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Six field-collected populations of third-instar African bollworm, Helicoverpa armigera (Hubner), (Lepidoptera: Noctuidae) were tested for their susceptibility to endosulfan, profenofos, lambdacyhalothrin and methomyl applied as topical spray. Populations were established by collecting eggs and larvae from four major cotton and two chickpea growing areas of the country to generate baseline data on the level of resistance or susceptibility to commonly used insecticides. LD50s were determined using probit analysis. High LD50 (73.47 pg/g) was recorded for samples collected from Arbaminch and the lowest for those from Dukem (21.28). The calculated resistance ratio (RR) of samples from Arbaminch for endosulfan was 3.45. The Dubti population recorded the highest LD5o and RR for profenofos. The Arbaminch population was found highly susceptible to lambdacyhalothrin with LD50 of 0.05 pg/g larval weight. High LD50 (0.52 pg/g) was recorded for Dubti population with RR of 10.40. LD50 of methomyl were very low in all populations indicating susceptibility of populations to this insecticide.
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