Higher activity of Glutathione S-transferase enzyme is associated with field evolved resistance in Empoasca flavescens Fabricius

Empoasca flavescens Fabricius is one of the most important sucking pests of tea. Earlier this pest was considered as minor pest of tea. But this has become a serious pest in Sub-Himalayan tea plantations of West Bengal, India. In spite of routine application of insecticides there were some incidences of management failure of this pest. Considering the importance of the problem to the tea industry, the present experiments were conducted with the objectives to study the insecticide susceptibility status of E. flavescens and to study the role of Glutathione S-transferase activity. Three commonly used neonicotinoids and three synthetic pyrethroids i.e., total six insecticides were tested against five populations of E. flavescens. Bioassay experiments were conducted with the field collected populations and Glutathione S-transferase activities were estimated. Resistance to the tested insecticides was very low (< 2.5-fold). It seems that resistance development against the tested insecticides was in initial stage. Thiamethoxam was found to be the least toxic insecticide and clothianidin was the most toxic insecticide. Higher activity of GST was found to be associated with the reduced susceptibility against the tested insecticides. As very low level of resistance against the tested insecticides was detected, use of these insecticides may be continued for management of tea greenfly but chemicals having similar mode of action should not be used repeatedly. Clothianidin and deltamethrin were found to be the two potent molecules against tea greenfly.