 1991, eight local cultivars selected from 1988 and 1989 screening and the resistant cultivar IS 2123 were used. These • cultivars were retained because they received less than 50% dead hearts and fewer dead hearts than the susceptible CSH-l in 1988. The local cultivar "Gnofing" was used as a check. The experimental design was a randomized complete block with four repl icates. Each year, sowing was done on 20 July, one month after normal sowing dates to increase the l ikel ihood of high shoot fly infestation. Each cultivar was sown in a 4 m row. Row and intra-row spacings were 0.80 mand 0.10 mrespectively. One plant was maintained perhill. Natural screening techniques (Singh and Rana 1986) were used. The cultivar "Gnofing" was sown in two border rows between the blocks and on each side of each block to act as reservoir of shoot fly populations. These border rows were 1 m away from cultivars being • scre.ened. Row and intra-row spacings were 0.80 and 0.20 ni 91 • respectively. Two plants were maintained per hill in these border rows. The distance between blocks was 2.80 m. One week after border row plant emergence, 100 g/4 mrow of fish meal, purchased in a local market, was spread by hand to attract shoot flies. In 1990 and 1991, border rows were not used. One week after experimental cultivar emergence, 100 9 of fish meal was used per row for each cultivar. Fish meal was spread between 8.00 and 9.00 h adjacent to plants on both sides of each row. Thinning was done 15 days after sowing. Visual observations were made between 7.00 and 10.00 h, 13 and 28 days after plant emergence for egg and dead heart numbers respectively. Egg counting was do ne on ten randomly selected plants per row for each cultivar. Dead heart counting was done per row for each cultivar. The total numbers of plants, and plants bearing dead hearts were recorded. • Data were analyzed using t tests (LSD) of the software SAS (version 6.03 for the IBM PC) (SAS Institute Inc. 19BB). 6.4. Results Significant differences w~re observed with respect to the number of eggs per 10 plants and to dead heart incidence in all years (Ta~le 17, 18). In 1988, the mean number of eggs varied from 0.25 (IS 2123) to 7.75 (CVS 606) (Table 17). None of local cultivars received significantly fewer eggs than the susceptible CSH-l. Mean percentage of dead hearts ranged from 0.80% (IS 2123) to 78.8% (CVS.631) (Table 17). Ten local cultivars (CVS 578, CVS 586, CVS 606, CVS 611, CVS 617, CVS 628, CVS 633, CVS 638, CVS 643, CVS 644) showed significantly fewer dead hearts than CSH-l. None of the 54 cultivars was immune to shoot • fly attack. 92 • In 1989, shoot fly infestation was low. The mean number of e9gs and percentage of dead hearts ranged from zero (IS 2123) to 2.75 (CVS 600) and from 1.49 (IS 2123) to 27.49% (CVS 641) respectively. The cultivars IS 2123 and CVS 625 showed absol ute non-preference for oviposition by the shoot fly (Table 17). In 1990, the mean number of eggs per 10 plants varied from 0.00 (IS 2123) to 3.5 (Gnofing and CVS 586), whereas dead heart incidence ranged from 0.00 (IS 2123) to 33.59% (CVS 611) (Table 18). IS 2123 showed absolute resistance to the shoot fly. Although less shoot fly damage was recorded in 1991, egg numbers were higher th an in 1990. The mean number of eggs varied from 0.00 (IS 2123) to 14.67 (Gnofing) and percentage of dead hearts ranged from 0.20 (IS 2123) to 10.55% (CVS 643). 6.5. Discussion • Our results on shoot fly incidence indicated that damage to cultivars varied with years and degree of infestation. These findings have also been found by many authors i.e. Ponnaiya (1951), Singh et al. (1978), Sharma and Rana (1583), Taneja and Leuschner (1985), and Singh and Rana (1986). Highers number of eggs and percentage dead hearts were recorded in 1988 than in 1989. This may be due to more favorable climatic conditions for the shoot fly in 1988 (Zongo et al. 1991) None of the local cultivars was resistant to shoot fly attack. Brenière (1972), using six cultivars in 1964 in Boni (western part of Burkina Faso), also observed that hybrid cultivars (originating from crosses between American and Burkina Faso cultivars) were less susceptible to the shoot fly attack than their local parents although he concluded that this observation needs to be confirmed. Our results • strongly support his observation. 93 • Although no local sorghum cultivars showed resistance to shoot fly in Burkina Faso, resistant cultivars have been found from various countri es. Taneja and Leuschner (1985) listed 42 l ess susceptibl e sorghum cultivars among which 32 originated from 1ndia, 5 from Sudan, 3 from the USA, and one each from Ni geri a and South Afri ca, whereas Singh and Rana (1986) reported 73 resistant cultivars from various screening programmes. Singh and Rana (1986) mentioned that resistant sorghum cultivars found in various screening programmes are not generally good agronomic types because they are susceptible to lodging, photosensitive, late maturing, and low yielding. Singh et al. (1978) found that dead heart incidence in resistant cultivars changed over the seasons but never beyond 42.64% in 1ndia. Jotwani and Srivastava (1970) reported that under artificial screening conditions, some moderately resistant cultivars showed from 26.3% to 64.2% dead hearts, whereas • susceptible ones recorded up to 91.6% dead heart. Our results on local cultivars indicated a maximum percentage dead heart of 78.80% in 1988. The cultivar IS 2123, originating from the USA, showed high resistance and stability compared with the local cultivars. Taneja and Leuschner (1986) also found that IS 2123 showed moderate stability and has been used as a source of resistance in 1ndia. The resistance of IS 2123 tG shoot fly attack observed in our study was due to the non­ preference for oviposition, as less than 1.00 egg per ten plants were recorded during the four-year screening. This confirms Blum's (1967) and Jotwani et al. 's (1971) results that under field conditions, resistance -is primarily due to non-preference for oviposition. IS 2123 also showed antibiosis against the shoot fly (Singh and Narayana 1978). Although no resistant Burkinabè cultivars to shoot fly were found • in our study, screening of other local cultivars should be pursued. 94 • The cultivar 15 2123 might be a good source of resistance in developing local sorghum cultivars resistant to shoot fly. This suggests that a close liaison should be established between entomologist and breeder. The recommendation that may be made at the present time concerning the use of local cultivars is to practice early sowing dates, as Zongo et a7. (unpublished data) found that sowing sorghum at the beginning of the rainy season resulted in reduced shoot fly damage .

•

. ' 95 • 6.6. References Blum, A. 1967. Varietal resistance of sorghum to the sorghum shootfly (Atherigona varia var. soccata). Crop Sei. 7: 461-462. Bonzi, S.M. 1981. Fluctuations saisonnières des populations de la mouche des pousses de sorgho en Haute-Volta. Insect Sei. Applic. 2: 59-62. Brenière, J. 1972. Sorghum shoot fly in West Africa, pp. 129-135, In Control of sorghum shoot fly, (Jotwani, M.G. &W.L. Young Eds). Oxford and I.B.M., New Delhi. Jotwani, M.G., Sharma, G.C., Srivastava, B.G. and Marwaha, K.K. 1971. Oviposi tional response of shootfly. Atherigona varia soccata (Rondani) on sorne promising resistant lines of sorghum. In Pradhan, S. (ed.) Investigations on Insect Pests of Sorghum and Millets (1965-70), pp. 119-122. Final Technical Report, • Division of Entomology, IARI, New Delhi. Jotwani, M.G. and Srivastava, K.P. 1970. Studies on sorghum lines resistant against shootfly, Atherigona varia soccata (Rondani). Indian J. Entomol. 32: 1-3. Nwanze, K.F. 1985. Sorghum insect pests in West Africa, pp. 37-43, In International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). Proceedings of the International Sorghum Entomology Workshop, 15-21 July 1984. Texas A & M University, College Station, TX, USA. Patancheru, A.P. 502324 India: ICRISAT. Nwanze, K.F. 1988. Distribution and seasonal incidence of sorne major insect pests of sorghum in Burkina Faso. Insect Sei. Applic. 9: 313-321 . • 96 • Ponnaiya, B.W.X. 1951. Studies on the genus Sorghum 1. Field observations on sorghum resistance to the insect pest. Atherigona indiea M. Madras Univ. J. (B) 21: 96-117. SAS Institute Inc. 1988. SAS Language Guide for Personal Computers: Release 6.03 Edition. Cary, NC, USA. 558 pp. Sharma, G.C. and Rana, B.S. 1983. Resistance to the shoot fly, Atherigona soeeata (Rond.) and selection for antibiosis. J. Entomol. Res. 7: 133-138. Singh, R. and Narayana, K.L. 1978. Influence of different varieties of sorghum on the biology of the sorghum shootfly. Indian J. Agrie. Sei. 48: 8-12. Singh, B.U. and Rana, B.S. 1986. Resistance in sorghum to the shootfly, Atherigona soceata Rondani. Inseet Sei. App7ie. 5: 577-587 . Singh, S.P., Jotwani, M.G., Rana, B.S. and Rao, N.G.P. 1978. Stability • of host-plant resistance to sorghum shootfly, Atherigona soeeata (Rondani). Indian J. Entomo7. 40: 376-383. Taneja, S.L. and Leuschner, K. 1985. Resistance screening and mechanisms of resistance in sorghum to shoot fly, pp. 115-129. In International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). Proceedings of the International Sorghum Entomology Workshop, 15-21 July 1984. Texas A & M University, College Station, TX, USA. Patancheru, A.P. 502324 India: ICRISAT. Zongo, J.O., Vincent, C. and Stewart, R.K. 1991. Monitoring adult sorghum shoot fly Atherigona soeeata Rondani (Diptera: Muscidae), and related species in Burkina Faso. Trop. Pest Manag. 37: 231­ 235 •

. ' • 97

• 6.7. TABLES

• 98 Table 17. Mean number of shoot fly eggs/ 10 plants and me an percentage of dead hearts observed in 54 cultivars of sorghum at Matourkou, Burkina Faso .

Cultivar 1988 1989 • No. Eggs % dead hearts No. Eggs %dead hearts 15 2123 0.25 0.8 0 1.49 CVS-608 3.00 60.8 1.75 15.55 CVS-625 3.00 63.8 0 18.21 CVS-626 3.25 58.8 1.25 16.65 Frikan 3.25 60.3 0.5 20.89 CVS-574 3.50 57.8 2.25 23.57 CVS-587 3.50 60.5 1 16.18 CVS-624 3.50 66.0 1.25 22.88 CVS-631 3.50 78.8 0.5 25.39 CVS-578 3.75 50.3 0.25 16.99 CVS-619 3.75 64.5 1.5 12.97 CVS-634 3.75 71.5 1.25 19.56 CVS-635 3.75 71.5 1.75 14.40 CVS-639 3.75 60.3 0.75 18.56 CVS-641 3.75 67.3 0.75 27.49 Gnofing 3.75 58.8 0.5 21.48 CSH-l 4.00 70.5 1.25 17.63 CVS-586 4.00 48.8 0.75 5.68 CVS-600 4.00 61.0 2.75 22.08 CVS-601 4.00 68.5 0.75 20.15 CVS-610 4.00 73.0 0.25 17 .84 CVS-644 4.00 46.8 2.25 21.50 CVS-654 4.00 60.5 0.75 22.60 CVS-5BO 4.25 57.0 0.75 14.74 CVS-589 4.25 65.8 2 14.92 CVS-596 4.25 57.5 0.75 12.23 CVS-638 4.25 52.3 1.25 13.81 • CVS-652 4.25 62.0 0.75 22.B3 CVS-655 4.25 55.3 1.5 20.85 CVS-659 4.25 69.0 1.25 26.53 CVS-660 4.25 54.0 1.25 17.44 Ouédézouré 4.25 65.3 ·0.75 25.19 CVS-576 4.50 72.0 0.25 24.95 CVS-6Il 4.50 48.0 0.5 13.82 CVS-633 4.50 45.8 1.5 13.50 CVS-643 4.50 49.0 0.75 13.87 CVS-653 4.50 58.0 0.75 17 .81 CVS-602 4.75 60.5 0.5 12.99 CVS-620 4.75 56.3 1.25 9.31 CVS-646 4.75 54.8 2 18.09 CVS-617 5.00 47.0 2 11.90 CVS-582 5.25 55.5 0.5 17 .67 CVS-618 5.25 58.3 0.75 17.88 CVS-613 5.50 55.8 0.25 18.04 CVS-630 5.50 . 74.0 1 20.50 CVS-575 5.75 65.3 0.75 Il.51 CVS-584 5.75 60.3 1.75 21.49 CVS-623 5.75 64.3 0.75 15.31 CVS-594 6.00 66.0 1.25 9.36 CVS-614 6.25 64.5 1 14.82 CVS-593 6.50 53.5 1 11.15 CVS-629 6.50 57.3 1 16.88 CVS-628 7.00 48.3 0.75 19.4B CVS-606 7.75 52.0 1.25 20.34 LSO' 3.19 17.81 1.43 12.95 • Least Slgnlflcant Olfference at 5% level 99 •

Tabl e 18. Mean nurnber of eggs and rnean percentage of dead hearts observed in 9 cultivars of sorghurn, Matourkou, 1990, 1991.

Cultivar 1990 1991

No. Eggs %dead hearts No. Eggs %dead hearts

rs 2123 0.00 0.00 0.00 0.20 CVS6Il 2.75 33.59 5.33 4.28 CVS643 3.00 25.08 4.67 rO.55 CVS644 3.00 15.43 6.33 7.49 CVS628 3.25 24.35 8.00 4.02 CVS617 3.25 27.90 5.67 5.31 • CVS633 3.25 24.09 8.33 4.12 CVS586 3.50 24.99 3.00 2.45 Gnofing 3.50 25.04 14.67 5.51 LSD' 2.39 13.21 4.32 7.16

• Least Significant Difference at 5% level •

• 100 •

CONNECTING STATEMENT

Insect pest control has generally been obtained through the use of chemicals. As a result of the problems (e.g. toxicity to non target organisms, high prices, environmental contamination) associated with the use of syntheticinsecticides, l ocally obtainable products and socioeconomically sustainable plant protection tactics are being sought in developing countries. Among these is the use of natural pl ant extracts such as those from the neem tree Azadirachta indica A. Juss. (Meliaceae)". Neem pesticidal properties have been discussed at three international conferences held in Germany and Africa (Kenya) • (Schmutterer et a7. 1981, Schmutterer and Ascher 1984, 1987). In Burkina Faso, the tree grows well in any part of the country and is widely used for building materials (fence posts), and traditional medicine. Neem tree products could be an alternative insect control material for peasant farmers. Chapter 7 deals with the use of neem tree extracts as techni cally acceptabl e components of an IPM program to control the shoot fly.

• • 101

7 Effects of Neem Seed Kernel Extracts on Egg and Larval Survival of the Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae) . •

In press in Journal of Applied Entomology Authors: ZDNGO, J.O., VINCENT, C., STEWART, R.K• • 102 7.1. ABSTRACT • A two-year study was conducted to evaluate the effects of neem extracts on egg and larval mortality of the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae). Field experiments were conducted in 1990 and 1991 in a sorghum field at Matourkou (Burkina Faso, West Africa). The following treatments were applied: 1) carbofuran S G, 2) 20 kg/ha neem seeds/SOO L water, 3) 20 kg/ha neem seeds/SOO L water + 2. S L/ha adhesol, 4) 30 kg/ha neem seeds/SOO L water + 2.S L/ha adhesol, S) 2.S l/ha adhesol, 6) control (untreated plots). Significant differences among treatments were observed in the number of eggs laid, and the percentage of dead hearts. Significantly fewer eggs and dead hearts were observed in plots treated with neem extracts compared with adhesol and the control. In the laboratory, the treatments were: 1) commercial neem oil containing 0.63% azadirachtin, • 2) local neem oil, 3) 40 9 seed kernels/L water, 4) 40 9 seed kernels/L water + 5 ml adhesol, S) 60 9 seed kernels/L water + S ml adhesol, 6) S ml adhesol/L water, 7) control (untreated eggs). All neem seed extracts gave a significant lower percentage of egg hatching than the adhesol and control treatments. In larval survival experiments, commercial and local neem oil were not used. All treatments showed a significantly higher larval mortality compared with the controls.

