Abstract: Distribution of carboxylesterase (CarE) and glutathione-S transferase (GST) in the midgut, fat body, head and epidemis tissues of Dendrolimus superans 6^th instar was determined. The results showed that both CarE and GST distributed in all the four tested tissues, however, CarE predominated in midgut (61.36%) while GST in fat body (36.15%). The susceptibility of CarE and GST to DDVP, avermectins and lambda-cyhalothrin was also measured in vitro. The three pesticides had different degree inhibition to either CarE or GST. There were distinct dose-effect relationships between each pesticide and each enzyme. DDVP showed the highest inhibitive effect to CarE(IC₅₀<1.000×10^-4 mg ·mL^-1), followed by avermectins (IC₅₀=1.259×10^-2 mg ·mL^-1) and then lambda-cyhalothrin (IC₅₀=4.529×10^-1 mg ·mL^-1). However, avermectins showed the highest inhibitive effect to GST, followed by lambda-cyhalothrin, DDVP showed the weakest inhibition to GST. The IC₅₀ values were 8.044×10^-3, 9.224×10^-3 and 1.755×10^-2 mg ·mL^-1 respectively. These results provide important information for reasonable insecticide application to control D. superans.

Key words: Dendrolimus superans, carboxylesterase, glutathione-S transferase, pesticide, sensitivity