Abstract
Seven insecticides i.e., trichlorfon, malathion bifenthrin, lambda-cyhalothrin, spinosad, cypermethrin and chlorpyrifos were studied for resistance against three field strains viz., M1, M2 and SWL derived from twenty nine field populations of B. zonata. Results showed that high resistance ratios were found towards trichlorfon (80.81-, 35.91- and 69.92-fold), while moderate resistance ratios were recorded to malathion and chlorpyrifos in three selected strains (28.15-, 20.96-, 27.22 and 25.52-, 17.79-, 24.81-fold). The selected strains (M1, M2 and SWL) exhibited low to moderate resistance ratios against pyrethroids (Bifenthrin, lambda-cyhalothrin, cypermethrin) and microbial insecticide (Spinosad). It is concluded that the three field selected strains had developed more resistance against organophospahtes (Trichlorfon, malathion and chlorpyrifos) as compared to pyrethroids (Bifenthrin, lambda-cyhalothrin and cypermethrin) and microbial insecticide (Spinosad).
