Effects Of Sublethal Concentration Of Avermectin On Frankliniella Occidentalis And Its Predatory Enemy Amblyseius Cucumeris

In this paper, the effects of sublethal concentration of avermectin on Frankliniella occidentalis and its predatory enemy Amblyseius cucumeris were studied. The main results were as follows:1 The toxicity of avermectins against Frankliniella occidentalis nymphaeThe toxicity of avermectin against F. occidentalis nymphae was tested in Müinger cell in laboratory. The regression equation was Y=7.15+1.29X. Three sublethal concentrations of avermectin were chosen from the equation as 0.002mg/L (LC₁₀), 0.006mg/L (LC₂₅),0.02mg/L(LC₅₀).2 Effects of sublethal concentration of avermectin on F. occidentalisThe three sublethal concentrations of avermectin had significant effects on oviposition of F. occidentalis female adults. The number of oviposition per female adult had significant difference between different treatments. The number of oviposition of F. occidentalis female adults under LC₁₀, LC₂₅ and LC₅₀ treatments dropped 37.2%, 49.4% and 66.5% respectively. Avermectin also had significant effects on the growth of F. occidentalis nymphae and the different treatments had significant difference. The observation with Ethovision behaviour observation instrument showed that the residence time of F. occidentalis 1st instar nymphae had no significant difference between Ck and LC₁₀ treatments, but had significant difference between Ck and LC₂₅ treatments after 1h and between Ck and LC₅₀ treatments.3 Effects of sublethal concentration of avermectin on predatory behaviour of A. cucumerisA.cucumeris preferred 1st instar nymphae to other instar nymphae of F. occidentalis, but the predatory capacity of A.cucumeris to F.occidentalis declined significantly under LC₅₀ concentration treatment of avermectin. The observation with Ethovision behaviour instrument showed that the residence time of A.cucumeris had no significant difference between Ck and avermectin treatments.4 Evaluation of negative effects of sublethal concentration of avermectin on A.cucumerisDifferent sublethal concentrations of avermectin had different effects on A.cucumeris. The LC₁₀ treatment had no effects on the survival rate of A.cucumeris, but had effects on its oviposition. The LC₂₅ and LC₅₀ treatments not only had effects on the survival rate of A.cucumeris, but also made 33.5% and 59.3% reduction in the number of oviposition of A.cucumeris female adults respectively.According to the determination method and standard of EPPO and IOBC about the effects of insecticides on natural enemies, the LC₁₀ of avermectin to F. occidentalis was harmless to A.cucumeris and the LC₂₅ and LC₅₀ were slightly harmful to A.cucumeris.