75-79 sdi/2/19 20/9/01 3:09 pm Page 61

Use of the Sterile Technique Against Key Insect Pests

JORGE HENDRICHS, Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, Austria

killing of fish, birds, mammals and other wildlife. A B S T R A C T In view of the above there is an urgent need to develop and implement more enviro n m e n t - f r i e n d l y methods to manage insect pests, such as the Sterile Insect he world's population is increasing by ca. 80 million Technique (SIT), that are biologically-based and there- humans per year and in developing countries fo r e are more sustainable. Losses in production and trade Tthe total production of food must be doubled in crops and livestock products due to major insect pests, coupled with rising concerns about food safety and within the next thirty years. Expansion of arable land quality and biodiversity, have led to demands at national can only play a minor role to further growth in food and international levels for the development and intro- p roduction, but attaining substantial increases in duction of area-wide and biological approaches for average yields will become increasingly difficult, and the integrated management of major insect pests. Many countries have benefited from insect intervention will have to focus on using re s o u rces more eff i c i e n t l y. pr ogrammes which, through the integrated use of SIT, Pre - h a r vest losses in developing countries are estimated incorporate these concepts. Apart from reducing crop at about 40%, while post-harvest losses add a furt h e r losses and use, a major aim of appropriate pest insect intervention is to facilitate international trade of 10-20%, much of which is due to insect pests. There agricultural commodities by providing Member States could hardly be a less efficient use of re s o u rces than with better options for addressing technical barriers to to invest water, fert i l i s e r, seeds, land, time, eff o rt and trade and other sanitary and phytosanitary issues br ought before the WTO. Area-wide use of SIT has been money in producing food, only to have it partially or totally shown successfully to establish pest free areas, areas of d e s t royed by or other pests. Consequently, an low pest prevalence through a systems approach, and i m p o rtant strategic component of raising pro d u c t i v i t y can be used to a greater degree in the future to achieve and assuring global food security will increasingly be more effective management of insect pests. investment in improved insect pest management, one method of which is the Sterile Insect Technique (SIT). CURRENT STATUS AND ACHIEVEMENTS The principle of SIT and its advantages The Sterile Insect Technique (SIT) involves mass pr oduction of the target insect pest species, sterilisation and releasing into the field on a sustained basis and in O V E RVIEW - PROBLEMS AND RAT I O N A L E su f ficient numbers to achieve appropriate overfl o o d i n g The World Bank predicts an increase in insect pests, ratios. Sterile males find and mate with fertile females, including disease vectors, due to increased intern a- t r a n s f e rring infertile sperm. There are no re s u l t i n g tional trade and global climatic change. Examples of these viable offspring, resulting in a reduction in the natural tr ends are already apparent in the livestock sector, as tsetse pest population. flies and Old World Screw w o r m (OWS) are advancing Unlike non-selective insecticide-based control, the into previously uninfested agricultural areas. SIT and other less known genetic pest control methods The present value and importance of conventional ar e environmentally friendly. The induced sterility is direc t e d synthetic insecticides to pest control cannot be questioned. exclusively at the target species and, contrary to other World pesticide consumption is growing at ca. 5% a year, biological control methods, no adverse impacts on but there are major resistance problems, as well as n o n - t a rget organisms have been re p o rted. It can be in c r easing public awareness of the high toxicity, res i d u e s integrated with other conventional and biological in food, contamination of water and the environment, methods, such as parasitoids, predators and insect and concerns of human health effects. The conse- pathogens (biopesticides). This integration enables the quences of wide-spread application of broa d - s p e c t ru m application of totally biological systems for managing insecticides have been outbreaks of secondary pests that some of the world's most important insect pests. result in additional crop losses and insecticide use SIT also exhibits increased efficiency with decrea s i n g because of the inadvertent destruction of natural t a rget population density. As a result it is the only enemies as well as the impact on beneficial non-target en v i r onmentally friendly technology available that can insects such as honey bees and other pollinators, and the eradicate insect pests if applied consistently on an area -

S U S TA I N A B L E D E V E L O P M E N T IN T E R N AT I O N A L 75 75-79 sdi/2/19 20/9/01 3:09 pm Page 62

an internationally funded programme was initiated. Sterile pupae were transported from Mexico to Libya and released by air as adult flies over a treatment area of 40,000 km2. Between 1990 and 1992, 1,300 million sterile flies were released and 40 million animal inspec- tions were carried out, resulting in the eradication of NWS. The last case of screwworm was reported in 1991.

