The roles of carboxylesterase and AChE insensitivity in malathion resistance development in brown planthopper

Malathion resistance of brown planthopper (Nilaparvata lugens Stl) wa s selected in laboratory and the successive changes in carboxylesterase (CarE) a nd AChE were also analyzed. The results showed that the speed of r esistance selection varied with generations. The biggest change of LD 50 oc curred between the 3rd－5th generations. The rise of carboxylesterase activity was cor related with the change in malathion resistance for the first 5 generations, whi le change in AChE sensitivity between 6th－8th generations had a higher correlat ion with the resistance development. Therefore, it was concluded that carboxyles terase activity increase play important role in the early stage of the resistanc e development and the AChE insensitivity at the late stage.