Cross-resistance to,and synergists of,acetamiprid in Aphis gossypii

[Objectives]To provide the basis for delaying and preventing resistance to acetamiprid in the cotton aphid(Aphis gossypii Glover),cross resistance to,and synergists of,this compound were studied in acetamiprid-resistant and susceptible strains of A.gossypii in the lab.[Methods]Acetamiprid-susceptible and-resistant strains of A.gossypii were developed by individual reverse and group selection.The cross resistance of acetamiprid-resistant strains to 13 kinds of insecticides and the synergistic effects of potential synergists were determined with the leaf membrane assay.[Results]Acetamiprid-resistant strains of cotton aphids exhibited about 82.33-fold resistance to acetamiprid compared with the susceptible strain.Resistant strains displayed less than 5 fold resistance to pymetrozine and methyl-abamectin,5-10 fold resistance to thiamethoxam,bifenthrin,chlorpyrifos,malathion,profenofos and Phoxim,10-15 fold resistance to endosulfan,abamectin,beta-cypermethrin,triazophos,Omethoate,and 15 fold resistance to imidacloprid.Synergism tests showed that TPP and PBO had little synergistic effect on acetamiprid in susceptible strains.However TPP and PBO had an obviously greater synergistic effect in resistant strains(SR1.77 and 1.61,respectively) than in susceptible strains(SR1.02 and 1.03,respectively).DEM had little synergistic effect on acetamiprid in both resistant and susceptible strains(synergism ratio;1.04 and 1.02 respectively) but TPP and PBO were strong synergists.The LC_(50) of susceptible strains was 0.180 mg/L.These results show that resistance to acetamiprid in cotton aphid populations in Xinjiang could potentially reach 6.1-22.0 times that of acetamiprid-susceptible strains(LC_(50)0.180mg/L).[Conclusion]There is a risk of resistance to acetamiprid in cotton aphids in Xinjiang which may be able to be managed by using pymetrozine and methyl abamectin.