Abstract: 【Aim】 The objective of this research was to establish susceptible toxicity baselines of two wheat aphids Rhopalosiphum padi and Sitobion avenae to 22 insecticides. 【Methods】 The method of the residual film in glass tube with 3 h exposure to insecticides was employed for determining toxicity of insecticides to both wheat aphid species, which were originally collected from different provinces of China during 2005-2007 and reared on wheat seedlings in the laboratory for more than 30 generations. 【Results】 In R. padi, the LC₅₀ values of susceptible toxicity baselines were 0.02 and 0.007 μg/cm² for neonicotinoid insecticides, imidacloprid and acetamiprid respectively; 0.124 μg/cm² for pymetrozin; 0.0026-0.70 μg/cm² for carbamate insecticides, carbosulfan, thiodicarb, methomyl, pirimicarb and carbaryl; 0.005-0.065 μg/cm² for organophosphate insecticides, triazophos, profenofos, omethoate, dimethoate, malathion, phoxim, dichlorvos and chlorpyrifos; 0.033-0.240 μg/cm² for pyrethroid insecticides, lamba-cyhalothrin, beta-cypermethrin, deltamethrin, bifenthrin, fenvalerate and cypermethrin.In S. avenae, the LC₅₀ values of susceptible toxicity baselines were 0.15 μg/cm² and 0.12 μg/cm² for neonicotinoid insecticides, imidacloprid and acetamiprid respectively; 0.41 μg/cm² for pymetrozin; 0.005-0.76 μg/cm² for carbamate insecticides carbosulfan, thiodicarb, methomyl, pirimicarb and carbaryl; 0.018-0.36 μg/cm² for organophosphate insecticides, triazophos, profenofos, omethoate, dimethoate, malathion, phoxim, dichlorvos and chlorpyrifos and 0.20-2.94 μg/cm² for pyrethroid insecticides, lambacyhalothrin, beta-cypermethrin, deltamethrin, bifenthrin, fenvalerate and cypermethrin. 【Conclusion】 Susceptible toxicity baselines of both R. padi and S. avenae to 22 insecticides established in this study could be used as a reference for resistance monitoring or other related researches. The insecticide susceptibility is higher in R. padi than in S. avenae for most of insecticides.

Key words: Wheat aphid, Rhopalosiphum padi, Sitobion avenae, residual film method, susceptible toxicity baseline, insecticide, resistance monitoring