Fruit flies F ruit flies seriously interf e re with the intern a t i o n a l marketing of fruit and vegetable commodities, and thus are a major impediment to economic develop- ment. Few insects have a greater impact on world trade in agricultural produce than fruit flies, and SIT is seen as a major tool within a systems approach to cr eate internationally recognised fly free or low prev a - lence areas to overcome these trade barriers. Fruit flies also cause devastating direct losses requiring inten- sive insecticide treatments to produce worm- f r ee frui t . The resulting damage to non-target beneficial orga n i s m s , d i s ruption of biologically based controls of other Figure 1 wide basis. This area-wide population management orc h a r d pests, and general contamination of the environ - Worldwide production capacity of ap p r oach is central to the application of SIT. It involves ment, are the other major forces driving the need for more sterile fruit flies action against the total population of the pest over a period en v i r onment-friendly methods such as SIT to control frui t of generations, requiring much less input and achieving flies. much greater suppression than a higher level of suppres - The Mediterranean fruit fly (medfly), C e r a t i t i s sion on most, but not all, of the population in each capitata, a notorious quarantine pest because of the generation. ex t r emely wide range of host it attacks, has been one of the main targets for SIT. The first large SIT prog r a m m e PRACTICAL APPLICATION OF SIT IN THE PA S T against medfly was initiated in Mexico in 1977, with the co n s t r uction of a 500 million sterile fly mass rearing facility. Screwworm flies The aim of the programme was to prevent the spread The first and probably most widely known applica- of medfly, which had become established in Central tion of the SIT against a major insect pest is the America, into Mexico and the USA, which threatened successful screw w o r m programme that eradicated this Mexico's multi-million fruit and vegetable export trade pest from large areas of North and Central America. The with the USA. The programme succeeded in 1982 in eradi- New World Scre w w o rm (NWS), C o c h l i o m y i a cating medfly from areas it had already infested in hominivorax, a -causing fly in warm-blooded so u t h e r n Mexico and has since then maintained a sterile animals, including humans, is a pest of major economic fly barrier from southern Belize through Guatemala to i m p o rtance in agricultural systems with extensive so u t h e r n Mexico to assure the fly-free status of Mexico, livestock production or with increasing labour costs. USA and half of Guatemala. After a successful SIT pilot eradication in Curazao This was the starting point for similar medfly control in 1954, a successful eradication programme was or eradication programmes in various other parts of the c a rried out in Florida in the late 1950s. This was world such as , Argentina and . Repeated followed by total eradication of NWS from the United medfly introductions into California and Florida, threa t - States between 1966 and 1982. A production plant with ening the exports of a multi-billion fruit industry, have a capacity to produce 600 million sterile flies per week re q u i red re c u rrent emergency eradication actions, was opened in southern Mexico in 1976. Eradication in costing annually millions of US dollars. In view of the Mexico moved prog r essively southward to the Isthmus public opposition to aerial bait-spraying, often over of Tehuantepec by 1984, and all of Mexico was declared urban areas, and the failure to eradicate these outbrea k s free of NWS in 1991. Since then eradication has been with insecticides, authorities successfully embarked achieved in Belize and Guatemala in1994, El Salvador on the area-wide use of SIT over the whole Los Angeles in 1995, Honduras in 1996, and recently Nicaragua (1999). Basin starting in 1994, involving the aerial release of over Sterile fly releases are presently continuing over Costa 300 million sterile flies per week. The SIT strategy Rica, which is already largely NWS-free, and over was so successful politically and environmentally, but , where a new mass rearing facility is foreseen also from the economic point of view (costing on to maintain a permanent barrier of sterile flies in the Darien average less than half compared to the re c u rre n t Gap between the Panama Canal and the border with em e r gency programmes), that after successful eradication Colombia. in 1996, area-wide aerial releases were continued on a The accidental introduction of NWS into Libya in 1988 pe r manent basis over high risk areas in the Los Angeles represented a major emergency in view of the threat it basin. This preventive or prophylactic approach has stopped rep r esented to wildlife and livestock not only for Libya, any major outbreaks of medfly. but for the entire North Africa and Mediterr a n e a n Recent development by IAEA of male-only strains regions. It was the first time that this destructive insect ( F i g u re 1), opening the possibility of using SIT for became established outside its natural range in the routine medfly control rather than eradication, has Americas, and if left uncontrolled it would inevitably sprea d resulted in SIT programmes in various stages of devel- to neighbouring countries and eventually into the Near opment in Madeira, Israel, Jordan and Palestine, as East, Mediterranean Europe and possibly even Sub-Saharan 2 well as South Africa, and feasibility studies in various Africa. By 1990 the infestation had spread to 25,000 km other Mediterranean countries. This considerable containing some 2 million livestock. A decision was taken activity indicates an increasing interest in the region in to try to eradicate the outbreak using sterile insects and

