Studies On Resistance Of Grain Aphid (Sitobion Avenae) To Neonicotinoid Insecticides

In this study, sensitivity to 5 neonicotinoid insecticides imidacloprid, acetamiprid,imidclothiz, thiamethoxam and nicotine was detected in grain aphid (Sitobion avenae) collected from five sites Yuxian(Hebei), Yangling(Shaanxi), Yan'an(Shaanxi), Chengdu(Sichuan) and Bengbu(Anhui) in China; the relative fitness in imidacloprid-resistant strain was studied by comparing the life table of imidacloprid-resistant strain of the Sitobion avenae with that of imidacloprid-sensitive strain of the Sitobion avenae; morever, the synergistic action of enzyme-irthibitors and activity of metablic enzymes were tested;biochemical mechanisms of resistance to imidacloprid in Sitobion avenae was studied. The results were summaried as follows:1. Significant difference exsits in susceptibilities of populations of Sitobion avenae in different areas to the five neonicotinoid insecticides, the population from Bengbu(Anhui) was 119.6, 95.7 and 16.5 times less sensitive to imidacloprid, acetamiprid and imidaclothiz than the population from Yuxian (Hebei). The sensitivity to imidacloprid of the population from Sichuan and the population from Yangling is 5.7 and 5.0 times lower than the population from Yuxian. While the sensitivity to thiamethoxam of Yangling(Shaanxi) population is 5.3 times lower than the population from Yan'an (Shanxi). The populations from the five areas mentioned above had not developed obvious resistance to nicotine.2. The difference in reproductive ability of the imidacloprid-resistant strain and the susceptible strain of Sitobion avenae was found by comparision of life tables of the imidacloprid-resistant strain and the susceptible strain, and the imidacloprid-resistant strain exhibited obvious reproductive disadvantages, compared with susceptible strain. The fitness of the imidacloprid-resistant strain was evaluated by the net reproductive rate (R₀) and intrinsic rate of increase (r_m), with susceptible strain as standard. The relative fitness value for the imidacloprid-resistant strain was calculated to be 0.5200 and 0.7481.3. By comparision of activities of resistance-related enzymes in the imidacloprid -resistant strain and the susceptible strain, and of studies on the synergistic effect of the synergists on the usual insecticides in the imidacloprid -resistant strain, it was confirmed that resistance to imidacloprid of Sitobion avenae was related with significant increasing of activities of glutathione S-transferase, carboxylesterase and mixed functionoxidase in resistant strains. The result of studies on the kinetic parameters (Vmax and Km) of some resistance-related enzymes showed that there were no changes in the quality of carboxylesterase in resistance strains.