Effect of Insecticides on Esterase Activity in Beet Armyworm (Spodoptera exigua

The effects of acephate, chlorpyrifos, methomyl, cypermethrin and chlorfluazuron on the carboxylesterase and acetylcholinesterase activity of beet armyworm (Spodoptera exigua) were studied, and the esterase activity in different instar larvae were compared. The results showed that the inhibition ratios of 94.69% , 93.12%, 71.90%,60.56%, 61.83% in CarE activity and 84.37%, 81.30%, 71.19%, 21.79% , 25.46% in AChE activity were obtained after the second-instar larvae were fed with leaves treated with chlorpyrifos (1 000 mg/L), acephate (3 000 mg/L), methomyl (1 200 mg/L), chlorfluazuron (50 mg/L) and cypermethrin (1 000 mg/L). The CarE activity increased with the larval development, there was no significant difference in AChE activity between second-instar larvae and fourth-instar larvae.