76 S U S TA I N A B L E D E V E L O P M E N T I N T E R N AT I O N A L 75-79 sdi/2/19 20/9/01 3:09 pm Page 63

substituting medfly control based on insecticide sprays with environment – friendly medfly control based on SIT. The economic feasibility of this approach has been confirmed by a number of benefit-cost analyses. For medfly and other fruit flies, the current world- wide weekly production capacity of sterile flies has now reached several billion sterile flies. B a c t rocera and A n a s t repha a re also devastating fr uit fly pests of economic and quarantine importa n c e . Gr eat advances have been made in developing sterile insect technology for some of these species. The programme in southern Japan culminated in the mid- 1990s in the eradication of this species from all islands of the Okinawa and other archipelagos. In , SIT was successfully applied to eradicate the Queensland frui t - fly from Wes t e r n Australia, and preventive SIT rel e a s e s are being used in Southern Australia to protect fruit gr owing areas from the seasonal movement of the pest into commercial areas. In the Philippines the sterile insect technology has been adapted to B. philippinensis and a pilot programme has been in pro g ress in mango- producing Guimaras Island. integrated use of SIT to eradicate tsetse in Zanzibar, initi- Figure 2 Th e r e has been an operational SIT programme in the ated in 1994 against Glossina austeni. Intensive Worldwide facilities for mass pro- USA as a quarantine against the Mexican fruit fly along monitoring over Zanzibar during the three years duction of sterile insects the border with Mexico since 1964, and SIT is being used following eradication shows no tsetse have been found. in Florida against A. suspensa, in combination with Disease monitoring also has shown that cattle are free parasitoids and other methods, to establish fly – free zones of trypanosomes. in areas of citrus production. In north e r n Mexico a large SIT programme against various An a s t r epha species, funded Lepidoptera by the fruit industry and federal and state governm e n t s Lepidoptera (moths) are amongst the most damaging has been in prog r ess since the early 1990s with the objec- pests of food and fibre crops, forests and stored prod u c t s tive of developing fly – free areas. th r oughout the world. Some of these pests are also major candidates for inherited sterility programmes. Curren t l y , most of these species are controlled largely by applications Tsetse flies have a devastating effect on humans and of insecticides, but in many instances this practice has livestock production in 38 countries south of the Sahara induced insecticide resistance and secondary pests covering ca. 7-11 million km2. Trypanosomiasis, caused outbreaks. by tsetse, rep r esents a key impediment to the establishment The cotton pink bollworm, Pectinophora gossypiella, of sustainable agricultural systems in many areas of grea t is a serious cotton pest in many parts of the world. A agricultural potential. People in Sub-Saharan Africa get pr ogramme against this pest in California has since 1968 a third or less than a third as many calories and half as been successfully integrating aerial sterile moth rel e a s e s much protein from animal products as people in devel- and various cultural and other controls. Its objective has oped countries. Also, no healthy cattle are available in been to prevent this migrating pest from becoming tsetse infested areas for ploughing and as draught established in the San Joaquin Val l e y , to protect the cotton animals, thus effectively preventing economic development grown there. In order to address moth migration at its in many countries south of the Sahara. origin in other cotton growing areas, the Phoenix, Sufficient food can only be provided if existing but Arizona, mass rearing facility was enlarged in 1994 and u n p roductive crop and livestock systems continue the programme was extended to the Imperial Valley and expanding into wildlife areas or if more intensified in 1998 to other valleys to eradicate the established pest and better integrated systems are introduced into in these areas. Plans exist to include all cotton areas in existing areas. The latter is necessary for pres e r ving natural other southwestern states, Arizona and New Mexico in res o u r ces but will req u i r e, amongst others, the introd u c t i o n the USA and Baja California Norte and Sonora in of improved livestock breeds which can only be Mexico. maintained profitably if area-wide approaches are , Cydia pomonella, is a key pest of apples applied to address the tsetse/trypanosomiasis prob l e m , and pears in many temperate regions of the world, and preferably if tsetse flies are eradicated thro u g h being the target of intensive insecticide sprays. An SIT integrated interventions. programme against this pest was initiated in British To date, no major break-through has been made in Columbia, Canada, in the early 1990s. With funding from removing or sustainably controlling the threat of tsetse the federal and provincial governments, a mass rea r i n g and trypanosomiasis. Present disease control, mainly based facility was built with a capacity of producing 15 on trypanocides, insecticide impregnated targets, or million moths per week. After four years of opera- even habitat destruction and game elimination, is unsat- tions, the programme has been successful in control l i n g is f a c t o r y in the long term due to high cost, resistance and the pest with growers essentially reporting no damage en v i r onmental concerns. The transboundary nature of and most not having to spray against codling moth, allowing the disease re q u i res that eventually an are a - w i d e the production of organic fruit. integrated approach must be designed for entire sub-reg i o n s to break the vicious cycle of human/livestock diseases Current SIT fly factories and economic disadvantage. The numbers of existing sterile insect mass prod u c t i o n Recent brea k t h r oughs in mass rearing and aerial rel e a s e facilities for the major insect groups for which SIT is being technology have culminated in the first area-wide and applied is shown in Figure 2, where it can be seen that

