Lethal and sublethal effects of imidacloprid on Anagrus nilaparvatae (Hymenoptera: Mymanidae), an egg parasitoid of the rice planthopper, Nilaparvata lugens (Homoptera: Delphacidae).

Lethal toxicity of two concentrations of imidacloprid(37.5,15.0 g·hm-2) against Anagrus nilaparvatae,an egg parasitoid of the rice planthopper,Nilaparvata lugens were assessed in this study.Mortalities of adult wasp exposure to high concentration of imidacloprid reached 100% at 1.5 h exposure-period,and mortalities of adult wasp exposure to low concentration of imidacloprid reached 100% at 2.0 h exposure-period.They were both significantly higher than that of the control [(1.67±1.67)% mortality].The emergence rate of A.nilaparvatae in rice plants treated with high concentration of imidacloprid was(83.53±1.81)%,which was significantly lower than that of the control [(92.09±0.75)%].Imidacloprid was toxic to adult parasitoid with a LC50 value of 790.89 μg·kg-1.Then,two sublethal concentrations(250,500 μg·kg-1) were selected to evaluate the sublethal effect of imidacloprid on A.nilaparvatae.After exposure to two sublethal concentrations of imidacloprid,40% or 65% survived individuals had no response to volatiles from rice plants infested by N.lugens.The survived individuals who had response can not distinguish volatiles from N.lugens damaged plants or healthy plants.However,compared to the untreated control,the surviving A.nilaparvatae treated with imidacloprid had same response to kairomone of N.lugens and exhibited same parasitizing capacity.