Field resistance to insecticides in whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) population on okra and cotton

Abstract

Whitefly, Bemisia tabaci is an important sucking insect pest on many crops including vegetables. It has become a pronounced pest by vectoring plant viruses especially begomoviruses. In recent years, there is severe incidence of these viruses in vegetables viz., okra, tomato, chillies etc., This may be due to changes in the whitefly population itself particularly their response to insecticides. The current level of resistance in B. tabaci to selected insecticides, viz., thiamethoxam 25% WG, imidacloprid 17.8% SL, thiacloprid 21.7% SC, triazophos 40% EC and chlorpyrifos 20% EC were assayed in Madurai and Salem districts of Tamil Nadu where there was severe incidence of okra enation leaf curl virus (OELCV) and bhendi yellow vein mosaic virus (BYVMV) was noticed. Susceptibility of these populations had varied and however, had shown significant resistance to these insecticides. The highest level of resistance to thiamethoxam, imidacloprid, thiacloprid, triazophos and chlorpyrifos in terms of resistance ratio (fold increase in LC50 over the susceptible laboratory population) was registered in the B. tabaci population collected from Tirumangalam (34.54), Attur (69.41), Attur (25.15), Melur (30.92) and Usilampatti (38.67) locations, respectively. This level of resistance may lead to increased damage of host crops by whiteflies and associated spread of begomoviruses. Hence, insecticide resistance management strategies are needed to be adopted to smother the whitefly population besides continuously exploring the host plant resistance strategies.