S U S TA I N A B L E D E V E L O P M E N T IN T E R N AT I O N A L 77 75-79 sdi/2/19 20/9/01 3:09 pm Page 64

5% of the total cattle on the island. The development of a new synthetic insecticide currently takes an average of 10 years to bring a new product to market at an average cost of ca. US$ 120 million. Development of an SIT package for a specific key pest, involving mass rearing and aerial release, as well as field monitoring and suppression system, req u i re s much less funding. The cost of insecticide develop- ment will probably continue to rise because of increa s i n g l y stringent standards imposed by re g u l a t o ry agencies, and will be reflected in more expensive newer insecti- cides, resulting increasingly in more competitive costs for biologically-based methods such as SIT. In general, the economic feasibility of non-chemical pest control tools, including biologically-based methods such as SIT, will become increasingly apparent, with more realistic accounting of the negative enviro n m e n t a l effects of synthetic pesticide applications, and further im p r ovement in the cost-effectiveness of these methods as a result of continuing investment in applied R & D. Figure 3 medfly and other fruit fly SIT are the most widely Sterile insect mass production adopted. facilities The worldwide distribution of these facilities, shown FUTURE TRENDS IN THE USE OF SIT in Figure 3, indicates that 60% of these SIT facilities are The vast majority of insect species are beneficial to man. located in the We s t e rn Hemisphere, where applica- Of the estimated several million insect species, only a tion of SIT technology is most advanced. few thousand are pests of man, livestock, food or fibre crops, or stored products. Out of these insect pests, a ECONOMIC AND ENVIRONMENTAL BENEFITS majority are occasional, surpassing the economic t h reshold level only occasionally when favoured by Economic analyses have shown that SIT applied for control special weather conditions, or secondary pests, when the or for eradication as part of an integrated approach is action of their enemies is disrupted by human interve n t i o n . competitive with conventional methods when consid- For these pest species the conventional IPM approach er ed over longer time frames. Particularly in the case of has been successful. eradication, the impact of control or eradication effo rt s For the so-called key insect pests, however, which using this technique are concrete and directly measur- continuously cause damage above economic thres h o l d able. Even when excluding the large enviro n m e n t a l levels, this IPM approach has not been so effective in benefits that have resulted from the implementation of view of increasing pesticide consumption. Considering SIT control or eradication programmes, SIT has had major the importance of these key pests and their potential for economic impacts. economic and environmental impact, these are the In the case of the New World Screw w o r m fly, the invest- species that are the targets for area-wide approaches ment of almost US$ 1000 million between 1957 and 2000 including in some cases the use of Sterile Insect resulted in the eradication of the pest from the north e r n Technique (SIT). Among key pests, obviously only half of the whole We s t e rn Hemisphere. The annual those species should be considered as targets for which d i rect producer benefits in the previously aff e c t e d there are no promising alternative technologies under countries is estimated at US$ 1165 million and econo- development. mists estimate that the multiplier effect on the economy The applicability of area-wide techniques will be stron g l y and wildlife health component is at least three times this encouraged by global economic trends. Farmers and amount. gr owers are being forced towards further rationalising For fruit flies, eradication of medfly from Mexico and and integrating of activities, as well as associating into maintaining the country free of this pest at an annual la r ge production and trading units, whose survival will cost of US$ 8 million, has protected fruit and vegetable often depend on overcoming pest-related non-tariff e x p o rt markets of close to US$ 1 billion/year. The ba r riers to the free trade of their agricultural prod u c t s . eradication of the medfly Mediterranean fruit fly from Chile, is estimated to eventually result in opened Screwworm flies markets for fruit exports of up to US$ 500 million per In the short term, support to SIT eradication projects ye a r . Allowing the establishment of medfly in Californi a is focusing on the Caribbean islands where the pest is would result in the loss of $US 1 billion a year and res u l t still endemic, making it a possible source of re- i n f e s t a t i o n . in a drastic increase of insecticide use. In Israel, rec e n t In 1998, a NWS eradication project was initiated in eff o r ts to use SIT for control, rather than eradication of Jamaica, where aerial sterile fly releases are currently under m e d f l y, have already resulted in annual exports of way throughout the island. Eradication of NWS is peppers and tomatoes to lucrative markets in the United expected by the year 2001. Prep a r a t o r y activities are also States valued at US$ 5 million. al r eady in prog r ess to initiate NWS eradication proj e c t s , The elimination of the trypanosomiasis problem on first in Cuba, and in the medium term in Hispaniola Zanzibar is resulting in significant gains in the livestock (Dominican Republic and Haiti). In the long term , sector with the introduction of more productive cattle NWS eradication can be envisioned for South America, breeds. Whereas in 1985/86 only every third farming wh e r e there is interest in several countries for such a large household had cattle, in 1999 four out of five farmers programme. ar e integrating farming and cattle management. Alrea d y The Old World Scre w w o rm (OWS), C h ry s o m y a more than one third of the total milk production on be z z i a n a , is another obligate parasite of warm- b l o o d e d Zanzibar originates from improved cattle bre e d s , animals that is confined to tropical and sub-tropical reg i o n s although these improved breeds only represent about of the Old World, where it makes large scale beef