•• 103 • 7.2. INTRODUCTION Sorghum, Sorghum bicolor (Linné, Moench), ranks first among the staple-crops in Burkina Faso. Its production is limited by a complex of insect pests among which the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), is an important one in the wetter southern zones (Nwanze, 1988). Shoot fly larvae feed on the central shoot of sorghum seedlings, causing a typical symptom called "dead heart". To control the shoot fly, systemic insecticides such as carbofuran are used to treat seeds (Mote, 1985). In practice however, the peasants of Burkina Faso do not have the capital and training to use chemical pesticides. Neem tree, Azadirachta indica A. Juss. (Meliaceae), products are known to have strong insecticidal properties (Schmutterer et al. 1981, Schmutterer and Ascher 1984, 1987, Jacobson, 1986) and could be • alternative pest control strategies for the farmers of Sahelian countries. The tree grows well in the Sahel and produces fruit, wood and leaves, all of which are used for a variety of purposes by peasant farmers. About 57 different chemical substances have been isolated from various parts of the neem tree (Jones et al. 1989). The most important active ingredient, azadirachtin (C"H"O.., see Jones et al. 1989), is mostly concentrated in the seeds (Saxena 1981, cited in Stoll 1986). In Burkina Faso, a survey done in 1986 and 1987 revealed that th~ leaves were traditionally used in warehouses to control stored grain pests (Zongo, unpubl ished data). Ahmed and Graigne (1985) reported that neem extracts can control up to 100 species of insects, mites and nematodes. Today, more than 200 insect species are reported to be control1ed by the pesticides derived from the neem tree (Hamilton, • 1992). Although neem products are effective against many insect 104 • species, few papers have been published on their effect on the sorghum shoot fly. Abdul Kareen et al. (1974) pointed out that neem kernel extracts caused 27% and 20% l ess shoot fly damage than an unsprayed control at a rate of 10 and 5 kg kernel s/ha (unknown azadi rachtin content) respectively. Chundurwar and Karanjkar (Parbhani) (19S0) concluded that neem oil decreased the percentage of plants bearing dead hearts compared with unsprayed plots (data not presented). No work has been yet published on the effects of neem extracts on egg and larval mortality of the sorghum shoot fly. This paper reports the results of a two-year study conducted in the laboratory and in the field on the effects of neem extracts on egg and larval mortality. 7.3. MATERIALS AND METHODS 7.3.1. Field experiments The experiments were conducted in 1990 and in 1991 at Matourkou, • located 10 km from Bobo-Dioulasso (11° lI'N, 4° lS'W), Burkina Faso. Each year, the local sorghum variety "Gnofing" was sown on 30 June in a randomized complete block design with four replicates. The seeds were treated with benomyl (Benlate 50% WP, Du Pont De Nemours, Switzerland) at a rate of 5 g/kg to prevent fungus attack. Each plot measured 3.20 x 4 m and contained four rows. Row and intra-row spacings were O.SO and 0.40 m respectively. Two seedlings were maintained per hill in all plots. The plots were fertilized with 200 kg/ha of NPK (15-15-15) applied on two occasions, 100 kg/ha at sowing_ time and 100 kg/ha 15 days after sowing. Fifty kg/ha of urea (46%) were applied 45 days after sowing. Neem seed kernels originated from Koudougou (12 0 43'N, 4°40'W), a city located in the central western part ,of Burkina Faso. In June and • JulY,1990, and in May and June 1991, fallen fruits were collected 105 • underneath neem trees. The flesh was removed from the seed and any remaining shreds were washed away with water. The seeds were then she11ed and dried one week in the sun. After drying, the good seed kernels were sorted and then stored at room temperature. In July of each year, a sample of dried seed kernels was shipped to Canada for azadi rachtin content analysi s. To assess azadi rachtin content, one 9 of ground seed kernels or seed oil was mixed with 10 ml of distilled water (i.e. 10% aqueous solutions). These were allowed to sit at room temperature for 24 h, then stored at S' C for a further 48 h before analysis. The azadirachtin content was determined using reverse phase gradient HPLC as described in Isman et al. (1990). Seeds were ground with a blender at high speed. The required adhesol quantity (5 ml/L water) was added to the seeds at grinding time. After grinding, 5 L of water was added to the ground seeds which • were then a11 owed to stand 24 h. The sol ution was then sieved and filtered through fine muslin. Six treatments were applied: 1) at sowing time, carbofuran 5 G (Procida/Roussel Uclaf, Abidjan, Côte d'Ivoire) was applied by hand at a rate of 1.5 g/m of row adjacent to the hills, 2) 20 kg/ha of neem seed kernels diluted in 500 L of water/ha, 3) 20 kg/ha of neem seed kernels in 500 L of water and mixed with 2.5 L/ha of adhesol EC (SOFACO/Roussel Uclaf, Abidjan, Côte d'Ivoire), 4) 30 kg/ha of neem seed kernels diluted with 500 L of water and mixed with 2.5 L/ha of adhesol EC, 5) adhesol EC, 2.5 L/ha diluted with 500 L/ha of water (adhesol is an emulsifiable concentrate containing condensate ethylene oxyde and non ionic terpene) and 6) the control plots (untreated). Neem seed kernel extracts were appl ied weekly starting after • plant emergence for five weeks. One hand operated sprayer was used per 106 • plot with the preloaded appropriate treatment of neem seed kernel extracts and adhesol. Spraying was done between 8.00 - 10.00 h on whole plants and individual leaves for 40 sec per plot (i.e. 10 sec per row). This procedure allowed about 16 ml of spray/second. Observations were made on eight occasions every fifth day, starting 10 days after sowing. Egg counting was done on the two central rows of each plot. The number of eggs and dead hearts was recorded and the number of plants per plot noted. On each samp li ng occasion, the plants showing dead heart symptoms were flagged with a piece of red cloth to avoid repeated counting. 7.3.2. Laboratoryexperiments In 1990 and in 1991, shoot fly eggs were collected between 8.00­ 10.00 h from untreated field plots sown at weekly intervals. The eggs were detached from the leaves using small scissors and were transferred • to Petri dishes containing wet filter paper. The eggs were examined under a bi nocul ar mi croscope and parasitized or damaged eggs were discarded. Eggs showing black-head formation before hatching were also discarded. Thirty eggs per treatment were used in a randomized compl ete bl ock desi gn repli cated four t imes. Seven treatments were applied: 1) control (untreated eggs), 2) commercial neem oil (Safer LTD, Victoria, B.C., Canada) containing 0.63% azadirachtin, 3) local neem oil, traditionally extracted by pressing seed kernels, 4) 40 9 seed kernels/L water, 5) 40 9 seed kernels/L water + 5 ml adhesol, 6) 60 9 seed kernels/L water + 5 ml adhesol, 7) 5 ml adhesol/L water. Five pl of each neem seed kernel extracts and adhesol were topically applied with a micro-pipette (Micromane Model M50). Five pl of 0.63% azadirachtin and local neem oil were spread on fil ter papers. A few • seconds later, the eggs were removed from the pieces of leaf and placed 107 • on the treated part of the filter paper. All eggs were then transferred into a rearing room at 26 Oc (± 1), 68-75% R.H., and a photoperiod of 12:12 (L/D). Observations were made daily on the number of eggs hatched until one week after treatments. To study the effects of neem extracts on larval survival, five first-instar larvae obtained from mass rearing were used per treatment in a randomized complete block design replicated four times. A. soccata adults were obtained from third instar larvae identified using Deeming's (1971), and Raina's (1981) description. Five treatments were applied including 1) control (treated with distilled water), 2) 40 9 seed kernels/L water, 3) 40 9 seed kernels/L water + 5 ml adhesol, 4) 60 9 seed kernels/L water + 5 ml adhesol, 5) 5 ml adhesol/L water. The analytical methods previously described were used to assess azadirachtin content. • About 500 ml of solution of each treatment was used in a small operated hand sprayer (8erthoud F2) that allowed a flow of 30 ml during 15 sec of spraying on five plants. Care was taken to ensure that the solution reached the central shoot of the plants. Fifteen minutes after treatment, a fine camel brush was used to transfer each larva into the central shoot of a 14 day-old plant from sowing, grown in a plastic pot. After transferring the larvae, each pot was put in a cage (40 x 40 x 40 cm) placed in an insectarium. One week after treatment, all plants were dissected to count living larvae. Data on the percentage of dead hearts and egg hatch ing was transformed to arcsin values. All data were analyzed using Scheffé's test of the software SuperANOVA (version 1.1 for the Macintosh • Computer) (Abacus Concepts Inc. 1989) . 108 • 7.4. RESULTS In 1990, seed kernels and seed oil contained 447 ppm and 93 ppm of azadirachtin in solution respectively, whereas in 1991 they yielded 508 ppm and 100 ppm respectively. 7.4.1. Field experiments In both 1990 and 1991, significant differences among treatments were observed in the number of eggs laid (F= 55.22, df= 5,15 p= 0.0001 in 1990 ; F= 31.06, df= 5, 15; p= 0.0001 in 1991) and the percentage of de ad hearts (F= 101.03, df= 5,15; p= 0.0001 in 1990; F= 74.96, df= 5,15; p= 0.0001 in 1991) (Table 19). In both 1990 and 1991, fewer eggs were laid in plots treated with neem extracts compared with carbofuran, adhesol and control plots. The average number of eggs and dead hearts (all data pooled per year) was higher in 1990 (31.91 eggs, 23.45% dead hearts) than in 1991 (17.66 eggs, 22.78% dead hearts) (Table 19) • In 1990, there were no significant differences between neem seed extracts (20 kg seed kernels/ha + 2.5 L adhesol/ha, 30 kg seed kernels/ha + 2.5 L adhesol/ha, and carbofuran in reducing dead heart formation. In 1991, the carbofuran treatment was significantly superior to all neem seed extracts in reducing dead heart formation. In 1990 and in 1991, all neem extracts gave a lower percentage of dead hearts than adhesol and controls. 7.4.2. Laboratory experiments Significant differences were obtained on the rate of hatching (F= 71.87; df= 6,18; p= 0.0001 in 1990; F= 60.48, df= 6,18, p= 0.0001 in 1991) (Table 20). All neem seed extracts gave a higher percentage of egg mortality than the adhesol and control treatments (Table 20). The treatment with adhesol had an egg mortality significantly higher than •• that observed in the control. There were no significant differences 109 between neem extracts and neem oil ( 0.63% azadirachtin, and local neem • oil) in causing egg mortal ity. Most of the unhatched eggs were compl etely decomposed 24 h after the treatment wi th neem aqueous extracts (Fig. 2) while they collapsed with neem oil . All treatments showed significantly higher larval mortality compared with the controls (F= 8.95, df= 4,12; p= 0.0007) (Table 21). 7.5. DISCUSSION The di fferent con centrations of azadi rachti n found in our samp les confirm Ermel et al. (1984) and Isman et al. (1990) results who found that azadirachtin content may vary according to the tree From which seeds were collected, the environmental conàitions, the year and the geographical area. In studying the azadirachtin content of 12 neem oil samples, Isman et al. (1990) reported a variation of azadirachtin From 50 to 4000 ppm with a subsequent variation in bioactivity From 72 to • 90%. The variations of the number of eggs laid, the percentage of egg hatching and dead hearts between 1990 and 1991 (Table 19, 20) could be due to the qualitative difference recorded in azadirachtin content. The neem seed extracts proved to be effective in reducing egg numbers in the field. This might be due to either an antiovipositional action or an ovicidal effect. The antiovipositional action of neem extracts has been observed on various insect pests by several authors including Das (1986), Hellpap and Mercado (1986), Bowry et al. (1986),. Rice et al. (1985), Saxena et al. (1981). For instance, AZT -VR-K, an enriched formulated neem seed kernel extract, gave 100% repellence at a concentration of 0.02% against the sheep blowfly, Lucilia sericata (Rice et al. 1985). Although little data are available on the ovicidal effect of neem • extracts, our results indicated a strong effect on the shoot Fly eggs. 110 • Mong and Sudderuddin (1978) found that high concentrations of ethanolic and aqueous neem extracts reduced the hatching rate of the diamondback moth, P7ute77a xy7oste77a L., eggs. Saxena et a7. (1981) obtained similar results by dipping the eggs of the rice leaffolder, Cnapha7ocrocis medina7is (Guenée), into neem oil at different concentrations (12, 25, 50%). But Schmutterer (1990) pointed out that these results were probab1y due to the choking effect of the neem oi1, as other vegetable oi1s (such as groundnut) will do, rather than the growth regu1ating properties of the neem ingredients. A partial suffocating effect cou1d have a1so occurred in our experiment as eggs were deposited on the filter paper parts treated with neem oil. Rovesti and Deseo (1991) reported inconsistent effects of neem extracts on egg morta1ity of the 1eafminer Leucoptera ma7ifo7ie77a Costa and suggested that this was probab1y due to qua1 itative differences • between the kerne1s stored for different times. The decomposition of eggs observed in laboratory conditions, mi9ht a1so have occurred in field conditions. But this wou1d not have happened without a uniform spraying of the neem extracts on the underside of the sorghum 1eaves where eggs are laid. Neem application shou1d be done in the morning after dew disappearance. Applications shou1d be done at least one hour after the rain. Schmutterer (1990) discussed the practica1 prob1ems of neem app1 ication and mentioned that the residua1 effect of neem products f~~g~ most1y from five to seven days. Consequently, he recommended that extensi on personnel exp1 ain we11 the de1ayed effect of neem products to farmers in order to avoid disapointments or premature wrong conclusions. The carbofuran treatment did not reduce egg 1aying. However, it . • a110wed plants to deve10p well and to escape from heavy shoot f1y III • damage. Sukhani and Jotwani (1982) found simil ar results and noted that the maximum number of eggs (31.75 eggs per 25 plants) were laid in plots treated with carbofuran (3G at a rate of 1.5 g/m row) compared with untreated checks (18.25 eggs per 25 plants). In the laboratory, adhesol caused 61.5% and 51.5% egg mortality in 1990 and in 1991 respectively. However, in field conditions, it neither prevented egg laying nor dead heart formation. In 1990 field experiments, it increased the potency of the solution in reducing dead heart formation when added to neem extracts. The reducti on of dead heart format ion here reported, confi rms Abdul-Kareem et a7. ' s (1974) results that were 27% and 20% of reduction of dead heart using 10 and 5 Kg kernels/ha respectively. Using neem oil at 0.6%, Chundurwar and Karanjkar (Parbhani) (1980) also noted a reduction in dead heart formation compared with the control. • Our results on the effect of neem extracts on the shoot fly l arvae suggested that there was an antifeedant effect. Raina (1981) suggested that the movement of the first-instar larvae to the base of the sorghum plant shoot could be due to a chemical attractant present in or around the growing point of the central shoot. The neem aqueo~s extracts and adhesol spread so that the solution could reach the sorghum central shoot, might alter this chemical attractant and cause a deterrent effect on shoot fly larvae. Many authors (e.g. Olâifa and Akingbohungbe 1987, Raffa 1987, Jacobson 1986, Saxena and Khan. 1986) have showed outstanding antifeedant properties of neem extract products against several pests. Gill and Lewis (1971) pointed out that an effective antifeedant.must be persistent, absorbed and translocated to the growing point of the treated plants. Otherwise selective attack by • insect pests will occur on the new growths of the plants while the 112 • older treated parts remain distasteful. More investigations are required in the case of the sorghum shoot fly larvae. In view of the low education level of Burkina Faso farmers and Sahelian farmers in general, their low agricultural income, the cost of pesticides and the local availability of the neem tree, neem products coul d be a techni cally acceptabl e component of an Integrated Pest Management approach to control the shoot fly.

