Effects Of Sublethal Doses Of Acetamiprid And Afidopyropen On Harmonia Axyridis(Pallas) And Lysiphlebia Japonica(Ashmead)

The cotton aphid,Aphis gossypii Glover,is an important global agricultural pest,which causes significant damage to crop plants through direct feeding and indirect virus transmission.At the present,the command of A.gossypii has been mainly dependent on the application of chemical insecticides.However,the long-term and extensive use of chemical insecticides can cause some negative effects on natural enemies of insects in the field.Harmonia axyridis（Pallas）and Lysiphlebia japonica（Ashmead）are important components of integrated pest management（IPM）,which are widely used for controlling of cotton aphids in the field.Acetamiprid and afidopyropen are two widely used insecticides in the cotton field to control A.gossypii in China.However,the effects of sublethal doses of acetamiprid and afidopyropen on H.axyridis and L.japonica,two major natural enemies of A.gossypii,remain unclear.Therefore,in this study,the effects of sublethal doses of acetamiprid and afidopyropen on these two natural enemies were investigated based on the results of determining the toxicity of these two insecticides.The main results are as follows:1.Toxicity of acetamiprid and afidopyropen to A.gossypii and its natural enemiesThe results showed that afidopyropen was highly toxic to A.gossypii(LC₅₀=1.674 mg/L),but low toxic to two natural enemies(L.japonica:LD₅₀=20.578μg/cm²;H.axyridis:LC₅₀=1308.362 mg/L),indicating that afidopyropen is an environmentally friendly insecticide.The sensitivity of A.gossypii to acetamiprid was low(LC₅₀=442.573 mg/L),while the toxicities of acetamiprid to L.japonica and H.axyridis(L.japonica:LD₅₀:0.007μg/cm²;H.axyridis:LC₅₀=0.114 mg/L)were relative higher.Therefore,the rational use of acetamiprid should be paid more attention during the control of A.gossypii.2.Sublethal effects of acetamiprid and afidopyropen on H.axyridisThe results of age-stage,two-sex life table showed that sublethal doses of acetamiprid treatments can significantly reduce the emergence rate,hatching rate,adult longevity,and fecundity of H.axyridis both in F₀and F₁generations.Moreover,the survival rate and survival time of H.axyridis were significantly reduced in the F₁generation.Similarly,sublethal doses of afidopyropen treatments can significantly prolong the development time of the larvae of A.gossypii in F₀generation,while the development duration of pupa was significantly shortened.Although sublethal doses of afidopyropen had no significant effects on the reproductive rate of F₀generation,the net reproductive rate of F₁generation was significantly reduced.Sublethal doses of acetamiprid and afidopyropen significantly reduced the predatory capacity of H.axyridis,indicating that the predation performance of H.axyridis was inhibited.In addition,the results of transcriptome analysis showed that sublethal doses of acetamiprid and afidopyropen could induce the overexpression of cytochrome P450and UGTs genes in H.axyridis,which suggests that the differential expression of these important detoxifying related genes may be involved in the detoxification of H.axyridis to acetamiprid and afidopyropen.3.Sublethal effects of acetamiprid and afidopyropen on L.japonicaSublethal doses of acetamiprid and afidopyropen significantly inhibited the adult longevity,mean generation time,and parasitism rate of L.japonica.These results expressiond that sublethal doses of acetamiprid and afidopyropen had significant negative effects on the developmental duration and parasitic function of L.japonica.