78 SU S TA I N A B L E DE V E L O P M E N T IN T E R N AT I O N A L 75-79 sdi/2/19 20/9/01 3:09 pm Page 65

production uneconomic. Australia is free of OWS but Lepidoptera establishment of this pest is a permanent threat to A number of other developments are in progress for Australia's large livestock industry and scientists there applying SIT for control purposes against moth pests in have successfully adapted the existing NWS technology various parts of the world but these are mostly exper- for OWS. There is demand for this technology in imental and will req u i r e considerable additional res e a rc h islands of Southeast Asia and particularly in the Middle or upscaling to become operational. These include East, where OWS has spread over the last decade codling moth in South America and South Africa, throughout the Persian Gulf region. It is now causing gypsy moth in the USA, diamondback moth in Mauritius, la r ge outbreaks in Iraq, and from there it is threa t e n i n g date moth in Tunisia, cotton bollworms in China and to invade the Near East and Mediterranean regions. Pakistan and a number of other countries, sugarcane borer Feasibility studies are in prog r ess for the eradication of in Cuba, peach borer in Bulgaria, etc. OWS from selected regions in the Middle East and South East Asia. C O N C L U S I O N Fruit flies Insect pest control is becoming more difficult. The Th e r e is much interest in applying SIT against other frui t intensification of cropping, reduced crop rotations and flies and in other regions. The European Union, which in c r eased monocultures will create further biological imbal- until recently was not interested in supporting the ances of the agricultural environment. Future pest application of the SIT for medfly control or eradication, c o n t rol will have to be conducted without furt h e r is increasingly realising the obvious advantages of the impairing biological diversity and degrading the environ - technique in terms of economics, environment and ment, and will have to be accomplished to a significant consumer protection. As a result the EU re c e n t l y extent with less reliance on . The environ m e n t requested support from IAEA and FAO for an SIT will be further disrupted as a result of the continuing expan- initiative and is currently encouraging the establishment sion of world-wide travel, tourism, as well as trade in of fruit fly SIT control rather than eradication prog r a m m e s agricultural products, increasing the introductions of among its members in Southern Europe. Curre n t l y noxious plants, insects and other pest organisms from th e r e is also much interest in various Central American one area to another. Furth e rm o r e, insecticide use, as well and South American countries for regional effo r ts to expand as insect damage levels considered acceptable in the past, a reas under SIT and for developing SIT technology ar e now no longer acceptable, and millions of people and for various other Anastrepha fruit flies. animals suffer from arthropod-borne diseases that are increasing in importance due to resistance. Tsetse flies In view of the above, there is no doubt that the demand The recent success in Zanzibar has led to its consider- for SIT and related biologically-based insect pest control ation for areas of mainland Africa. Eradication of tsetse techniques that can address transboundary