•

• 113 • 7.6. REFERENCES Abacus Concepts Inc. 1989. SuperANOVA, Accessible General Linear Modeling, Berkeley, California, 316 p. Abdul Kareen, A., Sadakathulla, S., Venugopal, M.S. and Subramaniam, T.R. 1974. Efficacy of two organotin compounds and neem extracts against the sorghum shoot fly. Phytoparasitica 2, 127­ 129. Admed, S. and Grainge, M. 1985. The use of indigenous plant resources in rural development. Potential of the neem tree. International Journal for Development Technology 3, 123-130. Bowry, S.K., Pandey, N.D. and Tripathi, R.A. 1986. Evaluation of certain ail seed cake powder as grain protection against Sitophilus oryzae L. Indian J. Entomol. 46, 196-200 . Chundurwar, R.D. and Karanjkar (Parbhani), R.R. 1980. Control of • sorghum shootfly with neemoil and Decamethrin. Sorghum Newsletter 23, 82. Das, G.P. 1986. Effect of different concentrations of neemoil on the adult mortality and oviposition of Callosobruchus chinensis L. (Coleoptera: Bruchidae). Indian J. Agri. Sc. 56, 743-744. Deeming, J. C. 1971. Sorne species of Atherigona Rondani (Diptera: Muscidae) from Northern Nigeria, with special reference ta those injurious ta cereal crops. Bull. Entomol. Res. 61, 133-190. Ermel, K., Pahlich, E. and Schmutterer, H. 1984. Comparison of the azadirachtin content of neem seeds from ecotypes of Asian and African origin, pp. 91-93. In Schmutterer, H. and Ascher, K.R.S. eds. Proc. 2nd Int. Neem Conf. Rauischholzhausen 1983. Gill, J.S. and Lewis, C.T. 1971. Systemic action of an insect feeding • deterrent. Nature, 232, 402-403 114 • Hamilton, D.P. 1992. The wonders of the neem tree - Revealed! Science 255, 275. Hellpap, C. and Mercado, J.C. 1986. Effects of neem on the oviposition behaviour of the fall armyworm Spodoptera frugiperda Smith. J. Appl. Entomol. 105, 463-467. lsman, M.B., Koul, O., Luczynski, A. and Kaminski, J. 1990. lnsecticidal and antifeedant bioactivities of neem oil and their realationship to azadirachtin content. J. Agric. Food Chem. 38, 1406-1411. Jacobson, M. 1986. The neem tree: Natural resistance par excellence, pp. 220-232. In Green, M.B. and Hedin, P.A., eds. Natural resistance of plants to pests. Roles of allechemicals. American Chemical Society Symposium Series No. 296. Washington, D.C. 243 pp. • Jones, R.S., Ley, S.V., Morgan, LD. and Santafianos, 0.1989. The chemistry of the neem tree, pp. 19-45. In Jacobson, M. (ed.), 1988 Focus on Phytochemical Pesticides, Vol. 1, the Neem tree. CRC Press, Florida, USA. Mong, T.T. and Sudderuddin, K.I. 1978. Effects of a neem tree (Azadirachta indica) extract on diamondback moth (P7ute77a xy770ste77a L.). Mal. Appl. Biol. 7, 1-6. Mote, U.N. 1985. Efficacy of mixtures of carbofuran treated and untreated sorghum seed for the control of shootfly. J. Maharashtra agric. Univ. 10, 36-38. Nwanze, K.F. 1988. Distribution and seasonal incidence of some major insect pests of sorghum in Burkina Faso. lnsect Sei. Applic. 9, 313-321 . •• Olaifa, J.l. and Akingbohungbe, A.E. 1987. Antifeedant and 115 • insecticidal effects of extracts of Azadirachta indica, Petiveria a77iacea and Piper quineense on the variegated grasshopper, Zonocerus variegatus, pp. 405-418. In Schmutterer, H. and Ascher, K.R.S. eds. Proc. 3rd Int. Neem Conf. Nairobi, Kenya 1986. Raffa, K.F. 1987. Influence of host plant on deterrence by azadirachtin of feeding by fa" armyworm larvae (Lepidoptera: Noctuidae). J. Econ. Entomol. 80, 384-387. Raina, A.K. 1981. Movement, feeding behaviour and growth of larvae of the sorghum shoot fly Atherigona soccata. Insect Sci. Applic. 2, 71-81 Rice, M., Sexton, S. and Esmail, A.M. 1985. Antifeedant phytochemical blocks oviposition by sheep blowfly. J. Aust. Entomol. Soc. 24, 16. • Rovesti, L., and Deseo, K.V. 1991. Effectiveness of neem seed kernel extract against Leucoptera ma7ifo7ie77a Costa (Lep., Lysnetiidae). J. Appl. Entomol. Ill, 231-236. Saxena, R.C. 1981. Neem seed ail for leaf folder control. Plant Prat. News (Philippines) 10, 48-50 Saxena, R.C., Waldbauer, G.P., Liquida, N.J. and Puma, B.C .. 1981. Effects of neem seed ail on the rice leaffolder Cnapha7ocrocis medina7is, pp. 189-204. In Schmutterer, H., Aschter, K.R.S. and Rembold, H. (eds.). Natural pesticides from the neem tree Azadirachta indica A. Juss. Proc. lst Int. Neem Conf. Rottachegrern, 16-18, June 1980. GTZ 6236 Eschborn 1. 297 pp. Saxena, R.C. and Khan, Z.R. 1986. Aberrations caused by neem ail odour in green leafhopper feeding on rice plants. Entomol. Exp . • Appl. 42, 279-284. 116 • Schmutterer, H. 1990. Properties and potential of natural pesticides from the neem tree, Azadirachta indica. Annu. Rev. Entomol. 35, 271-297. Schmutterer, H. and Ascher, K.R.S. 1984. Natural pesticides from the neem trees Azadirachta indica A. Juss, and other tropical plants. Proc. 2nd Int. Neem Conf. Rauischholzhausen, 25-28 May, 1983. GTZ, Eschborn 1., 587 pp. ______. 1987. Natural pesticides from the neem tree Azadirachta indica A. Juss, and other tropical plants. Proc. 3rd Int. Neem Conf. Nairobi, Kenya 10-15 July, 1986. GTZ, Eschborn 1. 703 pp. Schmutterer, H., Aschter, K.R.S. and Rembold, H. 1981. Natural pesticides from the neem tree Azadirachta indica A. Juss. Proc. Ist Int. Neem Conf. Rottachegrern, 16-18, June 1980. GTZ, Eschborn 1., 297 pp. • Stoll, G. 1986. Natural crop protection, based on local resources in the tropics and subtropics. Josef Margraf, Publisher. Aichtal, Federal Republic of Germany. 186 pp. Sukhani, T.R. and Jotwani, M.G. 1982. Spot treatment of granular insecticides for the control of sorghum shootfly, Atherigona soccata Rondani. Indian. J. Entomol. 44, 117-120 .

• • 117

• 7.7. TABLES AND FIGURE 2•

• • 118

• • 119

Table 20. Effect of neem seed kernel extracts on the eg9 mortality of A. soccata in laboratory conditions, Burkina Faso.

%Mortality (n- 30) Treatment 1990 1991

Neem oil 0.63% azadirachtin 87.5a" 88.3a 40 9 of seed kernel/ 87.5a 91.7a L water + adhesol 60 9 of seed kernel/ 85.0a 90.8a L water + adhesol • Local neem oil 83.3a 88.3a 40 9 of seed kernel/ 81. Sa 85.84a L water 5 ml of adhesol/ 61.5b 51.5b L water Control 29.0c 23.4c

" Means within a column with the same letter are not significantly different, P • 0.05, Scheffé's test.

• • 120

Table 21. Effect of aqueous neem seed kernel extracts on larval mortality of A. soccata in 1991, Burkina Faso.

Treatment % Mortality of larvae

40 9 of seed kernel/l 55.0b" water + adhesol 60 9 of seed kernel/l 55.0b water + adhesol 40 9 of seed kernel/l 50.0b water Adhesol 50.0b • 5 mll l water Control O.Oa (Distilled water)

• Mean percentages with the same letter are not significantly different, P• 0.05, Scheffé's test•

. ' 121 •

Figure 2. Shoot fly eggs decomposed 24 h after treatment with neem • aqueous extracts.

• •

•

• • 122

CONNECTING STATEMENT

In the previous chapters, l investigated five shoot fly control tactics including monitoring, time-sequential sampling, cultural practices, host plant resistance, and the use of a biopesticide from the neem tree. An IPM program requires the use of several combined tactics that will signi fi cantly reduce pest damage wi thout harmful impact on the environment. The use of natural enemies against a given insect pest should be considered as an important component in IPM • programs (Surn et al. 1987). This tactic, known as biological control, is a harmless component to human beings and the environment. It implies research on which natural enemies will provide control, and how to conserve or augment the number of these natural enemies. In chapters 8 and 9, l will investigate the impact of cultural activies using intercropping of sorghum and cowpea on biocontrol agents. The main goal is to identify candidate species which are likely to enhance shoot fly suppression .

• • 123

8 Effects of Intercropping Sorghum-Cowpea on Natural Enemies of the Sorghum Shoot FlY, Atherigona soccata Rondani (Diptera: Huscidae). in • Burkina Faso

In press in Biological Agriculture &Horticulture Authors: ZONGO, J.O" VINCENT, C. STEWART, R.K. • 124 • 8.1. ABSTRACT Experiments were conducted in 1990 and 1991 at Matourkou near Bobo-Di oul asso, Burki na Faso (West Afri ca), to study the effect of intercroppin9 sor9hum-cowpea, Sorghum bico7or L. (Moench)- Vigna ingucu7ata (Walp.), on the natural enemies of the sor9hum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae). Sampl ing was done weekly, on six occasions starting 10 days after sowing. Natural enemies of eggs were Trichogrammatoidea simmondsi Nagaraja (Hymenoptera: Trichogrammatidae), Tapinoma sp. (Hymenoptera: Formicidae), Fusarium sp. and a bacterium, Corynebacterium sp. Other insect species included a thysanopteran (Phlaeothripidae, Haplothripinae) and Dicrodiphosis sp. (Diptera: Cecidomyiidae) which were also associated with the sorghum shoot fly eggs. No significant differences were observed between the pure sorghum and the intercropped sorghum-cowpea with rl~spect to T. • simmondsi parasitism. Larval parasitoids were Neotrichoporoides nyemitawus Rohwer (Hymenoptera: Eulophidae), (6 to 17.50% of parasitism), Bracon sp. (Hymenoptera: Braconidae), and Hockeria sp. (Hymenoptera: Chalcididae). One pupal parasitoid was recorded, A7ysia sp. (Hymenoptera: Braconidae). Significant differences were observed in the percentage of larval parasitism in 1990 and in 1991 betwee: the pure sorghum and intercropped sorghum-cowpea. There was about two-fold and 1.4-fold increased larval parasitism in intercropped sorghum-cowpea in 1990 and 1991 respectively. Morisita's index of similarity (0.94. in 1990, 0.98 in 1991) between pure sorghum and intercropped sorghum·~ cowpea (0.9B between 1990 and 1991), indicated that the parasitoid species composition was independent of both the cropping system and the • year. 125 • 8.2. INTRODUCTION Intercropping has been defined as growing two or more crops simultaneously in the same field (Vandermeer 1989). This practice may increase (Risch et al. 1983, Vandermeer 1989) or decrease (Pimentel 1961, Risch et al. 1983) the abundance of natural enemies of a given pest. Intercropping sorghum-cowpea is a common practice in Burkina Faso, the former crop being attacked by the shoot fly, Atherigona soccata Rondani (Diptera: Muscidae). A. soccata has a wide range of natural enemies including egg parasitoids (Pont 1972, Taley and Thakare 1979, Deeming 1971, Delobel 1983, Delobel and Lubega 1984), larval parasitoids (Kundu and Kishore 1972, Pont 1972, Taley and Thakare 1979, Del obel 1983), pupal parasitoids (Deeming 1971, Taley and Thakare 1979), spiders and birds (Del obel and Lubega 1984). Deeming (1983) found that the most common • prey of the wasp Dasyproctus bipunctatus Lepeletier and Brullé (Sphecidae), are adult Atherigona spp. Delobel and Lubega (1984) stated that unidentified species of spiders and birds are important natural enemies of the sorghum shoot fly. Young (1981) noted that research on biological control of the shoot fly has been neglected. No work has been published so far on the effect of intercropping on the natural enemies of the sorghum shoot fly. The hypothesis examined here was that the population density of egg, larval and pupal parasitoids would be less abundant in a monoculture than in an intercropped system. We al so recorded other potential biocontrol agents of the shoot fly. 8.3. MATERIAL5 AND METHOD5 The study was carried out in 1990 and 1991 at Matourkou, located • approximately 10 km from Bobo-Dioulasso (11 0 Il', 40 18'W), Burkina 126 • Faso, West Africa. Each year, the local sorghum cultivar "Gnofing" and the cowpea cultivar TVx 3236 were sown on 15 July in a randomized complete block design with four replicates. Each plot measured 13.5 x 9 m and contained 18 rows. Three cropping systems were established: pure sorghum, 50% sorghum/50% cowpea sown in alternate rows, and pure cowpea. Row spacings were 0.75 m in all plots and intra-row spacings were 0.25 and 0.20 mfor sorghum and cowpea respectively. One and two seedlings were maintained per hill for cowpea and sorghum respectively. Plots were fertilized with 200 kg/ha of NPK (15 15 15) applied on two occasions: 100 kg/ha at sowing, and 100 kg/ha 30 days after sowing. Fifty kg/ha of urea (46% N) were applied 45 days after sowing. No pesticides were applied during the study. Sampling was done weekly, on six occasions starting 10 days after sowing . 8.3.1. Egg parasitoid sampling • In each plot, five rows of sorghum were randomly selected. Twenty shoot fly eggs were collected between 8.00 and 10.00 h from randomly selected plants within these rows. ·Pieces of sorghum leaves with eggs were removed using small scissors. The eggs were then transferred to Petri dishes containing wet filter paper and brought to the laboratory. They were examined with a binocular microscope and damaged eggs were discarded. Undamaged eggs were placed on filter paper (10 x 80 mm) and transferred to small vials (25 x 95 mm). The vials were closed with a wet cotton plug and kept under observation for two weeks in a rearing room set at 26 (± 1) ·C, 75% R.H.(± 2) and 12:12 (L/D) photoperiod. To feed emerging adults, a diet comprising 1/3 honey and 2/3 distilled water v/v was streaked inside the vial using a fine camel .' brush. Observations were recorded daily, and emerging adult parasitoids 127 • were counted and removed from the vials. Fourteen days after field collection, all remaining eggs were dissected in Ringer's solution using two fine pins to detect the presence of unemerged parasitoids. 8.3.2. Larval and pupal parasitoid samplinq Twenty pl ants showing dead hearts were randomly sel ected and removed from each plot. In the laboratory, these plants were dissected. The larvae were removed and transferred individually to plastic cups (30 ml; from Priee Daxxion, Saint-Laurent, Québec, Canada). Four holes (2 dia. mm) were eut in the lids. Each larva was provided with 1 9 of artificial diet (Singh et a7. 1983), which was repl aced every second day. Pupae were transferred i ndi vidually to similar plastic cups containing sterilized sand (6 g), which was wetted every second day with 10 droplets of distilled water. Parasitoid emergence was recorded daily. Emerged shoot fl ies were kept in 70% • alcohol for identification. 8.3.3. Funqi and bacteria samplinq All dark eggs collected from the field were retained. These eggs were disinfected by dipping them in 1% sodium hypochlorite (NaOC1) for one minute and then rinsing them with distilled water. Isolation was done on Potato Dextrose Agar (PDA), (DIFCO Inc.) medium. The microorganisms were then subcultured in legume juice (V8 medium, 200 ml legume juice,

3 9 MgC03 , 15 9 Agar). Insect species were identified by the International Institute of Entomology, London, U.K •. Voucher specimens were deposited in the Lyman Museum, Macdonald Campus of McGill University, Sainte-Anne'de Bellevue, Québec, and at the Biosystematic Research Center, Ottawa, Canada. Fungi were identified by USDA Plant Protection Research, US • Plant, Soil &Nutrition Lab., Ithaca, New York, USA. The fungi here 128 • isolated has been deposited into the USDA-ARS Collection of Entomopathogenic Fungal Cultures (ARSEF), Boyce Thompson Institute, Ithaca, New York, USA (Humber, person al ccmmunicat~~n). Bacteria were identified by MDS Laboratories, Montréal, Québec, Canada. Data on percentage of parasitism was analyzed using ANOVA followed by Scheffé's test of the software SuperANOVA (version 1.1 for the Macintosh Computer) (Abacus Concepts Inc., 1989). Morisita's index of similarity (MI) (Morisita 1959) was used to compare species composition between the two crops, and among the two years. The x2 (chi­ square) test (Steel and Torrie, 1980) was used to compare total number of egg, larval and pu pal parasitoid individuals between the two crops. 8.4. RESULTS 8.4.1. Shoot fly complex Species of shoot fly collected from sorghum shoots included A. • soccata, Sco7iophtha7mus micantipennis Duba (Diptera: Chloropidae), Si7ba pectita J.F. McAlpine (Diptera: Chloropidae) and Diopsis apica7is Dalman (Diptera: Diopsidae) (Table 22). All specimens of the genus Atherigona, were A. soccata. A. soccata were significantly (P = 0.05) more abundant in pure sorghum than in intercropped sorghum-cowpea (Table 22). Larvae of Sco7iophtha7mus micantipennis were commonly associated (6 to 9 larvae per sorghum shoot) with the A. soccata larva. The former were usually smaller in size than the A. soccata larvae and were found in the upper part of the damaged shoots. They were most frequent when the damage on the central shoot was well developed. 8.4.2. Egg natural enemies In both 1990 and 1991, shoot fly eggs were commonly parasitized by Trichogrammatoidea simmondsi Nagaraja .. Parasitism was recorded from • 17 to 38 days after sowing in both cropping systems. Based on pooled 129 • data each year, rate of parasitism was highest 24 days after sowing in both cropping systems (Fig. 3). Although the highest rate of egg parasitism was recorded in intercropped sorghum-cowpea (8.75% in 1990; 12.3% in 1991), no significant differences were observed between the levels in pure sorghum and the intercropped sorghum-cowpea (Table 23). The male:female sex ratio of T. simmondsi was 1:1.28 and 1:1.37 in 1990 and 1991, respectively. Among the 305 A. soccata eggs examined, the numbers of T. simmondsi exit holes per egg were: one (44.92%), two (53.45%) and three (1.63%). In the course of laboratory experiments, Tapinoma sp. Forster (Hymenoptera: Formicidae) was found preying on shoot fly eggs. One individual was found to destroy up to 18 eggs per day. Mites such as Suidasia pontifica Oudemans (Astigmata: Saproglyphidae) and sorne species of the family Histiotomatidae, were • found in association with shoot fly eggs in great numbers (7 to 13 per sampling date). A fungus, Fusarium sp. Link ex Fr., and a bacterium, Corynebacterium sp. Lehmann and Neuman, were isolated from shoot fly eggs. Technically it was difficult to quantify parasitism by these microorganisms owing to lack of facilities. A thysanopteran (Phlaeothripidae, Haplothripinae) and Dicrodiphosis sp. (Diptera: Cecidomyiidae) were also found associated with eggs. 8.4.3. larval and pupal parasitoids Neotrichoporoides nyemitawus Rohwer (Hymenoptera: Eulophidae) was the most, important endo-larval parasitoid. Significant differences

