Selective toxicity of insecticides on Cornegenapsylla sinica Yang et Li and its predatory ladybirds

The toxicity and selectivity of various insecticides on Cornegenapsylla sinica Yang et Li and two predatory ladybirds were studied.The results showed that the selective toxicity of imidacloprid and thiamethoxam were highest among 10 tested insecticides.The selective toxicity ratio(STR on ladybird,LC50/pest LC50)of imidacloprid and thiamethoxam on Propylaea japonica were 11.10 and 10.36,respectively,and on Chilomenes quadriplagiata,10.05 and 7.06,respectively.The insecticides,fipronil and avermectin,displayed greater STRs than other insecticides,except imidacloprid and thiamethoxam,on predatory ladybirds.Among 5 pyrethroid insecticides,alphacypermethrin exhibited the highest selectivity on P.japonica and C.quadriplagiata with STRs of 1.83 and 1.43,respectively.Cyhalothrin and deltamethrin exerted the highest toxicity on C.sinica Yang et Li,but rendered lowest STRs on the predatory ladybirds.Chlorpyrifos showed the lowest selectivity on the predatory ladybirds,P.japonica and C.quadriplagiata,with STRs of 0.42 and 0.34,respectively.