Resistance of Mythim na separata( Lepidoptera: Noctuidae )to five different types of insecticides in Beijing

Resistance of six field populations of Mythimna separata( Walker) collected from Beijing to five different types of insecticides w as tested by leaf dip method in laboratory. The results show ed that compared w ith the relative susceptible strain of M. separata,the six field populations exhibited different level of resistance to different types of insecticides. As to chlorantraniliprole,emamectin benzoate and chlorpyrifos,the six field populations of M. separata show ed susceptible or low level resistance,w ith resistance ratio 1. 314- 4. 213 fold,1. 000- 4. 385 fold and 1. 083- 5. 936 fold,respectively. While to chlorfenapyr and lambda-cyhalothrin the resistance ratios of the six field populations of M. separata w ere 1. 355- 20. 80 fold and 1. 748- 13. 98 fold,indicating susceptible to moderate level resistance,respectively. It w as suggested that in order to delay the generation and development of insecticide resistance in M. separata in Beijing,alternative and ratational application of insecticides betw een chlorantraniliprole, emamectin benzoate, chlorpyrifos and chlorfenapyr or lambda-cyhalothrin is necessary.