were found on the percentage of larval parasitism in 1990 (F = 66, df • = 1,3, P < 0.0001) and in 1991 (F = 30, df = 1,3, P = 0.0015) between 130 • the pure sorghum and intercropped sorghum-cowpea (Table 23). There was about two-fold and 1.4-fold increase in larval parasitism in intercropped sorghum-cowpea in 1990 and 1991 respectively. The highest percentage of larval parasitism was II.75 and 17.50% in 1990 and 1991 respectively. Parasitism was detected from 17 to 45 days after sowing. In 1990, using pooled data, percentage larval parasitism was found to be highest 31 days after sowing in both cropping systems (Fig. 3). In 1991, percentages of parasitism were highest 31 and 38 days after sowing in pure sorghum and intercropped sorghum-cowpea respectively (Fig. 3). The larval parasitoids Bracon sp. (Hymenoptera: Braconidae) and Hockeria sp. (Hymenoptera: Chalcididae) were also found emerging from field collected shoot fly larvae. One pupal parasitoid, A7ysia sp. (Hymenoptera: Braconidae), was recorded . Total number of shoot fly parasitoid species collected in 1990 • and 1991 is given in Table 24. All shoot fly parasitoids were present in both years and both cropping systems. Morisita's index of similarity (MI) between pure sorghum and intercropped sorghum-cowpea was 0.94 and 0.98 in 1990 and 1991 respectively. Using pooled data, MI was found to be 0.98 between 1990 and 1991. 8.5. DISCUSSION In both years, A. soccata was the species of the genus Atherigona attacking sorghum. This confirms the results of Nwanze (1988) who found up to 96% of A. soccata in sorghum shoots collected both from farmers and research station fields. A. soccata larva was found in the same sorghum shoot with larvae of the species Sco7iophtha7mus micantipennis and Si7ba pectita. We did not find solitary larvae of these species in the sorghum shoots. However, Deeming (1971) recorded • sol itary l arvae of S. micantipennis destroyi ng young sorghum seedl ings. 131 • Our observations confirm his more common finding that of about a dozen S. micantipennis larvae associated with A. soccata larva in the same shoot. Damage by A. soccata may make sorghum shoots more attractive to S. micantipennis, which may be considered as an opportunistic pest. Although sorne species of Diopsis attack undamaged rice plants, those which attack other grasses, such as Diopsis apica7is, are known to only attack already damaged plant tissues (I.M. White, personal communication). Trichogrammatoidea simmondsi Nagaraja was an important shoot fly egg parasitoid. This is a first record on A. soccata eggs. Trichogrammatoidea spp. are mainly egg-parasites of Lepidcptera, and to . a lesser extent, of few other insect orders (Nagaraja;. 1978). T. simmondsi has been recorded on rice· pests, such as Chi70 sp. (Pyralidae), Chi70 parte77us Swinhoe (Lepidoptera: Pyralidae), Sepedon • angu7aris (Diptera: Sciomyzidae), and Diopsis thoracica Westwood (Diopsidae) (Na9araja, 1978). Feijen and Schulten (1981) recorded T. simmondsi on the rice stalk-eyed fly Diopsis macrçphtha7ma Dalm (= thoracica Westwood) in Malawi and concluded that its importance as a parasitoid was secondary or marginal. Another species, Trichogrammoidea bactrae Nagaraja, has been recorded on A. soccata eggs in India (Rao et a7. 1987). Other species of the genus Trichogramma are also egg parasitoids of the shoot fly. Deeming (1971) recorded Trichogramma evanescens Westwood in Nigeria, whereas Taley and Thakare (1979) reported T. austra7icum Girault (= chi70nis Ishii) in India. Delobel (1983) recorded T. ka7kae in Kenya. So far, two species (Trichogrammatoidea bactrae and T. simmondsi) of the genus Trichogrammatoidea and three speci es (Tri chogramma • evanescens, T. ka7kae and T. austra7icum) of the genus Trichogramma are 132 • known to be egg parasitoids of the sorghum shoot fly. Our results on the number of exit holes of T. simmondsi indicate that one (44.92%) or two (53.45%) individuals emerged per ho st egg. Nagaraja (1978) found an average of 2 and 2.1 exit holes on O. macrophtha 7ma eggs in fi eld and l aboratory respect ively. Superparasitism occurred as there were 1.63% eggs with three exit holes per egg. Tapinoma sp. was a voraci ous egg predator in the 1aboratory. Many speci es of the genus Tapinoma are opportuni stic nesters often found in tufts of dead grass, plant stems, urban environments and other local sites (Hôlldobler and Wilson, 1990). Forel (1920) mentioned that Tapinoma is a large widely distributed and common genus. This suggests that the Tapinoma sp. here recorded may be a potential shoot fly egg predator to look for. Tapinoma sp. constitutes a first record on A. • soccata eggs. Suidisia pontifica individuals were associated in great number (from 7 to 13 per sampling date) with sorghum shoot fly eggs. These mites are mycophagous and show various degrees of selectivity in choosing fungi (Sinha, 1966). Our observations were not conclusive in fi ndi ng mites as predators of shoot fly eggs. However, Reddy and Davies (1978) found a predacious mite, Abro7ophus sp. (Acari: Erythraeidae) feeding on A. soccata eggs in India. The genus Fusarium has a wide range of insect hosts. Species such as F. avenaceum (Fries) Saccardo, and F. merismoides Corola, are found on Lymantria dispar L. (Lepidoptera: Lymantriidae) egg mass (Humber and Soper 1986). Corynebacterium sp. is a bacterium widely distributed in nature •• in the animal kingdom, sorne species being found in birds and insects 133 (Buchanan and Gibbons, 1974). • So far, no microbial control agent has been found on shoot fly e9gs. Therefore, Fusarium sp. and Corynebacterium sp. are the first 'record on the sorghum shoot fly e99s. They could be potential microbial control agents. Other suspected predators such as Dicrodiphosis sp. and Haplothipinae (Thysanoptera: Phlaeothripidae) were associated with shoot fly eggs. Larvae of Dicrodiplosis species are usually predators on mealy bugs (K.M. Harris, personal communication). More investigation are needed to confirm the real status of these insects on the sorghum shoot fly eggs. The most important endo-larval parasitoid was N. nyemitawus. In our study, the percentage parasitization ranged from 6.00 to 17.50%. Taley and Thakare (1979) recorded 1.59 to 8.33% parasitism due to N. • nyemitawus, whereas Rawat and Sahul (1968) reported 22 to 30% in India. Our highest numbers (11.75 in 1990, 17.50% in 1991) of parasitized shoot fly l arvae was recorded in intercropped sorghum-cowpea. This shows that intercroppi ng sorghum-cowpea had a benefi ci al effect in increasing N. nyemitawus populations. Bracon sp. and Hockeri a sp. were present in sma11 numbers'. They constitute a first record on A. soccata larvae. Hockeria Walker is a worldwide genus and contains about thirty described species (Halstead,. 1990). Although other larval-pupal parasitoids such as Spalangia endius Wal ker, Trichopria sp., Opius sp., and pupal parasitoids such as Monelata sp., and Rhoptromeris sp. have been recorded in India (Taley and Thakara, 1979), Alysia sp. was the only pupal parasitoid in our • study. Deeming (1971) also recorded Alysia sp. in Nigeria. 134 • No parasitism due to T. simmondsi and N. nyemitawus occured on the 10 th day after sowing. This was due to the lack of shoot fly eggs and larvae at that period. In 1988 and 1989, longo et al. (1992) also recorded no shoot fly eggs ten days after sowing at Matourkou. The most susceptible stage of sorghum for shoot fly attack is within 21 days after germination (Jotwani et al., 1970). The fluctuation of parasitism suggests that T. simmondsi could reduce shoot fly populations better than N. nyemitawus within the susceptible stage of sorghum. Our results on the shoot fly parasitoid species composition indicated that there was a high similarity between the two cropping systems and between the years. High Morisita similarity index values (0.94 in 1990 and 0.98 in 1991 between pure sorghum and intercropped sorghum-cowpea, 0.98 between 1990 and 1991) here reported indicated • that the parasitoid species composition was independent of the cropping system and of the year. Although the intercropped sorghum-cowpea did not show significant differences compared with pure sorghum with respect to egg parasitism, it could increase N. nyemitawus populations and also give ;: good combined yield of sorghum and cowpea as longo et al. (unpubl ished data) found an agronomie advantage of practicing this cropping system. longo et al. (1992) recommended that control measures be taken against the shoot fly before dead heart formation. Further to this recommendation, egg natural enemies such as Trichogrammatoidea simmondsi, T. bactrae, Trichogramma spp., Tapinoma sp., Abrolophus sp., Fusarium sp., Corynebacterium sp., may be the appropriate biological or microbial control agents to look for inimplementing any biological • control strategy. 135 • 8.6. REFERENCES Abacus Concepts Inc. (1989) SuperANOVA, accessib7e genera7 7inear mode7ing, Berkeley, CA., 316 p. Buchanan, R.E. &Gibbons, N.E. (1974) Bergey's manua7 of determinative bacterio7ogy, pp. 599-617. The Williams & Wilkins Company Baltimore. Deeming, J. C. (1971) Sorne species of Atherigona Rondani (Diptera: Muscidae) from Northern Nigeria, with special reference to those injurious to cereal crops. Bu77etin of Entomo7ogica7 Research, 61, 133-190. (1983) Atherigona spp. (Dipt., Muscidae) as prey of Dasyproctus bipunctatus Lepeletier and Brullé (Hum., Sphecidae) in Uganda. Entomo7ogist's Month7y Magazine. 119, 83 . Delobel, A. (1983) Etude des facteurs déterminant l'abondance des • populations de la mouche du sor9ho, Atherigona soccata Rondani (Diptères, Muscidae). Thèse de Doctorat d'Etat, Université de Paris Sud, Centre d'Orsay. ORSTOM, Paris. 127 pp. Delobel, A.G.L., &Lubega, M.C. (1984) Rainfall as a mortality factor in the sorghum shootfly, Atherigona soccata Rond. (Dipte!"a, Muscidae). Zeitschrift Fûr Angewandte Entomo7ogie (Journa7 of App7ied Entomology) 97, 510-516. Feijen, H.R., &Schulten, G.G.M. (1981) Egg parasitoids (Hymenoptera; Trichogrammatidae) of Dicpsis macrophtha7ma (Diptera; Diopsidae) in Malawi. Nether7ands Journal of Zoo7ogy, 31, 381-417. Forel, A. (1920) Les fourmis de 7a Suisse, La Chaux-de-Fonds, Imprimerie Coopérative, 333 p. Halstead, J.A. (1990) Revision of Hockeria Walker in the nearctic • region with descriptions of males and five new species 136 • (Hymenoptera: Chalcididae). Proceedings of the Entomo7ogica7 Society of Washington, 92, 619-640. Hëlldobler, B. &Wilson, E.O. (1990) The ants, The Belknap Press of Harvard University Press, Cambridge, Massachusetts, 732 p. Humber, R.A., & Soper, R.S. (1986) USDA-ARS Co77ection of entomopathogenic funga7 cu7tures, Catalog of Strains USDA-ARS Plant Protection Research Unit Boyce Thompson Inst., Cornell Univ. New York, pp. 25. Jotwani, M.G., Marwaha, K.K., Srivrstava, K.M., &Young, W.R. (1970) Se as on al incidence of shootfly (Atherigona varia soccata Rond.) in jowar hybrids at Delhi. Indian Journa7 of Entomo7ogy, 32, 7­ 15. Kundu, G.G:, &Kishore, P. (1972) New record of parasites of Sesamia inferens (Walker) and Atherigona nudiseta Rondani infesting minor • millets. Indian Journa7 of Entomo7ogy, 33, 466-467. Morisita, M. (1959) Measuring of interspecific association and similarity between communities. Memoirs of the Facu7ty of Science, Kyushu University. Ser. E (Bio7.) 3, 65-80 Nagaraja, H. (1978) Studies on Trichogrammatoidea (Hymenoptera: Trichogrammatidae). Orienta7 Insects 12, 489-350. Nwanze, K.F. (1988) Distribution and seasonal incidence of sorne major insect pests of sorghum in Burkina Faso. Insect Science and its App7ication, 9, 313-321. Pimentel, D. (1961) The influence of plant special patterns on insect populations. Anna7s of Entomo7ogica7 Society of America, 54, 61­ 69. Pont, A.C. (1972) The oriental species of Atherigona Rondani. In • Contro7 of sorghum shoot f7y, (Jotwani, M.G. &Young, W.R. eds.), 137 • pp. 27-104. Oxford &IBH, New Delhi. Rao, K.J., Thontadarya, 1.S. & Suhas, Y. (1987) Trichogrammatoidea bactrae Najaraja -A new egg parasitoid of sorghum shoot fly Atherigona soccata Rondani. Current Science 56, 283. Rawat, R.R. & Sahul, H.R. (1968) New record of Tetrastichus nyemitawus Rohwer (Hymenoptera: Eulophidae) as a parasite of Atherigona sp., the wheat stem fly in Madhya Pradesh. Indian Journa7 of Entomo7ogy, 3D, 319. Reddy, K.V.S. &Davies, J.C. (1978) A predacious mite on the eggs of sorghum shoot fly Atherigona soccata (Diptera: Muscidae) at Hyderabad. Acara70gy News7etter 6, 9. Risch, S.J., Andow, D. & Altieri, M.A. (1983) Agroecosystem diversity and pest control: Data, tentative conclusions, and new research directions. Environmenta7 Entomo7ogy, 12, 625-629. • Sinha, R.N. (1966) Aerog7yphus robustus, a pest of stored grain. Journa7 of Economie Entomo7ogy, E9, 686-688. Singh, P., Unnithan, G.C. &Delobel, A.G.L. (1983) An artificial diet for sorghum shoot fly larlla'e. Entomo7ogia Experimenta7is et App7icata, 33, 122-124. Steel, R.G.D. & Torrie, J.H. (1980) Princip7es and procedures of statistics, A biometrica7 approach, McGrall-Hill Book Company, New York, 633 pp .

• 138 • Taley, Y.H. &Thakare, K.R. (1979) Biology of seven new hymenopterous parasitoids of Atherigona soccata Rondani. Indian Journal of agricultural Sciences, 49, 344-354. Vandermeer, J. (1989) The ecology of intercropping, Cambridge University Press, New York, 237 pp. Young, W.R. (1981) Fifty-five years of research on the sorghum shootfly. Insect Science and its Application, 2. 3-9. Zongo, J.O., Vincent, C. and Stewart, P..K. 1992. Time-sequential sampl ing of the sorghum shoot fly, Atherigona SGccata Rondani (Diptera: Muscidae), in Burkina Faso. Insect Science and its Application, (In press) . •

. ' • 139

• 8.7. TABLES AND FIGURE 3.

• • • •

Table 22. Abundanee of shoot fIles speeles (male and fema1e) emerged from 1arvae eolleeted from sorghum shoots at Hatourkou, Burkina Faso.

Shoot f1y speeles 1990 1991

Sorghum Sor9hum-Cowpea x' P-values Sorghum Sorghum-Cowpea x' P-values

Atherigona soccata 35 13 10.0S' < 0.005 41 17 9.93' < 0.005 Seoliophlhalmus mieanlipennis 55 43 1. 46 fiS' 0.10 < P < 0.25 63 56 0.41 Ils 0.5< P<0.75 Sflba peelila 4 6 0.40 fiS 0.5

Total 94 62 111 SS

Si9nifleant, P• 0.05, x'test 2 • Not significant, P = 0.05 , x test

b Not available, x2test could not be performed due to Cochran's restriction (i.e. expected frequency < 5).

140 • • •

( \ U

Table 23. Average percent par~~Îtism due ta Trichogrammatoidea simmondsi and lIeotrichoporoides nyemitawus on sorghum shoot fly eggs and larvae in intercropping sorghum-cowpea ln BurkIna Faso.

Cropplng system 1990 1991

r. silMlondsf /1. nyemitawus 1. simmondsi 1/. nyemit awus

Pure sorghum 7.00 .. 6.00 a 11.80 a 12.50 a Sorghum-cowpea 8.75 a 11.75 b 12.30 a 17.50 b P-values 0.250B 0.0037 0.7216 0.0015

• Hean percentages within a column, with dlfferent Jetters are signlflcantly dtfferent,. P = 0.05, AfiOVA •

141 • • •

T.ble 24. Total number of shoot fly parasitoid species collected in Burkina Faso.

Parasitoid species 1990 1991 Pure sorghum Sorghum-Cowpea x' P-values Pure sorghum Sorghum-Cowpea x' P·values

Trichogrammatoidea simmondsi 35 39 0.21 ilS' 0.5 < P < 0.75 47 49 0.04 Ils 0.75 < P < 0.9') Neotrichoporoides nyemitawus 19· 45 10.56· < 0.005 50 70 3.33 ilS 0.05 < P < 0.10 Bracon sp. 3 2 lIA" 2 4 liA Hockeria sp. 2 1 liA 1 1 liA Alysl. sp. 5 2 liA 14 10 0.66 ilS 0.25 < P < 0.5

Tot.1 62 88 113 133

Signifie.nt, P = 0.05, x'test • Ilot signifle.nt P• 0.05, x'test

.. rial availablc, x2test could not be performed due to Cochran's restriction (i.e. expected frequency < 5) .

142 143 •

Figure 3. Percentages of egg and larval parasitism due to Neotrichoporoides nyemitawus and Trichogrammatoidea simmondsi in two cropping systems in Burkina Faso. •

• 1 -0- Pure sorghum , Sorghum-cowpea 1

40 1 1 40 1 1 A) N. nyemltawus, 1990 C) T. slmmonds!, 1990

30 30

20 20

10 -l --' iL ...... ! 10

- - E o 1 r? . ••• • , 1 0 .-III .... 40 .-III 40 eu . B) N. nyemltawus, 1991 1 1 0) T. slmmondsl. 1991 ...eu 1 0- 30J /\ 1 30 ~ 0

20 20

10 10

o1 i • çer Iii 1 i i 1 01 • " ' 1 • l ' i" 1 o 10 20 30 40 50 o 10 20 30 40 50 Days aftar sowing • • • • 144

CONNECTING STATEMENT

In an agroecosystem, all potential natural enemies of a given insect pest should be investigated to identify appropriate candidates for a biocontrol program. In chapter 8, sorne biocontrol agents including egg natural enemies (Trichogrammatoidea simmondsi, Tapinoma sp., Fusarium sp. and Corynebacterium sp.), and the larval parasitoid (Neotrichoporoides nyemitawus) were identified as potential candidates against the shoot fly. Baily and Chada (1968) found that spiders are an important group of predators of sorghum insect pests in Oklahoma • (USA). In Kenya, Delobel and Lubega (1984) pointed out that several unidentified spider genera and species reduced shoot fly eggs ·in sorghum fields. Therefore, l decided to investigate spider populations in Burkina Faso. Because spiders are a complex group of predators with respect to their numbers, species, ecology, and behaviour, l decided to separate chapter 9 from the previous one. The main questions asked in this chapter are: "Which spider species are associated with the shoot fly, and could intercropping sorghum-cowpea increase spider populations?"

