Vol.12_No.2 - Pesticide Alternatives Lab - Michigan State University

Spring 2003 Resistant Pest Management Newsletter Vol. 12, No.2Plapp, F. W., G. M. McWhorter, and W. H. Vance. 1987. Monitoring forpyrethroid resistance in the tobacco budworm in Texas-1986, pp.324-326. In Proceedings 1987 Beltwide Cotton Conf., NationalCotton Council, Memphis, TN.Plapp, F. W., Jr., J. A Jackman, C. Campanhola, R. E. Frisbie, J. B.Graves, R. G. Luttrell, W. F. Kitten, and M. Wall. 1990. Monitoringand management of pyrethroid resistance in tobacco budworm(Lepidoptera: Noctuidae) in Texas, Mississippi, Louisiana,Arkansas, and Oklahoma. J. Econ. Entomol. 83:335-341.Roush, R. T. and R. G. Luttrell. 1987. The phenotypic expression ofpyrethroid resistance in Heliothis and implications for resistancemanagement, pp. 220-224. In Proceedings 1987 Beltwide CottonConf., National Cotton Council, Memphis, TN.Sparks, T. C. 1981. Development of resistance in Heliothis (Helicoverpa)zea and Heliothis virescens in North America. Bull. Entomol. Soc.Am. 27: 186-192.Walker, J. T., M. J. Sullivan, S. Turnipseed, M. E. Roof, and T. M.Brown. 1998. Prospects for field management of pyrethroidresistantcorn earworm (cotton bollworm) populations in SouthCarolina, pp. 1145-1147. In Proceedings 1998 Beltwide CottonConf., National Cotton Council, Memphis, TN.D. R. Cook (Corresponding Author)LSU AgCenter, Dept. of Entomology402 Life Sciences Bldg.Baton Rouge, LA 70803USAPhone (225) 578-1839Fax (225) 578-1643Email dcook@agctr.lsu.eduB. R. LeonardLSU AgCenter, Dept. of EntomologyBaton Rouge, LA 70803R. D. BagwellLSU AgCenter, Scott Research and Extension CenterWinnsboro, LA 71295S. MicinskiLSU AgCenter, Red River Research StationBossier City, LA 71113J. B. Graves (Retired)LSU AgCenter, Dept. of EntomologyBaton Rouge, LA 70803Monitoring of Insecticide Resistance in Helicoverpa armigera (Hübner) from 1998 to 2002 in Côte d'Ivoire, WestAfricaHelicoverpa armigera (Hübner) is the major insectpest of the cotton crop in West Africa. Populationsrecently developed resistance to pyrethroids via theoverproduction of oxidases. To control this pest, aresistance management strategy was applied in themajor West African cotton growing countries from1999 onwards. In Côte d'Ivoire insecticide resistance ofH. armigera was monitored in field strains from 1998to 2002 using vial tests and topical applications inthird-instar larvae. Vial tests with discriminating dosesof cypermethrin were used directly on field-collectedlarvae at the end of the cotton season. The percentageof resistant larvae varied around 67% with 6 µg/vialand around 13% with 30 µg/vial according to year andplace.Topical applications were used in the laboratoryon the first generation of populations collected fromcotton (Gossypium hirsutum), tomato (Lycopersicumesculentum), or a strongly infested ornamental flower(Antirrhinum majus) with various insecticides. Theresistance factors calculated from dose-mortalityregressions varied from 5 to 38 with deltamethrin.They were always higher for strains collected fromcotton in the Bouaké area at the end of the season.Concerning the pyrethroid alternatives currently usedin Côte d'Ivoire, no lack of susceptibility was detectedwith endosulfan and profenofos in the cotton fieldstrains showing their interest in the resistancemanagement strategy. All these results suggest arelative stability of the pyrethroid resistance in H.armigera for 1998 to 2002 and confirm the success ofthe resistance management strategy.KEY WORDS Helicoverpa armigera, insecticideresistance, cotton.INTRODUCTION More than two million small-scalefarmers are cultivating cotton in West Africa on anaverage of 1 ha plots. Cotton is one of the mostimportant cash crops in the region and provides morethan 50% of the cash to the agricultural populations. Itcontributes largely to the struggle against poverty inthe countries of the African Cotton Belt. Cotton cropsare damaged by a large number of insect species, themost harmful being the cotton bollworm Helicoverpaarmigera (Hübner). To control the whole cotton pestcomplex, available and profitable approaches includechemicals associated with the use of hairy cultivar andappropriate cultural practices. As a result, this cropreceives the largest amount of insecticide among thecrops cultivated in the area. Since the early eighties,pyrethroids have been extensively used, because theyare very efficient against bollworms at low doses andbecause their toxicity to mammals is low. However,since 1996 high infestations of H. armigera wereobserved in some areas suggesting control failure dueto the development of insecticide resistance (Vassal etal., 1997; Vaissayre et al., 1998; Martin et al., 2000). In1998, pest infestations extended to several countries inWest Africa despite an increase in spaying intensity.This event became highly threatening since similarresistance observed in India and Pakistan resulted indramatic losses of cotton production, pushing somefarmers to suicide (McCaffery et al., 1988 and 1989).Facing this problem, West African countries put51