Effects of different genotypes of soybean on the susceptibility of Spodoptera litura (Fabricius)to insecticides

The results of bioassays showed that the larvae of Spodoptera litura(Fabricius)fed with different genotypes of soybean had remarkable differences in susceptibility to beta-cypermethrin. Compared with the larvae fed with highly susceptible, susceptible and mediate resistant soybean varieties, the larvae fed with resistant and highly resistant soybean varieties were more sensitive to beta-cypermethrin. The larvae fed with all different genotypes of soybean had little differences in susceptibility to phoxim, LC_(50) were 3.98-7.66 mg/L,except the highly resistant soybean variety,which was more sensitive to phoxim than that fed with other varieties,LC_(50) was 2.43 mg/L,the index of relative toxicity was 3. The larvae no matter fed with highly susceptible or highly resistant soybean varieties all had remarkable differences in susceptibility to beta-cypermethrin but little differences in susceptibility to phoxim by varying tested materials.