• • 145

9 Spi der Fauna in Pure Sorghurn and Intercropped Sorghurn-Cowpea in Burkina Faso . •

In press in Journal of Applied Entomology. • Authors: ZONGO, J.O., STEWART, R.K., VINCENT, C. 146 • 9.1. ABSTRACT Atwo-year study was conducted at Matourkou near Bobo-Dioulasso, Burkina Faso (West Africa), to study spider fauna in pure sorghum and intercropped sorghum-cowpea, Sorghum bico7or L. (Moench)- Vigna ingucu7ata (Walp.), associated with the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae). Sampling was do ne weekly, on six occasions starting 10 days after sowing. Significant differences were observed with respect to the number of individu1ls in the specific composition of spider fauna from different cropping systems. Juvenile spiders represented 84 and 75% of the total number of spiders in 1990 and 1991 respectively. Twelve families and 24 genera were recorded. In pure sorghum, the most important families were Thomisidae (7.73%) and Salticidae (4.12%) whereas Araneidae (15.15%), Theridiidae (8.77%) Thomisidae (8.76%) and Linyphiidae (7.22%) were predominant in sorghum­ • cowpea. In pure cowpea, Linyphiidae (6.69%), Pisauridae (6.18%), and Theridiidae (4.63%) were predominant. Four species were identified: Latrodectus geometricus C.L. Koch, Meioneta prosectes Locket, Pardosa injucunda O.P. Cbr, and Steatoda badia Roewer. Latrodectus geometricus and P. injucunda were only recorded in sorghum-cowpea whereas M. prosectes and S. badia were common to the three cropping systems. Five species namely Araneus sp., M. prosectes, Misumenops sp., Neoscona sp. ,and S. badia showed preference for the intercroppfld sorghum­ cowpea. The Sorenson's index of similarity between sorghum and sorghum­ cowpea, and between cowpea and sorghum-cowpea was 0.75 and 0.66 respectively suggesting that spider species composition was relatively independent of the cropping system. • 147 • 9.2. INTRODUCTION Spiders are an important group of terrestrial predators widely distributed in the world (Nentwig 1987, Nyffeler et al. 1990, Riechert and Lockley 1984, Nyffeler and Benz 1987). There are about 35,000 described species, belonging to about one hundred families (Platnick 1989). Most of the studies of spiders in agroecosystems have been done in North America, Europe, Asia and, to a lesser extent Africa and Australia (Nyffeler and Benz, 1987). Bailey and Chada (1968) studied spider populations in sorghum fields at Oklahoma (USA) and concluded that spiders played an important part in controlling sorghum insect pests. Information on West African spiders is very limited. For instance, reviewing 300 papers on the role of spiders in natural pest control, Nyffeler and Benz (1987) cited only three papers from Egypt • and three from South Africa. Likewise, among the 48 D~pers cited in Nyffeler et al. 's (1990) review concerning spiders as predators of insect eggs, none was African. Millot (1941) studied crab spiders (Thomisidae) in six West African countries including Burkina Faso, Côte d'Ivoire, Guinée, Mali, Niger and Sénégal. In Côte d'Ivoire, Blandin (1971, 1972) stud~ed the spider communities in a savanna grassland and found that peak numbers of both adult and juvenile spiders occurred during the long rainy season. In Kenya, Del obel and Lubega (1984) mentioned that several unidentifieo-'spider genera and species are important predators of the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae) eggs. A. soccata is a key pest of sorghum, Sorghum bicolor L. (Moench), in West Africa (Nwanze, 1985), including Burkina Faso (Bonzi, 1981, • Nwanze, 1988). 148 • Intercropping sorghum-cowpea, Vigna unguicu7ata [L.] Walp. is a commor. practice in Burkina Faso, and it has been suggested that it may increase or decrease natural enemies of some insect pests (Vandermeer, 1989). No work has been published on the effects of intercropping sorghum-cowpea on spider populations. The present experiments were undertaken to study the spider fauna associ ated with sorghum duri ng shoot fly activity and det~rmine if sorghum-cowpea intercropping increases spider populations. 9.3. MATERIALS AND METHODS The study was carried out in 1990 and 1991 at Matourkou, located approximately 10 km from Bobo-Dioulasso, Burkina Faso, West Africa (Il' 11' S, 4' 18'W). Each year, the local sorghum variety "Gnofing" and the cowpea cultivar TVx 3236 were sown on 15 July in a randomized • complete block design with four replicates. Each plot measured 13.5 x 9 m and contained 18 rows. Three cropping systems were established: pure sorghum, 50% sorghum/50% cowpea sown in alternate rows, and pure cowpea. Row spacings were 0.75 m in all plots, whereas intra-row spacings were 0.25 and 0.20 m for sorghum and cowpea, respectively. One and two seedlings were maintained per hill for cowpea and sorghum, respectively. Plots were fertilized with 200 Kg/ha of NPK (1515 15) applied on two occasions, namely 100 Kg/ha at sowing time, and 100 Kg/ha 30 days after sowing. Fifty Kg/ha of urea (46%) were applied 45 days after sowing. Weeding was done on two occasions, 15 and 30 days after sowing. No pesticides were applied during the study. Spider populations were determined by direct observation weekly • on six occasions starting 10 days after sowing. In each plot, five rows 149 • of each crop were randomly selected. The spiders found on these rows were collected by hand using camel brushes and small vials. They were transferred to vials containing 70% alcohol until they were sorted and counted. Data were analyzed using Scheffé's test of the software SuperANOVA (version 1.1 for the Macintosh Computer) (Abacus Concepts Inc., 1989). Sorenson's index of similarity (Sorenson 1948, cited in Krebs 1989) was used to compare species composition between the two crops. The x2 (chi-square) test (Steel and Torrie, 1980) was used to compare the total number of individuals of each species between two crops. Voucher specimens of most spider species were deposited at the Musée Royal de l'Afrique Centrale, Tervuren, Belgium . 9.4. RESULTS • No significant differences of the total number of spiders were observed between cropping system, and per individual crop in 1990 and 1991 (Table 25). However, significant differences of the number of individuals per species were observed between cropping systems (Table 26). The total number of spiders collected (all data pooled) was 221 and 367 in 1990 and 1991, respectively. Several spiders were not identified to species level because the number of spiderl ings was higher (84 and 75% in 1990 and 1991 respectively) than adults (16 and 25% in 1990 and 1991 respectively). Consequently, 194 individual s belonging to 12 families and 24'genera were identified (Table 27). They represented 33% of the total number of spiders collected in 1990 and 1991. In pure sorghum, the most important families were Thomisidae .' (7.73%) and Salticidae (4.12%) whereas Araneidae (15.15%), Theridiidae 150 • (8.77%) Thomisidae (8.76%) and Linyphiidae (7.22%) were predominant in sorghum-cowpea. In pure cowpea, Linyphiidae (6.69%), Pisauridae (6.18%), and Theridiidae (4.63) were predominant (Table 27). Eleven genera were common to cowpea versus sorghum-cowpea whereas la were common to all cropping systems and 12 to sorghum versus sorghum-cowpea (Table 26). Four species were identified: Latrodectus geometricus C.L. Koch, Meioneta prosectes Locket, Pardosa injucunda a.p. Cbr, and Steatoda badia Roewer. Latrodectus geometricus and P. injucunda were only recorded in sorghum-cowpea whereas M. prosectes and S. badia were common to the three cropping systems. Araneus sp., M. prosectes, Misumenops sp., Neoscona sp., and S. badia showed marked preference for the intercropped sorghum-cowpea (Table 26). The Sorenson's index of similarity between sorghum and sorghum­ cowpea, and between cowpea and sorghum-cowpea was 0.75 and 0.66 • respectively. This indicated that species composition of spider communities was more similar when sorghum was compared with intercropped sorghum-cowpea than cowpea compared with sorghum-cowpea. Few spiders were recorded in both cropping systems on the first sampling occasion (ten days after sowing) (Fig. 4). The spiders started to substantially colonize each cropping system from 17 to 45 days'after sowing. In 1990, the peak number of spiders in both cropping systems was recorded 31 days after sowing (Fig. 4). In 1991, the peak number of, spiders in pure sorghum èind in sorghum-cowpea was recorded 31 days after sowing, whereas it was on 38 days aftpr sowing in pure cowpea. • 151 • 9.5. DISCUSSION Thomisidae were common to both cropping systems. We found five genera namely Misumenops, Runcinia, Thomisus, Tmarus, and Xysticus. Millot (1941) described 50 species belonging to 22 genera from six West African countries (Burkina Faso, Côte d'Ivoire, Guinée, Mali, Niger, and Sénégal). He found that the genera Thomisus and Tmar'us contained over 30 and 12 African species respectively. The species Misumenops rubro-decorata Millot, Runcinia depressa Simon, Runcinia proxima voltaensis Millot, Thomisus bidentatus Kulczynski and, Thomisus spinifer Cambridge were collected in Burkina Faso (Millot, 1941). Little information exists on the biology of the four species here reported. A survey of the literature from the scientific database Agricola and Biological Abstracts from 1970 to April 1992 revealed no paper published on these spider species. • In pure sorghum, we found that Salticidae, Thomisidae, and Araneidae were predominant. Studying spider populations in grain sorghum, Bailey and Chada (1968) also found that Lycosidae, Thomisidae, and Salticidae were the most commonly collected families. In Côte d'Ivoire, Blandin (1971, 1972) found that Thomisidae populations were most abundant in a savanna grassland at the beginning of the long rainy season and also in the short rainy season. Prey compos it ion was not q!lant ified. However, it is we11 known that the prey composition varies with the group of spiders (web builders or hunting) (Bishop and Riechert 1990, Culin and Yeargan 1983, Nentwig 1988), the agroecosystem (Agnew and Smith 1989, Bishop and Riechert 1990, Culin and Yeargan 1983, Doane and Dondale 1979, Nyffeler et al. 1989, Young and Lockley 1985), the geographical zones (Nentwig • 1985) and the cultural practices (Buschman et al. 1984). The 152 • intercropped sorghum-cowpea might have influenced prey composition as different spider species were collected per cropping system. Del obel and Lubega (1984) found that spiders sucked the shoot fly egg contents and left conspicuous remman~s of the chorion attached to the sorghum leaves. Nyffeler et al. (1990) also found examples of spiders preying upon the eggs of Araneae and Insecta from North and South America, and Austral ia, largely in agroecosystems and forest ecosystems. They pointed out that spider species found to be predacious on insect eggs belonged principally to the families Salticidae, Oxyopidae, Lycosidae, and Clubionidae which were important families in our studies. ln all cropping systems, spider populations increased until 31 days after sowing. This period corresponded to the susceptible stage of sorghum for shoot fly attack and therefore to high shoot fly activity. The spider populations at that period might have played an important part in reducing shoot fly populations. Although no statistical differences were observed with respect to the total number of spiders, the intercropped sorghum-cowpea increased the number of fi ve speci es namely Araneus sp., M. prosectes, Misumen.ops sp., Neoscona sp.,and S. badia. Studying the bionomics of these species could help to understand their real impact in intercropping sorghum­ cowpea during shoot fly activity. Conservation and augmentation of predators in a given area is an important step in biological control as a maximum control effect is always expected from them (Huffaker and Messenger 1976). Spiders being important predators, great attention must be paid to measures that might be taken to conserve and to increase their numbers. In general, • agricultural practices causing high mortal ity to spiders are 153 • insecticide applications (Dondale et al. 1979, Pfrimmer 1964, Riechert and Lockley 1984), annual harvesting and tilling of the vegetation­ ground layer (Riechert and Lockley 1984, Nentwig 1988), and mechanical disturbance (Bultman and Vetz 1982, Riechert and Lockley 1984). Although more research should be done to understand the effect of spiders in reducing shoot fly populations, intercropping sorghum-cowpea could be practiced to increase the number of certain spider species namely Araneus sp., Meioneta prosectes, Misumenops sp., Neoscona sp., and Steatoda badia .

•

• 154 • 9.6. REFERENCES Abacus Concepts Inc. 1989. SuperANOVA, accessible general linear modeling. Berkeley, CA., 316 p. Agnew, C.W. and Smith, Jr. J.W. 1989. Ecology of spiders (Araneae) in a peanut agroecosystem. Environ. Entomo7. 18: 30-42. Bailey, C.L. and Chada, H.L. 1968. Spider populations in grain sorghum. Ann. Entomo7. Soc. Am. 61: 567-571. Bishop, L. and Riechert, S.E. 1990. Spider colonization of agroecosystems: mode and source. Environ. Entomo7. 19: 1738-1745 Blandin, P. 1971. Recherches ëcologiques dans la savane de Lamto (Côte d'Ivoire): observations prëliminaires sur le peuplement aranëologique. Terre Vie 118: 218-239. Blandin, P. 1972. Recherches ëcologiques sur les araignëes de la savane de Lamto (Côte d'Ivoire): premières donnëes sur les cycles des • Thomisidae de la st~ate herbacëe. Ann7s Univ. Abidjan (E) 5: 241­ 264. Bonzi, S.M. 1981 Fl uctuations sai sonni ères des popul ati ons de la mouche des pousses de sorgho en Haute-Volta. Insect Sci. Applic. 2: 59-62. Bultman, T.L.and Vetz, G.W. 1982. Abundance and community structure of forest floor spi ders fa 11 owi ng l itter man i pul ation. Oeco 7ogi a 55: 34-41. Buschman, L.L.; Pitre, H.N. and Hodges, H.F. 1984. Soybean cultural practices: effects on populations of Geocorids, Nabids, and other soybean arthropods. Environ. Entomo7. 13: 305-317. Culin,J.D. and Yeargan, K.V. 1983. Comparative study of spider communities in alfalfa and soybean ecosystems: foliage-dwelling • spiders. Ann. Entomo7. Soc. Am. 76: 825-831. 155 • Delobel, A.G.L. and Lubega, M.C. 1984. Rainfall as a mortality factor in th!! sorghum shootfly, Atherigona soccata Rond. (Diptera, Muscidae). Z. ang. Entomol. (J. Appl. Entomol.) 97: 510-516. Doane, J.F. and Condale, C.D. 1979. Seasonal captures of spiders (Araneae) in a wheat field and its grassy borders in central Saskatchewan. Cano Ent. 111: 439-445. Dondale, C.D.; Parent, B. and Pitre, D. 1979. A6-year study of spiders (Araneae) in a Quebec apple orchard. Cano Ent. 111: 377-380. Huffaker, C.B. and Messenger, P.S. 1976. Theory and practice of biological control. Academic Press, New York, 788 p. Krebs, C.J. 1989. Ecological methodology. Harper &Row Publishers, New York, 654 p. Millot, M.J. 1941. Les araignées de l'Afrique Occidentale Française: Thomisides. Académie des Sciences de l'Institut de France. • Mémoires, T. 65, 82 pp. Nentwig, W. 1985. Prey analysis of four species of tropical orb-weavi~g spiders (Aranea: Araneidae) and a comparaison with araneids of the temperate zone. Oeco7ogia 66: 580-594. Nentwig, W. 1987. Ecophysiology of spiders. Springer-Verlag. Berlin, 448 p. Nentwig, W. 1988. Augmentation of beneficial arthropods by strip­ management. 1 succession of predacious arthropods and long-term change in the ratio of phytophagous and predacious arthropods in a meadow. Oeco7ogia 76: 597-606•

• ' 156 • Nwanze, K.F. 1985. Sorghum insect pests in West Africa pp. 37-43, In International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). Proceeding of the International Sorghum Entomology Workshop, 15-21 July 1984. Texas A & M University, College Station, TX, USA. Patancheru, A.P. 502324 India: ICRISAT. Nwanze, K.F. 1988. Distribution and seasonal incidence of some major insect pests of sorghum in 8urkina Faso. Insect Science and its App7ication, 9: 313-321. Nyffeler, M. and Benz. G. 1987. Spiders in natural pest control: A review. J. App7. Ent. 103: 321-339. Nyffeler, M., Dean, D.A. and Sterling, W.L. 1989. Prey selection and predatory importance of orb-weaving spiders (Aranae: Araneidae, Uloboridae) in Texas cotton. Environ. Entomo7. ~8: 373-380• Nyffeler, M., Breene, R.G.; Dean, D.A. and Sterling, W.L. 1990. Spiders • as predators of arthropod eggs. J. App7. Ent. 109: 490-501 Pfrimmer, T.R. 1964. Populations of certain insects and spiders on cotton plants following insecticide application. J. Econ. Entomo7. 57: 640-644. Platnick, N.I. 1989. Advances in spider taxonomy 1981-1989: A

suppl ement to Bri gnoli 1 s A catalogue of the Araneae descri bed between 1940 and 1981. Manchester University Press, New York. 673 pp. Riechert,S.E. and Lockley, T. 1984. Spiders as biological control agents. Annu. Rev. Entomo7. 29: 299-320. Sorenson, T. 1948. A method of establishing groups of equal amplitude in plant sociology base~ on similarity of species centent. Kong. • Dan. Vidensk. Se7sk. Bio7. Skr. 5: 1-34 . 157 • Steel, R.G.D. & Torrie, J.H. 1980. Principles and procedures of statistics, Abiometrical approach, McGraw-Hill Book Company, New York, 633 pp. Vandermeer J. H., 1989. The ecology of intercroppi ng. Cambridge University F~"':,s, New York, 237 p. Young, a.p. and Lockley, T.C. 1985. The striped lynx spider, Oxyopes sa lticus (Araneae: axyopidae) in agroecosystems. Entomophaga 30: 329-346 .