pest prob l e m s in areas with high land-use pres s u r e is the favoured option will continue to increase. The close collaboration of IAEA for governments, seeing that it creates the prere q u i s i t e and FAO over the past four decades is succeeding in devel- for introducing intensified livestock/agricultural practices, oping and implementing SIT as an effective tool within th e r eby limiting the need for expanding lower-p ro d u c - an integrated approach to pest management. tive land-use systems into wildlife areas. Thus considerable e ff o rts are under way to upgrade tsetse SIT for integra- tion into intervention campaigns in selected areas of A B O U T T H E A U T H O R mainland Africa. This requires that methods be devel- JORGE PEDRO HENDRICHS is the Head of Insect and Pest oped which produce at least 500,000 sterile males per week for release over areas of 5,000 – 10,000 km2. C o n t rol Section, Joint FAO/IAEA Division of Nuclear A recent DFID funded economic assessment of the Techniques in Food and Agriculture, Vienna, Austria. He is an ts e t s e / t r ypanosomiasis problem concludes that invest- elected Member to The Council of the International Congresses ments into larger scale eradication programmes will res u l t of Entomology, a Member of Science Advisory Panel for Fruit Fly in 2.6-fold benefits of investments over a 20 year period, accumulating to more than fivefold the invest- Control, California Department of Food and Agriculture, and a ments in subsequent years. In this context tsetse SIT is Member of International Advisory Panel for Medfly Control, receiving increasing attention and support, as it is United States Department of Agriculture. He has highly environmentally friendly and, in many situa- tions, is an ideal complementary tool to conventional tsetse Consultantships to the governments of Argentina, Chile, Japan, intervention methods. Spain, Philippines, Portugal, South Africa and Thailand. The Ethiopian government has embarked since 1996 on preparatory activities for an SIT programme for eradicating tsetse flies from 25,000 km2 of the I F Y O U H AV E A N Y E N Q U I R I E S R E G A R D I N G T H E So u t h e r n Rift Val l e y . The first phase consisting of base- C O N T E N T O F T H I S A RT I C L E, P L E A S E C O N TA C T: line data collection will soon be completed, and so far Dr. Jorge Hendrichs G. pallidipes was identified as the only tsetse species in the core area of the surveyed Rift Val l e y . Effo r ts are also Head, Insect & Pest Control Section being pursued to establish a mass reared strain of G. Joint FAO/IAEA Division of Nuclear Techniques in pallidipes originating from the area, and construction Food and Agriculture of a mass rearing facility with a capacity to produce 1 P.O. Box 100 million sterile males is scheduled to be initiated in A-1400 Vienna 2000. The Tanzanian government has identified two other sites in Tanzania where similar projects would have an Austria equally good chance of success. Tsetse SIT eradication Tel: +43 1 2600 21628 pr ojects are currently also being considered or are in prep a - Fax: +43 1 26007 ration in selected areas in Kenya, Mali, South Africa and E-mail: [email protected] Botswana.

S U S TA I N A B L E D E V E L O P M E N T IN T E R N AT I O N A L 79 75-79 sdi/2/19 20/9/01 3:09 pm Page 66

66 S U S TA I N A B L E D E V E L O P M E N T I N T E R N AT I O N A L