Insecticide resistance studies of Cypermenthrin 25EC and Chlorpyriphos 20EC against Spodoptera litura fabricius, 1775 (Lepidoptera: Noctuidae)

Spodoptera litura is one of the important pests and causes considerable damage to the crop. The indiscriminate use of insecticides result in development of resistance. Hence experiments were planned in laboratory conditions. The pest was reared in laboratory for many generations without exposure to any insecticides during 2018–19. After ensuring infection free culture, the insecticide resistance monitoring assays were performed to determine the development of resistance against two insecticides Cypermethrin 25EC and Chlorpyriphos 20EC by leaf-dip methodology. It was performed for five subsequent generations. The experimental results indicate greater resistance developed in Cypermehtrin 25EC @ 0.5 ppm (LC 50: 0.49, LC 90: 0.94) as compared to Chlorpyriphos 20EC @ 0.05 ppm. (LC 50: 0.05, LC 90: 0.34). This shows that there is onset of resistance in Cypermethrin 25EC, which may cause adverse effects, if not used in proper rotation with other insecticides.