•

• • 158

• 9.? TABLES AND FIGURE 4

• • 159

Table 25. Mean number of spiders (spiderlings and adults, all species confounded) per five rows collected in two cropping systems in Burkina Faso.

Crop 1990 1991

Pure Intercropped Pure Intercropped • Sorghum 13.50 a• 14.00a 23.75 a 24.00a Cowpea 15.75 a 12.00a 24.00 a 26.00a

* Horizontally (pure vs intercropped), mean percentages with same letters within the same year are not significantly different, Scheffé's test, P = 0.05 .

• • ., ••

Table 26. iotal number of spider species (spiderlings and adults) collected in two cropping systems in Burkina Faso in 1990 and 1991 (n = 156, identified to at least genus).

Sorghum towpea Spider species Pure Intercropped X2 Pure Intercropped x2

Araneus sp. 4 13 4.76' 1 13 101,28' Aranfe71a sp. -- 1 - NA Chiracanthfum sp. - 1 NA" - - - C/ubfona sp. 3 5 NA 2 5 NA Cyrtophora sp. -- - 1 - NA Euryopis sp. -- - - 1 NA Hfppasa sp. - 2 NA - 2 NA Latrodectus geomftrfcus - 1 NA - 1 NA Leucauge sp. - 5 NA - 5 NA Herennius sp. 1 - NA - - - Hefoneta prosectes 2 Il 6.23' 10 Il 0.04, Hfsumenops sp. Il 9 0.20, 1 9 6.40, Neoscona sp. 2 12 7.14 1 12 6.40 Oxy~pes sp. 1 3 NA 1 3 NA Pardosa fnjucunda .. 1 NA - 1 NA Phflodromus sp. 1 1 NA 2 l NA Runcfnia sp. - 1 NA , - 1 NA Steatoda badfa 1 13 10.28 7 13 1.8 Thanatus sp. 1 2 NA - 2 NA Therfdion sp. 2 2 NA 2 2 NA Thomfsus sp. 1 2 NA - 2 NA Tmarus sp. - 3 NA 1 3 NA Tybaertie//a sp. - - - 3 - NA Xysticus sp. 3 2 NA 1 2 NA

* Significant, P < 2.05, x2 test . ** Not applicable, X test could not be performed due to Cochran's restriction (i.e. expected frequency < 5) •

160 161 Table 27. Relative abundance of spider families and species collected in three • cropping systems in Burkina Faso in 1990 and 1991.

Percenta~e of total captures (n- 194, ldentified to at least family)

Family Pure sorghum Sorghum-cowpea Pure cowpea Species

Araneidae (Orb weavers) 3.09 15.45 2.08 Araneus sp. 2.06 6.70 0.52 AranieH ~ sp. 0.52 Cyrtophora sp. 0.52 Leucauge sp. 2.57 Neoscona sp. 1.03 6.18 0.52 Clubionidae (foliage spiders) 1.54 3.09 1.03 Chiracanthium sp. 0.52 C7ubiona sp. 1.54 2.57 1.03 Corinnidae 0.52 Merennius sp. 0.52 Gnaphosidae (Ground spiders) 0.52 0.52 0.52 Unidentified species 0.52 0.52 0.52 Linyphiidae (Line weavers 1.03 7.22 6.69 Meioneta prosectes Locket 1.03 5.67 5.15 Tybaertie77a sp. 1.54 Lycodidae (Wolf spiders) 1.55 Hippasa sp. 1.03 Pardosa injucunda (O.P. Cbr. ) 0.52 • Oxyopidae (Lynx spiders) 0.52 1.54 0.52 Oxyopes sp. 0.52 1.54 0.52 Philodomidae (Running crab spiders) 1.04 1.55 1.03 Phil odromus sp. 0.52 0.52 1.03 Thanatus sp. 0.52 1.03 Pisauridae }NUrsery-web spiders) 1.03 2.57 6.18 Unidenti ied species 1.03 2.57 6.18 Salticidae }JUmping spiders) 4.12 1.03 2.57 Unidenti ied species 4.12 1.03 2.57 Theridiidae (Comb-footed spiders) 1.55 8.77 4.63 Euryopis sp. - 0.52 Latrodectus geomitricus C.L.Koch 0.52 Steatoda badia Roewer 0.52 6.70 3.60 Theridion sp. 1.03 1.03 1.03 Thomisidae (Crab spiders) 7.73 8.76 1.56 Misumenops sp. 5.67 4.64 0.52 Runcinia sp. 0.52 Thomisus sp. 0.52 1.03 Tmarus sp. 1.54 0.52 Xysticus sp. 1.54 1.03 0.52

% of total captures (n -194) 22.69 50.50 26.81 • 162 •

Figure 4. Total spider numbers (spiderlings and adults) per five rows in three cropping systems in Burkina Faso •

• 0 Pure sorghum Sorghum-cowpea ~ Pure co ea • 60 A) 1990 50

40 :::en 0 :l0- 30 G) > :;:: 20 :l0- G) C. en 10 :l0- G) "C.- 0 c. en -0 60 :l0- G) • B) 1991 ..c E 50 ~ l:: -ca 40 -0 1- 30

20 .L;~~ 10

0 " 1 10 17 24 31 3B 45 • Days after sowing • 163

CONNECTING STATEMENT

In biological control, no natural enemy can be used without sorne knowledge of its biology. Answering important questions such as which instar of the host is preferred, as well as other aspects of parasitism may help to implement control tactics. In chapter 8, l suggested that Neotrichoporoides nyemitawus could reduce shoot fly larval populations. l also concluded that intercropping sorghum-cowpea would increase N. nyemitawus populations. Taley and Thakare (1979) studied the life­ history of N. nyemitawus in India, but no informati~n exists on how to • rear this par~sitoid and which instar of the shoot fly is preferred. Therefore, this chapter deals with how to rear N. nyemitawus, with an emphasis on host stage preference and searching behaviour .

• • 164

10 Parasitism of sorghum shoot fly larvae, Atherigona soccata Rondani (Diptera: Muscidae), by Neotrichoporoides nyemitawus Rohwer (Hymenoptera: Eulophidae) • •

Submitted to Insect Science and its Application, July 1992. • Authors: ZONGO, J.O., STEWART, R.K., VINCENT, C. 165 • 10.1. ABSTRACT Larval parasitism of the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), by Neotrichoporoides nyemitawus Rohwer (Hymenoptera: Eulophidae) was studied in the laboratory. Ten shoot fly larvae of each instar (3) and two periods of exposure (24, 48 h) were used in a factorial design with four replicates. Significant differences of parasitism were observed with respect to instars, periods of exposure, and the interaction instar - period of exposure. The second larval instar was most parasitized (68.75 and 85% of parasitism after 24 and 48 h respectively) fcllowed by the first instar (46.25% of parasitism) exposed after 48 h to adult parasitoids. N. nyemitawus was an effective shoot fly endo-larval parasitoid. Observations on N. nyemitawus searching sorghum seedlings for shoot fly • larvae are summarized .

• 166 • 10.2. INTRODUCTION The sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), is an important pest of sorghum, Sorghum bico7or (Linne, Moench), in West African countries (Nwanze 1985, Gahukar 1990) and in Asia (Young 1981). Although much work has been done on control strategies for the shoot fly (Young 1981), biological control remains a relatively unexplored strategy. The shoot fly has a wide range of natural enemies including Neotrichoporoides nyemitawus Rohwer (Hymenoptera: Eulophidae) which is a widespread endo-larval parasitoid. N. nyemitawus was first described by Rohwer (1921) as Tetrastichus nyemitawus. Under this name, the parasitoid has been recorded on Atherigona spp. in India (Rawat and Sahu 1968, Kundu and Kishore 1972, Taley and Thakare 1979) and in Kenya (Delobel, 1983). In a revision of the European • Tetrastichinae (Hymenoptera: Eulophidae), De V. Graham (1987) replaced the genus Tetrastichus by Neotrichoporoides Girault. Although Taley and Thakare (1979) studied the life-history of N. nyemitawus, little information exists on host stage preference and the parasitoid's searching behavior. The present work was undertaken to determine which instar of A. soccata is preferred for attack and how long the parasitoid takes to parasitize shoot fly larvae. The searching behavior of N. nyemitawus is also summarized. Such information could be important for implementing a biological control program based on N. nyemitawus. • 167 • 10.3. MATERIALS AND METHODS The study was carried out in a rearing room set at 26 (± 1) ·C, 75% R.H. (± 2) and 12:12 (L/D). Fourteen day-old sorghum plants from sowing were grown in 18 cm diameter plastic pots. 8efore transferring shoot fly larvae and parasitoids to the plants, the pots were covered with a transparent plastic sheet (40 x 40 cm) held in three places (upper part of the pot; middle and upper parts of the plastic sheet), by clamp collars to form a cylindrical cage. The upper part of the cage was capped with fine muslin. A square hole (10 x 10 cm) was made on the basal part of the cage to allow diet replacement. Ten shoot fly larvae of each instar were used in a factorial design with four replicates. The three instars were defined according to Deeming (1971) and Raina (1981) descriptions. Larvae of each instar were exposed to N. nyemitawus adults for two periods of exposure: 24 and 48 h. They • were transferred into the central shoot of the plants with a fine camel brush. After transferring the larvae, a two day-old mated female adult N. nyemitawus was placed in each cage. To obtain two day-old female parasitoids, newly emerged females on the same day were kept in a separate cage with two > 24 h old males. Adult parasitoids were fed on a medium consisting of 1/3 honey and 2/3 distilled water. A 5 cm diameter Petri dish containing cotton with distilled water was also put in the cage. The diet was replaced every second day. After each treatment, the sorghum plants were removed and dissected. Each shoot fly larva was then removed and transferred to 30 ml plastic cups with perforated lids (model Priee Daxxion, Saint-Laurent, Québec, Canada) containing 1 9 of Singh's et al. (1983) diet. The diet was replaced every second day . ' • Observations were made daily untn the parasitoids emerged. 168 • Larvae dyi ng in the course of the experiments were di ssected in Ringer's solution to detect the presence of eggs, larvae or pupac of the parasitoids. To study the searching behavior of female N. nyemHawus, one parasitoid female was placed in a cage containing five sorghum plants and one to two day-old second instar of shoot fly as follow: 1) five larvae on each sorghum plant, 2) five larvae placed on the soil adjacent to the sorghum plants, and 3) five larvae placed on the soil near a 10 x 20 mm piece of sorghum leaf. Treatments were repeated nine times. Observations were made for one hour on how the adult female explored the plant, inserted its ovipositor as well as the time required to move From one plant to another. A cage containing up to two day-old N. nyemitawus adults (males and females) was used to provide material for dissection. Second and • third intars shoot fly larvae were placed on the sorghum plant. After exposure to adult parasitoid females, larvae were dissected daily ln Ringer's solution to observe the number of eggs laid, larvae and pupae. The number of days from 1) the date of infestation to the death of A. soccata larvae, 2) the date of infestation to the emergence of adult parasitoids, 3) the time from death of A. soccata larvae to· adult parasitoid emergence, and 4) the longevity of adult parasitoids were recorded . Specimens were identified by Dr. J. Lasalle from the International Institute of Entomology, London. Voucher specimens were deposited in the Lyman Museum, Macdonald Campus of McGill University, Sa inte-Anne de Bellevue, Québec, Canada, and at the Bi osystematic Research Center, Ottawa, Canada. • Data were analyzed using ANOVA two factors and Scheffé's test of 169 • the software SuperANOVA (version 1.1 for the Macintosh Computer) (Abacus Concepts Inc. 1989). 10.4. RESULTS Significant differences of parasitism were observed with respect to instars (F = 217; df = 2, 18; P < 0.0001), period of exposure (F =

44.37; df = l, 18; p < 0.0001) and the interaction instars - period of exposure (F = 34.94; df = 2, 18; P < 0.0001) (Table 28). The second instar was most heavily parasitized, followed by the first instar exposed 48 h (Table 28). Table 29 gives the mean number of days from oviposition to adult emergence; from egg to A. soccata larval death; from time of A. soccata parasitized larvae dying to adult emergence; from egg to adult mortality and the life span of adults. The parasitoid female used its antennae to explore the sorghum plant. She started to inspect leaves adjacent to the point of exit of • the central shoot. She sometimes entered the central shoot to detect the presence of a shoot fly l arva. When a l arva was l ocated, the parasitoid started probing for a ho st by applying its ovipositor tip to the plant tissues. She then bent her abdomen and stroked the plant several times (8 to 13) with her ovipositor. If there was a resistance to penetration, the female moved the ovipositor around the sorghum plant stem until she found a suitable penetration site. She then inserted her ovipositor into the plant tissues. Exploring and oviposition after plant penetration usually took about 10 minutes and then the female would relocate. During oviposition, the female held the plant ~lith all six legs, the fore and middle legs being less mobile' than the hind legs. Although we did not quantify the time spent by the female parasitoid on each sorghum plant part, sorghum stems received • more.search time than leaves. Upper leaves were used for resting wh en 170 • the parasitoid fini shed laying an egg. In general, foraging on the sorghum plant started from top to bottom, the larva being found usually in the base of the plant. The behavior of N. nyemitawus was characterized by continuous movements, turning, and exploring the whole plant from top to bottom with its antennae. This behavior may be divided in four phases: 1) exploring, 2) ovipositor insertion, 3) oviposition, and 4) resting. There was neither attraction nor attack when larvae were exposed on the soil. When a piece of leaf was put adjacent to a larva, the female parasitoid flew around but never touched the larvae. Wh en larvae crawled and entered into the central shoot, the female started to examine the sorghum plant. Usually one egg was laid per larva, but two eggs per larva were observed once in 30 observations. The egg was deposited between the • 7th and 8th abdominal segments of the shoot fly larva. No A. soccata adult emerged from parasitized larvae. Parasitoid pupa occupied the whole body of the shoot fly larva, leaving about 0.3 to 0.5 mm in each extremity. 10.5. DISCUSSION The first and second instars of the shoot fly last 1- 3 days at 30° C (Raina, 1981). This suggests that at 26 ·C, the first and second instars parasitized would still remain in their instar by the time they were parasitized. The high rate of parasitism of second and, to a lesser extent, third instars indicated that the female parasitoid can distinguish the size ·of its hosto The first-instars are smaller and more slender than second and third instars (Raina, 1981), and size is a physical cue used by insect parasitoids in ho st selection and • location (Vinson, 1985). The lack of attraction to the first instar and 171 • the low percentage of parasitism on third instar, suggested that the size of shoot fly larva is used as a physical cue. Richerson and DeLoach (1972) also found that different sized beetles influenced the choice of Peri7itus coccine77ae Schrank (Braconidae). Other physical cues used by insect parasitoids inc1ude sound, vi bration, shape, texture and electromagnetic radiation (Vinson, 19B5). Movements of the shoot fly larva in the sorghum stem might stimulate the parasitoid in ho st attack. Another physical cue might be the sorghum plant itself, as no larva moving outside the sorghum stem was examined or attacked by N. nyemitawus. Insects often use environmental cues (abiotic and biotic factors) to direct their searching when cu es from resources cannot be detected (Bell 1991). For instance, females of Diaeretie77a rapae Mclntosh (Braconidae), parasitoids of cabbage aphid, Brevicoryne brassicae L. are attracted by plant odour, and col our, of the leaves • (Bell, 1991). The pieces of leaves here put adjacent to A. soccata larvae might have stimulated N. nyemitawus searching. Chemical cu es play the greatest role in host location by parasitoids (Vinson 1985, Vet and Dicke 1992), physical factors being more important at host examination level (Vinson, 1985). Vet and Dicke (1992) reviewed the ecology of infochemical used by natural enemies and stated that herbivores have to feed and defecate, resulting in emission of volatiles that may attract parasitoids. Although these mechanisms have not been investigated in this study, a characteristic odor escaping from the dead heart was noted. More detailed a:ld critical experimentation is required to determine the nature of both physical and ehemieal eues in the case of N. nyemitawus. The eharaeteristic odor from the dead heart might be an important eue to investigate. • The duration of life-eyele. parameters of N. nyemitawus sueh as 172 • the mean number of days from oviposition to adult emergence, from egg to adult mortality and the life span of adults here reported may help to implement the use of programmed releases i.e. timing of releases. After the parasitoid laid its eggs, the A. soccata larva took 5 to 12 days (average = 8, n = 30) to die. Taley and Thakare (1979) reported that the shoot fly larvae became inactive when the parasitoid larva was in its third or fourth instar. This clearly indicates that dead heart formation cannot be avoided before or after shoot fly larva parasitization, as damage is still done by the parasitized larvae. The cage and the medium were effective in rearing N. nyemitawus adults as the average life span was 21.65 days. The maximum life span of an adult female parasitoid was 51 days. Neotrichoporoides nyemitawus was an effective shoot fly endo­ larval parasitoid as no adult shoot flies emerged from parasitized • larvae. Zongo et al. (1992) concluded that shoot fly control methods should be implemented before dead heart formation. Although N. nyemitawus cannat prevent dead heart formation, it may be of potential use in reducing shoot fly populations during a cropping season.

