Residual effect of neonicotinoids on the whitefly bemisia tabaci (Gennadius) in bt cotton

The residual effect of neoniotinoids viz. imidacloprid 17.8SL @ 50, 75, 100 ml/ ha, thiamethoxam 25WG @ 50, 75, 100 g/ ha and dinotefuran 20SG @ 75, 100, 125 g/ ha on the development of whitefly Bemisia tabaci (Gennadius) was evaluated during 2015-16 and 2016-17. It was found that use of imidacloprid resulted in an increase in the fecundity and a shorter lifecycle followed by thiamethoxam. On the contrary, dinotefuran decreased the fecundity and prolonged the lifecycle. Longer lifecycle will result in lesser number of generations/ year. The study indicates that neonicotinoid insecticides that are widely used on Bt cotton in North India result in an increase in the incidence of B. tabaci. However, dinotefuran being lesser used and with slightly differing mode of action will decrease the same.