Insecticide Toxicity And The Effect On Behavior Of Aphidius Gifuensis Ashmead (Hymenoptera:Braconidae)

Four insecticides, including5%abamectin,5%acetamiprid,10%cis-cypermethrin and10%imidacloprid, were used to study their toxicity, parasitism, development and behavior to Aphidius gifuensis Ashmead. The toxicities of four insecticides on adult parasitoids of A. gifuensis were evaluated under laboratory condition by the methods of residual film in glass tube and feeding. The influences of four insecticides on the emergence rates of A. gifuensis were studied at sublethal concentrations of tobacco aphids, Myzus persicae (Sulzer). The results showed that both the contact toxicity and the stomach toxicity of avermectin for adult parasitoids were the strongest in these insecticides, the mortality rates at24h were87.78%and94.44%respectively; the toxicities of imidacloprid were the weakest, the mortality rates at24h were41.11%and61.11%respectively; the toxicities of the other two insecticides, alpha-cypermethrin and acetamiprid, were medium, the mortality rates at24h were37.78%,54.44%and67.78%,86.66%respectively. The emergence rates could be significantly reduced while parasitoids were treated by avermectin and acetamiprid during egg stage and treated by all four insecticides during lavar stage. However, the emergence rates were not changed distinctly while parasitoids were treated by all four insecticides during pupal stage. The sex ratio of parasitoid was significantly affected only when abamectin was used at larval stage, it was not affected by other three insecticides. But the mortality rates of parasitoids were higher when these insecticides were used at adult stage.The research on the parasitism, longevity and growth of A. gifuensis showed that four insecticides reduced the parasitism rate of A. gifuensis at adult stage. Longevity and parasitism rate were differently inhibited by insecticides at egg, larva and pupae stage. The pupa’s weight of A. gifuensis treated by sublethal concentrations of tobacco aphid at egg and larva stage had declined in different degrees. Insecticides residues tested found the residue of abamectin was the strongest, its mortality to A. gifuensis was34.44%after10d, which was higher than other treatments. Meanwhile, insecticides residues of imidacloprid and alpha-cypermethrin were lower.The selective reactions of A. gifuensis to different odor sources were performed with Y-tube olfactometer. The selective rate of A. gifuensis to abamectin, acetamiorid, imidacloprid, and alpha-cypermethrin was55.33%,53.33%,51.33%and63.33%, respectively, when four insecticides used to the tobacco with aphid. While the selective rate without insecticides tobacco with aphids was68.00%.The EAG reaction of A. gifuensis found the relative value of different treatments of male and female to trans-2-hexena and caproaldehyde was much higher. For the reaction of methylis salicylas, the relative value of female EAG with abamectin treatment was0.725, which was much higher than other insecticides treatments. In female linalool treatment, other insecticides were lower than control except alpha-cypermethrin. No significant differences in other treatments for the male and female expect abamectin and control. The EAG relative value of male and female to P-caryophyllene and alpha-pinene with four insecticides were lower.Treated by four insecticides at sublethal concentrations of A. gifuensis, moving distance, speed and probing frequency were lower than control and the acetamiorid treatment was the lowest. This indicated that the behavior of A. gifuensis were strongest affected by acetamiorid.