• 173 • 10.6. REFERENCES Abacus Concepts Inc. (1989) SuperANOVA, Accessible General Linear Modelin9, Berkeley, California, 316 p. Bell, W.J. (1991) Searchin9 behaviour. The behavioural ecology of finding resources. Chapman and Hall, London, 358 pp. Deeming, J. C. (1971) Sorne species of Atherigana Rondani (Diptera: Muscidae) from Northern Nigeria, with special reference to those injurious to cereal crops. B~77. Entama7. Res., 61, 133-190. Del obel , A. (1983) Etude des facteurs déterminant l'abondance des populations de la mouche du sorgho, Atherigana saccata Rondani (Diptères, Muscidae). Thèse de Doctorat d'Etat, Université de Paris Sud, Centre d'Orsay. ORSTOM, Paris, 127 pp. De V. Graham, M.W.R. (1987) A reclassification of the European Tetrastichinae (Hymenoptera: Eulophidae), with a revision of • certain genera. Bu 77 • Brit. Mus. (Natura7 Histary), EntamaI. Series 55, 55-69. Gahukar, R.T. (1990) Overview of insect pest management in cereals crops in sub-Saharan West Africa. Indian J. Entama7. 52, 125­ 138. Kundu, G.G. and Kishore, P. (1972) New ho st record of Atherigana naqvii Steyskal (Anthomyiidae: Diptera) from India t0gether with new record of its three Hymenopterous parasites. l ndi an J. Entama7. 34, 80-81. Nwanze, K.F. (1985) Sorghum insect pests in West africa pp. 37-43, In International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). Proceedings of the International Sorghum Entomology Workshop, 15-21 July 1984. Texas A & M University, College' .' Station, TX, USA. Patancheru, India. 174 • Raina, A.K. (1981) Movement, feeding behaviour and growth of larvae of the sorghum shoot fly, Atherigana saeeata. Inseet. Sei. Applie. 2, 77-8l. Rawat, R.R. and Sahu, H.R. (1968) New records of Tetrastiehus nyemitawus Rohwer (Hymenoptera: Eulophidae) as a parasite of Atherigona sp., the wheat stem fly in Madhya Pradesh. Indian J. Entamai. 3D, 319. Richerson, J.V. and DeLoach, C.J. (1972) Sorne aspects of hast selection by Perilitus eaeeinellae. Ann. Entamai. Sac. Am. 65, 834-839. Rohwer, S.A. (1921) Descriptions of new chalcidid flies from Coimbatore (S. India). Ann. Mag. Nat. Hist 7, 123-135 [Rev. Appl. Ent. (A): 136]. Singh, P., Unnithan, G.C. and Delobel, A.G.L. (1983) An artificial diet for sorghum shoot fly larvae. Entomol. Exp. Appl. 33, 122­ • 124. Taley, Y.M. and Thakare, K.R. (1979) Biology of seven new hymenopterous parasitoids of Atherigana soeeata Rondani. Indian J. agrie. Sei. 49, 344-354. Vet, L.E.M. and Dicke, M. (1992) Ecology of i nfochemi cal use by natural enemies in a tritrophic context. Annu. Rev. Entamai. 37, 141-172. Vinson, S.B. (1985) The behavior of parasitoids, pp. 417-469. III Kerkut, G.A. and Gilbert, L.I. (eds.). Comprehensive Insect Physiology Biochemistry and Pharmacology. Vol. 9, Behaviour. Pergamon Press, New York. • 175 • Young, W.R. (1981) Fifty-five years 0; research on the sorghum shootfly. Inseet Sei. App7ie., 2, 3-9. Zon90, J.O., Vincent, C. and Stewart, R.K. (1992) Time-sequential sampl ing of the sorghum shoot fly, Atherigona soeeata Rondani (Diptera: Muscidae), in Burkina Faso. Inseet Sei. App7ie. (ln press) .

•

• • 176

10.7. TABLES •

• • 177

Table 28. Mean percentages of larval parasitism in relation to period of exposure to Neotrichoporoides nyemitawus.

A. soccata larval stage/ % parasitism' Standard time of exposure (h) (n • 10 larvae Error per replicate)

First instar 24 0.00 0.00 48 46.25 5.15 Second instar • 24 68.75 4.27 48 85.00 2.04 Third instar 24 17 .50 3.22 48 8.75 2.39

, Mean of 4 replicates; F-value of the interaction larval instar-time of exposure being 34.94; df = 2, 18; and p < 0.0001 .

• • 178

Table 29. Ouration of l ife-cycle parameters of Neotrichoporoides

nyemitawus in the l aboratory (26 (± 1) 0 C, 75% R.H. (± 2) and 12:12 (llO).

Mean duration Standard life-cycle stage in days (n z 30) error

Egg to adult emergence 20.33 4.77

Egg to A. soccata parasitized 8.06 2.37 • larva dying A. soccata parasitized larval 11.43 0.66 mortality to adult emergence

Egg to adult mortality 41.50 12.42

Adult l ife span 21.56 10.41

• • 179

CONNECTING STATEMENT

In chapter 4, l concluded that sorghum shoot fly control measures should be taken before dead heart formation. In Chapter 8, l found that Trichogrammatoidea simmondsi Nagaraja (Hymenoptera: Trichogrammatidae), an egg parasitoid, could reduce shoot fly eggs during the susceptible stage of sorghum. Seven to 12% of the sorghum shoot fly eggs were parasitized by Tri chogrammatoidea simmondsi. It has been postul ated that thi s egg • parasitoid could be a potential biocontrol agent against the shoot fly. When a potential biological control agent is identified, research on its biology is essential to understand how. to establish a control program. Chapter Il deals with the first study on the biology of T. simmondsi. The objective is to determine the number of instars, adult life span and ho st preference.

. ' • 180

Il Biology of Trichogrammatoidea simmondsi Nagaraja (Hymenoptera: Trichogrammatidae) on sorghum shoot fly, Atherigona soccata Rondani (Diptera: Huscidae) eggs •

Submitted to Entomophaga, July 1992. Authors: ZONGO, J.O., STEWART, R.K., VINCENT, C. • 181 • 11.1. Abstract Experiments were conducted in a rearing room to study the biology of Trichogrammatoidea simmondsi Nagaraja (Hymenoptera: Tri chogrammatidae) on sorghum shoot fly, Atherigona soccata Rondan i (Diptera: Muscidae) eggs. Shoot fly eggs were divided in two groups: 1) eggs < 24 h old and, 2) > 24 h old eggs. Thirty eggs of each group were used in a randomized complete block design with four replicates. Shoot fly eggs less than 24 h old were preferred (73% of parasitism) over 24 h old eggs (7.25%). Three larval instars of T. simmondsi were observed. Few eggs with two T. simmondsi exi t ho les (1. 87%) were recorded in > 24 h old eggs compared with < 24 h ones (3.74%). The sex ratio male:female was 1:1.47. The development from oviposition to adult emergence ranged from 7 to 12 days (average = 9.8 ± 1.31, n = 40), and the average life span of male and female T. simmondsi was 25 ± 1.46 h, • (range 22 - 26 h, n = 12) and 35.17 ± 10.9 (range 25 - 50 h, n = 28) respectively at 26' C, 60-65% R.H. and 12:12 (LlO) photoperiod. This paper constitutes the first published information on the biology of T. simmondsi on the sorghum shoot fly.

• 182 • Il.2. Introduction The Trichogrammatidae, whose species attack eggs of various insects, is a large Family of economi c importance (Nagarkatti and Nagaraja, 1977). The genus Trichogrammatoidea contains about 18 species recorded from different countries (Nagarkatti and Nagaraja, 1977) . Pi ntureau and Babault (1988) listed six Afri can speci es including Trichogrammatoidea simmondsi Nagaraja which has been recorded in Ghana and Malawi. Feijen and Schulten (1981) recorded T. simmondsi on eggs of Diopsis macrophtha7ma Dalm. (= thoracica Westwood) (Diptera: Diopsidae), an insect pest of rice in Malawi. They also found that other rice insect pests such as Chi70 parte77us Swinhoe (Lepidoptera: Pyralidae) and Sepedon angu7aris (Diptera: Sciomyzidae) were alternative hosts of T. simmondsi. T. simmondsi was also recorded on sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae) eggs • in Burkina Faso (Zongo et a7. unpublished data). Establishing a time­ sequential sampling plan for the sorghum shoot fly, Zongo et a7. (1992) concluded that control measures against A. socci!ta should be taken before de ad heart formation. Studying the effect of intercropping sorghum-cowpea on natural enemies of A. soccata, (Zongo et aJ. unpublished data) found that egg natural enemies such as Trichogrammatoidea simmondsi, T. bactrae, Trichogramma spp., Tapinoma sp. (Hymenoptera: Formicidae), Abro7ophus sp. (Acari: Erythraeidae), Fusarium sp., and Corynebacterium sp., could be appropriate candidates as they prevent the eclosion of shoot fly larvae, which are responsible for de ad heart formation. They found 7 to 12.30% of eggs parasitism caused by T. simmondsi in the field and postulate that T. simmondsi could be a potential biological control agent against A. soccata. • No work has been published on the biology of this parasitoid on 183 • A. soccata. Therefore, the present study was carried out to provide basic information for use in a biological control program against the sorghum shoot fly. Il.3. Materials and Methods Experiments were conducted in an incubator set at 26° C, 60-65% R.H. and 12:12 (L/D) photoperiod. Parasitoids were obtained at Matourkou from shoot fly eggs collected from sorghum fields SONn at weekly intervals. The eggs were placed on a piece (1.5 x 8 cm) of filter paper wetted with 10 droplets of distilled wa'~r, inserted in vials (5 x 10 cm) and kept in the incubator. To feed emerging adults, a diet comprising 1/3 honey and 2/3 distilled water was streaked inside the vials using a fine camel brush. Adult parasitoids emerging on the same day were transferred to a common vial using a fine camel brush. • A. soccata adults were obtained by rearing third instar larvae using Singh et a7.'s (1983) diet. Third instar larvae from the field were identified using Deeming's (1971) and Raina's (1981) descriptions. A. soccata adults were maintained using Soto's (1972) methods. Sorghum plants were grown in 18 cm diameter plastic pots. To obtain shoot fly eggs, a plastic pot containing five to ten 14-day old sorghum plants was kept in 40 x 40 x 40 cm screened cage in an insectarium. Five to ten A. soccata females were then released between 7:00 and 8:00 h in each cage for egg laying. After laying, the eggs were divided in two groups: 1) eggs < 24 h old and, 2) > 24 h old eggs. To obtain > 24 h old eggs, the sorghum plants were removed from the cage after egg laying and transferred in another cage without A. soccata females for 24 h. Thirty eggs of each group were used in a randomized complete • black design with four replicates. Each group of eggs was kept in 5 x 184 la cm vials. The eggs were exposed to two couples of T. simmondsi • adults of the same age until the parasitoids died. Shoot fly larvae and parasitoids emerging from eggs were recorded. Two weeks after egg exposure to the parasitoids, all remaining eggs were dissected in Ringer's solution using two fine pins under a binocular microscope to detect unemerged parasitoids. To study the development of the parasitoid, 40 parasitized shoot fly eggs were kept each in a 2.5 x 9.5 cm vial. The number of days from egg to adult emergence and from adult emergence to adult mortality was recorded per hour from 7 to 12 h and from 15 to 17 h. To distinguish instars, parasitized eggs of the same age were dissected daily; larvae were removed and larval instars identified using the length, col our and form. Pupae were removed and described. Specimens were identified by Dr. B. Pintureau, INSA, • Vi 11 eurbanne, Lyon, France. Voucher specimens were deposited at the Lyman Museum, Macdonald College of McGill University, Sainte-Anne de Bell evue, Québec, and at the Bi osystematic Research Center, Ottawa, Canada. Data were analyzed using Scheffé's test of the software SuperANOVA (version 1.1 for the Macintosh Computer) (Abacus Concepts Inc. 1989). 11.4. Results The T. simmondsi egg is white and fusiform. The larva is white with the posterior end bulged and becomes more opaque with age. Three instars were observed. The first instar is more slender than the second. The second instar is shorter and thicker than the third instar. The third instar can be distinguished from the second by the dark color • well developed in the posterior part and by the size. In first and 185 • second instars, the segmentation is not clear. The third instar has a distinct head. The pupa is exarate ar,d distinct. The eyes and ocell i are red. Wh en there were two individuals per A. soccata egg, the pupal heads were orientated to each pole of the egg or opposed to other. Significant differences were observed with respect to egg age (F = 344; df = 1,3; P < 0.0001). Eggs less than 24 h old were more successfully parasitized (73%) than those > 24 h old (7.25%) (Table 30). Two days after parasitization, A. soccata eggs became more opaque. Table 31 shows the size of T. simmondsi immature stages. Fewer eggs with two exit holes were recorded in > 24 h old eggs compared with < 24 h old eggs (Table 30). The averall sex ratio male:female was 1:1.47 . The duration of each stadium was not measured, but the • development time from egg to adult emergence ranged from 7 to 12 days (avel'age = 9.8 ± 1.31, n = 40). The average life span of male and

female T. simmondsi was 25 ± 1.46 h, (range' 22 - 26 h, n = 12) and 35.17 ± 10.9 (range 25 - 50 h, n = 28) respectively. Il.5. Discussion Trichogrammatoidea simmondsi successfully parasitized shoot fly eggs aged less than 24 h old. Specifie colors are included in electromagnetic radiation and are used as physical eues by parasitoids (Vinson, 1985). A. soccata eggs aged less than 24 h old were whiter than older ones. This difference could be a physical cue used by the parasitoid to distinguish its hosts. Takahashi and Pimentel (1967) also reported that Nasonia vitripennis Walker preferred black housefly pupae over brown ones •

' • We observed at most two exit holes of T. simmondsi per egg. 186 • However, longe et al. (unpublished data) recorded up to three holes (1.63%, n = 305) from eggs collected in the field. This suggests that superparasitism may be more prevalent in the field than in laboratory conditions. The sex ratio (40.5% males, 59.5% females) recorded in this study is similar to that observed by longe et al. (unpublished data) from eggs collected in the field at Matourkou (44 %males, 56% females in 1990, and 42% males, 58% females in 1991). Feijen and Schulten (1981) found that laboratory eggs of D. macrophtha7ma contained 81.4% females compared with field eggs (69.6%). Based on data obtained from one single host egg, they pointed out that T. simmondsi was probably arrhenotokous. T. simmondsi took an average 9.8 days to develop from egg to adult emergence. In D. macrophtha7ma eggs, T. simmondsi took Il days to • develop at 25° C (Feijen and Schulten, 1981). We found that the average life span of an adult male and female was 25 h (range 22 - 26 h) and 35.17 h (range 25 - 50 h) respectively. Studying T. simmondsi

females at 25° C, Feijen and Schulter: (1981) reported a average l ife span of 57.6 h. T. simmondsi adults have a short life span. As a consequence, shoot fly eggs shoul d be l ess than 24 h 01 d when exposed to adul t parasitoids in a mass rearing programs. longe et al. (unpublished· data) concluded that egg parasitoids and predators are the most appropriate natural enemies of the sorghum shoot fly. Therefore, more laboratory and field studies should be focused on L simmondsi to determine its potential in controlling the sorghum shoot fly. • 187 11.6. References • Abacus Concepts Inc.- 1989. SuperANOVA, accessible general linear modeling.- Berkeley, CA., 316 p. Deeming, J. C. - 1971. Some species of Atherigona Rondani (Diptera: Muscidae) from Northern Nigeria, with special reference to those injurious to cereal crops. - Bull. Entomol. Res., 61, 133-190. Feijen, H.R., &Schulten, G.G.M. - 1981. Egg parasitoids (Hymenoptera; Trichogrammatidae) of Oiopsis macrophthalma (Diptera; Diopsidae) in Malawi. - Netherlands J. Zool., 31, 381-417. Nagarkatti, S. & Nagaraja, H. 1977. Biosystematics of Trichogrammatidae.- Annu. Rev. Entomol., 22, 157-176. Pintureau, B., & Babault, M. - 1988. Systématique des espèces africaines des genres Trichogramma Westwood et Trichogrammatoidea Girault (Hym. Trichogrammatidae). - Les colloques de l'INRA, 43, 97-120. Raina, A.K. - 1981. Movement, feeding behaviour and growth of larvae of the sorghum shoot fly, Atherigona soccata.- Insect Sci . Applic., 2, 77-81. Singh, P., Unnithan, G.C. &Del obel , A.G.L. - 1983. An artificial diet • for sorghum shoot fly larvae. - Entomol. Exp. Appl. 33, 122-124. Soto, P.E.- 1972. Mass rearing of the sorghum shoot fly and screening for ho st plant resistance under greenhouse conditions. In: Control of sorghum shoot fly (Jotwani, M.G. &Young W.R., eds.). - Oxford &IBH, New Delhi, 137-146. Takahashi, F. &Pimentel, D.- 1967. Wasp preference for black-brown and hybrid-type pupae of the house fly.- Ann. Entomol. Soc. Am., 60, 623-625. Vinson, S.B. - 1985. The behavior of parasitoids. In: Comprehensive Insect Physiology Biochemistry and Pharmacology, Vol. 9, Behaviour (Kerkut, G.A. &Gilbert, L.I. eds.).- Pergamon Press, New York, 417-469 Zongo, J.O., Vincent, C. & Stewart, R.K. - 1992. Time-sequential sampl ing of the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), in Burkina Faso. Insect Sci. Applic. (In • press) . • 188

• 11.7. TABLES

• •• •

Table 30. Percentage of A. soccata eggs parasitized by T. simmondsi and number of exit holes per egg.

