The effects of avermectin on carboxylesterase and acetylcholinesterase of Ceratovacuna lanigera

The toxicity of avermectin and its effects on carboxylesterase (CarE) and acetylcholinesterase (AChE) in Ceratovacuna lanigera Zehntner were studied by leaf immersion method and ultraviolet spectrophotometry. The bioassay results showed that the LC50 of avermectin on C.lanigera was 2.400×10 -2 mg·mL -1. The esterase activity assay indicated that activity of β-NA CarE was higher than that of α-NA CarE in C.lanigera. The activity of α-NA CarE increased with the increase of avermectin concentrations, but it began to decrease gradually when the concentration of avermectin got to 4.500×10 -2 mg·mL -1. The activity of β-NA CarE increased with increasing of avermectin concentrations. So, it suggested that a positive correlation might exist between the dose of avermectin and the activity of β-NA CarE in C.lanigera, and that the activity increase of β-NA CarE might induce resistance of C.lanigera to avermectin. With the increase of avermectin concentration, no linear correlation between AChE activity and concentration of the pesticide was observed, for that the activity was the highest when the concentration of avermectin got to 2.250×10 -2 mg·mL -1, but it decreased to the lowest when the concentration was 4.500×10 -2 mg·mL -1, then it increased slowly with the increase of avermectin concentration.