Mean percentage of exit holes (n-I07)

Egg age % Paras iti sm Standard error one hole two holes

< 24 h 73.00 a• 3.10 96.26 aU 3.74·'· > 24 h 7.25 b 1. 70 98.13 a 1.87

• Mean percentages within a column with different letters were significantly different, P = 0.05. Scheffé's test. •• 2 X test, P = 0.05, *A* 2 X test could not be performed due to Cochran's restriction (i.e. expected frequency < 5).

189 • HO

Table 31. Relative size of T. simmondsi immature stages (28' C, 60-65% R.H.).

Immature stage Length (mm) n

Mean Range

Egg 0.15 0.10 - 0.20 23 Larval '; nstar First 0.22 0.20 - 0.25 13 • Second 0.35 0.30 - 0.40 11 Third 0.55 0.40 - 0.60 19 Pupa 0.45 0.40 - 0.50 21

• • 191

• 12 GENERAL DISCUSSION AND CONCLUSION

•• 192 • In February 1986, the National Sorghum-Millet-Maize Board (SOMIMA) during a meeting held at Kamboinsé, (near Ouagadougou, Burkina Faso) was concerned about the lack of research on the sorghum shoot fly. At that time, only three papers (Brenière 1972, Bonzi 1981, Bonzi and Gahukar 1983) were published on the sorghum shoot fly in Burkina Faso. Bonzi's (1981), and Bonzi and Gahukar's (1983) studies a110wed identification of 28 shoot fly species, knowledge of the proportion of two species (Atherigona soccata (14%) and A. marginifolia (36%) in a unknown sample size in 1980, and understanding of fluctuations of shoot fly adults during dry and rainy seasons. Brenière (1972) evaluated shoot fly damage in the west central region and found that sorghum seedlings were less damaged with early sowing dates. Considering the lack of research noted by SOMIMA, this work was consequently initiated to contribute in filling this gap. • Specifie conclusions have been drawn in each chapter of this thesis. In considering the whole study, the main approaches investigated may be di vi ded into four components representing an overa11 1PM program to control the sorghum shoot fly: 1) monitoring populations, 2) cultural practices, 3) natural and chemical pesticides, and 4) biological control (Fig. 5). They constitute available techniques that may be practiced to reduce shoot fly incidence under Burkina Faso conditions. Monitoring shoot fly populations is an important way to' understand the emergence pattern during the rainy season. Knowing that shoot fly populations built up rapidly after May (Bonzi 1981), that adult peak captures occur in August and September (Bonzi ·1981, Zongo et al. 1991), and that peak numbers of eggs and dead hearts occur in July and August (chapter 4, 5), sowing dates prior to June may be practiced • to avoid and reduce great losses caused by the pest. Screening dates 193 • may also be practiced in August or September to select appropriate cultivar resistant to the shoot fly. Monitoring programs could preferably cover regional levels including many countries. For example, in West Africa, monitoring shoot fly populations could cover Burkina Faso, Mali, Niger, the North of Ghana, and Togo. This could allow coordinated action to implement shoot fly control. For example, sorghum could be sown within a period of 2-3 weeks. The monitoring here investigated the relative proportion of 36 species of shoot flies over two years. This also showed that the Multi-Pher trap is effective in monitoring the shoot fly. Thirteen species were new reports in Burkina Faso, including a new species Atherigona zongoi Deeming (appendix 2) that increased the total number of shoot fly species to 41. A Time­ sequential sampling program based on egg sampling, and first establ ished for the sorghum shoot fly, is a valuable technique in • controlling this pest. This tactic allows decision to be made on wh ether or not an outbreak popul ation exi sts. Consequently, control action is made before dead heart formation. However, the field worker must keep in mind the most susceptible stage of sorghum to shoot fly attack, which ranged from 10 to 40 days after sowing in this study. Cultural practices here examined demonstrated that among the 52 local sorghum cultivars, none was resistant to shoot fly compared with the resistant cultivar IS 2123 from the USA. This indicated that work should be done on breeding sorghum against the shoot fly using the cultivar IS 2123 or other appropriate resistant cultivar as source of resistance. Although intercropping sorghum-cowpea was not conclusive in reducing shoot fly damage at all times, it gave an agronomic advantage in obtaining good yields of both crops. (chapter 5). Intercropping • sorghum-cowpea increased the number of Neotrichoporoides nyemitawus, a 194 • shoot fly larval parasitoid, and five species of spider (Araneus sp. Meioneta prosectes, Misumenops sp., Neoscona sp., and Steatcda badia). Therefore, this practice could be done to augment or conserve these natural enemies (chapters 8, 9). The cultural practices are the least expensive tactics for farmers based on their present knowledge and agricultural income. However, they require careful timing and unified action by farmers. In chapter 5, l found that shoot fly damage was lower (6.47% and 10.20% ~espectively in 1988 and 1989) wh en sorghum was sown on June 20 than sowing dates after June 20. Therefore, l recommended that sorghum be sown prior to June 20 in an unified action to avoid great losses caused by the shoot fly. My recommendation could be more effective if farmers from the same locality in cooperation with extension service applied it. It is well known that staggering sowing dates of sorghum during the • cropping season favors shoot fly population outbreaks (Nwange 1988, ICRISAT 1983). This supports the previous recommendation that sorghum be sown at the same time for the same locality or when possible on a regional basis. Hill (1989) pointed out that cultural practices are valuable"control tactics but need implementation by governmental poliçy and legislation, more research, training and publ ic education. In Burkina Faso, the government could take measures favoring the application of the classic system Research-Demonstration-Training. This system would provide a secure knowledge base and access to appropriate technologies. For example, broadcasting the results here found on a large scale through the extension service could improve the transfer of shoot fly technology to the farmer level. The cultural practices discussed in this thesis could be • particularly useful when integrated with monitoring shoot fly 195 • popul ations, sequenti al sampling, and the use of natural insect ici de such as neem seed kernel extracts found to be effective in reducing egg numbers and dead heart incidence (chapter 7). As stated in chapter 7, neem tree grows well in all parts of Burkina Faso and thus could be an appropriate component of an IPM program for farmers who have generally low sorghum income and capital. For instance, 1 kg of neem would cost 50 F CFA comparing with 1 kg of carbofuran, which currently costs 1600 F CFA. Cultural practices may also be integrated with the use of carbofuran, an effective chemical pesticide against the shoot fly. However, this integration should be done wh en delayed planting entails outbreak populations of eggs on a large scale during the cropping season. The carbofuran treatment could be applied particularly in larger scale farming where intensification of agriculture is better than in smallholder farming. • Biological control, the fourth component investigated in this study, offers a potential for implementing a sorghum shoot fly control program. Important biocontrol agents such as egg natural enemies (Fusarium sp. , Corynebacterium sp. , Tapinona sp. , and Trichogrammatoidea simmondsi), larval parasitoids (Bracon sp., and Hockeria sp.) were first recorded (chapter B). Other natural enemies namely Neotrichoporoides nyemitawus, a larval parasitoid, and various spider groups were also recorded (chapters 8, 9). These natural enemies add to the existing wide range of shoot fly natural enemies. Although these findings could not be directly applied to the farmer level at the present time, they constitute an important step forward in the implementation of biological control of the shoot fly. Potential biocontrol agents such as T. simmondsi (7 to 12% of parasistism) and N. • nyemitawus (6 to 17% of parasistism) were identified with subsequent 196 • studies on their biology. The studies revealed for the first time that these parasitoids could be easily reared with low inputs (chapters 10, 11). Important quest ions such as wh i ch instar of the shoot fl y i s susceptible, and how long are the parasitic stages have been answered (chapters 10, Il). More research should be pursued in the laboratory as well as in field conditions to improve possible timing of releasing parasitoids, and to determine the potential of microbiocontrol agents. In summary, the sorghum shoot fly control program shoul d be focused on eggs before dead heart formation. Several tactics could be transferred to the farmer level with an emphasis on cultural practices, the use of neem seed extracts, and time-sequenti al sampl ing. Thi s transfer needs multidiscipl inary intervention in which researchers, extension service personnel and politicians should play an important • role.

• 197 •

Figure 5. Approaches to sorghum shoot fly IPM investigated in this thesis. •

• 1. Monitoring populations . 2. Cultural Practlces

-Tl8pplng adult. (ch.pl.r3) -Sowlng dalaa (chaplar 5)

-Inlarcropplng aorghum·cowpea (chaplar 5) - ""'Iu.nllal aempllng DI agg. (chapl.r 4) - Ra.lalanl cuillvara (chaplar 6)

Alhsr/gona sacea'a (Dlptera:Muscldae) (Sorghum Shoot Ay)

3. Natural and Chemlcal Pesticides 4. Blologlcal Control

- Trlchogfllmm.,old...Jrnmonda/(chaplara 8,11) -Az.dlf8Chl.lndlca (nHm) axtl8c1a (cheplar 7) - Carbolul8n (cheplar 7) • NlOlrlchoporolda. nYMn/l.awu. (chapl.ra 8, la) - Spldara and mlcrobloconlrolaganl. (chaplara 8, 9)

• • • • 198

• 13 REFERENCES

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Sorghum insect problems in Brazil, pp. 97-101. In International Crops Research Institute for the Semi-Arid Tropies. Proeeedings of the International Sorghum Entomology Workshop, 15­ 21 July 1984, Texas A &MUniversity, College Station, TX, USA, Patancheru, India. Vinson, S.B. 1985. The behavior of parasitoids, pp. 417-469. In Kerkut, G.A. and Gilbert, L.I. (eds.). Comprehensive Insect Physiology Biochemistry and Pharmaeology. Vol. 9, Behaviour. Pergamon Press, New York, 417-469. Wald, A. 1947. Sequential analysis. Dover Publications, iNC. New York. 212 p. • Waters, W.E. 1955. Sequential sampling in forest insect surveys. For. Sei. 1: 68-79. Yathom, S. 1967. Effects of irrigation on the effieieney of soil treatments with granul ar, sjiternie insectieides against the sorghum shoot fly, Atherigona varia Rond. in Israel. Israel J. Entomol. 2: 171-178. Young, W.R. 1981. Fifty-five years of researeh on the sorghum shoot fly. Inseet Sei. Applie 2: 3-9. Young, W.R. and Teetes, G.L. 1977. Sorghum Entomology. Annu. Rev. Entomol. 22: 193-218. Young, O.P. and Lockley, T.C. 1985. The striped lynx spider, Oxyopes saltieus (Araneae: Oxyopidae) in agroeeosystems. Entomophaga • 30: 329-346. 226 • longo, J.O. 1987. Entomologie du sorgho et mil, pp. 1-3. In Rapport de synthèse de la campagne 1986. M.A.E., D.A. Service Protection des Végétaux, Laboratoire de Recherches Bobo-Dioulasso, Burkina Faso. longo, J.O., Vincent, C. and Stewart, R.K. 1991. Monitoring adult sorghum shoot fly Atherigona soccata Rondani (Diptera: Muscidae), and related species in Burkina Faso. Trop. Pest Manag. 37: 231­ 235. longo, J.O., Vincent, C. and Stewart, R.K. 1992. Time-sequential sampl ing of the sorghum shoot fly, Atherigona soecata Rondani (Diptera: Muscidae), in Burkina Faso. I.'7seet Sei. App7ie. (In press) . •

•• 227 Appendix 1- • Manuscripts and Presentations Based on this Thesis. Scientific publications 1) Zongo, J.O., C. Vincent, R.K. Stewart 1991. Monitoring Sorghum Shoot Fly Atherigona soccata Rondani (Diptera: Muscidae) and Related Species in Burkina Faso. Tropical Pest Management 37 (3), 231-235. 2) Zongo, J.O., C. Vincent, R.K. Stewart 1992. Time-sequential Sampling of Sorghum Shoot Fly Atherigona soccata Rondani (Diptera: Muscidae), in Burkina Faso. Insect Science and its Application (In press). 3) Zongo, J.O., C. Vincent, R.K. Stewart 1992. Effects of Neem Seed Kernel Extracts on Egg and Larval Survival of the Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae). Journal of • Applied Entomology (In press). 4) Zongo, J.O., C. Vincent, R.K. Stewart 1992. Effects of Intercropping Sorghum-Cowpea on Natural Enemies of the Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae) in Burkina Faso. Biological Agriculture &Horticulture (In press). Papers submitted 1) Zongo, J.O., R.K. Stewart, C. Vincent. Biology of Trichogrammatoidea simmondsi Nagaraja (Hymenoptera: Trichogrammatidae) on Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae) eggs. Entomophaga, July 1992. 2) Zongo, J.O., R.K. Stewart, C. Vincent. Parasitism of Sorghum Shoot Fly Larvae, Atherigona soccata Rondani (Diptera: Muscidae) by Neotrichoporoides nyemitawus Rohwer (Hymenoptera: Eulophidae). • Insect Science and its Application, July 1992. 228 • Papers to be submitted 1) Zongo, J.O., R.K. Stewart, C. Vincent. Spider Fauna in Pure Sorghum and Intercropped Sorghum-Cowpea in Burkina Faso. Journal of Applied Entomology. 2) Zongo, J.O., R.K. Stewart, C. Vincent. Influence of Cultural Practices on Sorghum Yields and Incidence of Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae), in Burkina Faso. Sahel Phytoprotection. 3) Zongo, J.O., C. Vincent, R.K. Stewart. Screening of Local Cultivars for Resistance to Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae), in Burkina Faso. Sahel Phytoprotection. Miscellaneous papers 1) Zongo, J.O., C. Vincent et R.K. Stewart 1989. Etudes sur la mouche des pousses du sorgho grain Atherigona soccata Rondani (Diptera: • Muscidae) dans l'Ouest Burkina, pp. 48-62. In Rapport de synthèse de la campagne 1988-1989. Min. Agric. El.evage., Dir. Agric., Service Protection des Végétaux, Laboratoire de Recherches Bobo-Dioulasso, Burkina Faso. 2) Zongo, J.O., C. Vincent et R.K. Stewart 1990. Etudes sur la mouche des pousses du sorgho grain Atherigona soccata Rondani (Diptera: Muscidae) dans l'Ouest Burkina: résultats sommaires de 1989. In Rapport de synthèse de la campagne 1988-1989. Min. Agric. Elevage., Dir. Agric., Service Protection des Végétaux, Laboratoire de Recherches Bobo-Dioulasso, Burkina Faso. 3) Zongo, J.O., C. Vincent et R.K. Stewart 1991. Dépistage et abondance relative des Muscidés (Atherigona spp. Rondani) associées au sorgho grain cultivé au Burkina Faso. SAHEL PV • . INFO Bulletin d'Information en Protection des Végétaux de 229 • l'UCTR/PV (Bamako, Mali), 37: 11-16. Oral presentations 1) longo, J.O., C. Vincent et R.K. Stewart 1990. Efficacité de quatre types de pièges pour la capture d'Atherigona soccata Rondani (Diptère: Muscidae) et effets de quelques pratiques culturales sur ses dégâts au Burkina Faso. Deuxième Séminaire sur la lutte intégrée contre les ennemis des cultures vivrières dans le Sahel tenue à Bamako (Mali) du 4 au 9 Janvier 1990. 2) longo, J.O., C. Vincent, R.K. Stewart 1991. Sequential Samplin9 of Sorghum Shoot Fly Atherigona soccata Rondani (Diptera: Muscidae), in Burkina Faso. Major Symposium on Exotic Pests In Africa; their Prevention and Control. 9th Meeting and Scientific Conference of the African Association of Insect Scientists 23rd­ 27th September 1991, Legon, Accra, Ghana. • Poster presentations 1) longo, J.O., C. Vincent et R.K. Stewart 1990. Dépistage de la mouche des pousses du sorgho, Atherigona soccata Rondani (Diptera: Muscidae) au Burkina Faso. Annual meeting, Entomological Society of Canada, Banff, Alberta, 7-10 octobre 1990. 2) longo, J.O., C. Vincent, R.K. Stewart 1992. Effects of Neem Seed Kernel Extracts on Egg and Larval Survival of the Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae). XIX International Congress of Entomology, June 28 - July 4, 1992, Beijing, China. • 230 Appendix z. • Atherigona zongoi: trifoliate process and hypopygial prominence; morphological characters used for identification'•

• a)

l 2 Aih09ona. ~n.3.0i sp.n.

A): trifoliate process; l ~entral Vi2W, Z profile. B): hypopygial prominence; l apical view, Z profile.

• 1 Drawing by J.C. Deeming, National Museum of Wales, Cardiff, U.K . 231 •

Appendix 3. Sorghum shoot fly, Atherigona soccata: adult, immature stages and damage. •

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Adult fly •

Egg on a piece of sorghum leaf 232

Larva: third instar •

Damaged pl~nt~and tillers 233 •

Appendix 4.

Copyright waiver given by Tropical Pest Management rel ated to the publ ication of "Monitoring Adult Sorghum Shoot Fly, Atherigona soccata • Rondani (Diptera: Muscidae), and Related Species In Burkina Faso" by Zongo et al. (1991).

• Taylor & Francis Ltd Inlt"I"J'UZlional SciOflific and Educalional Publishm. London and W'oshmglon, De E"ablish

19 June 1992

Joanny 0 Zongo Macdonald College of McGil! University Department of Entomology 21 111 Lakeshore St-Anne-de-Bellevue Quebec Canada H9X 1CO

DearJoanny Tropical Pest Management Peter Haskell has passed your letter of 13 May to us, in which you ask us to waive copyright on your manuscript which appeared in our journal. so !hat yeu may include it in your thesls. This is to confirm !hat we are happy to do so on this occasion. Yours sincerely • (j M(};D~ Geraldine Crowe Permissions

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