Abstract: 【Aim】 To clarify the development of resistance to imidacloprid and the related enzyme mechanism of cross-resistance to other neonicotinoids, clothianidin and acetamiprid, the imidacloprid-resistant strain of the contton aphid, Aphis gossypii, was continuously selected in the laboratory after we found a mutation in nicotinic acetylcholine receptor (nAChR) β1 subunit. 【Methods】 Leaf dipping method was used to select the imidaclopridresistant strain of A. gossypii and to test the cross-resistance to acetamiprid and clothianidin. The LC₂₀ of acetamiprid and clothianidin were applied to the imidacloprid-resistant strain, and the effects on activities detoxifying enzymes and biological characteristics were determined with biochemical method and the systematic observation, respectively. 【Results】 The resistant strain of A. gossypii was continuously selected with imidacloprid for 75 generations and the resistance ratio reached to 72.6-fold as high as that of the susceptible strain. When resistance selection was suspended in the next successive 12 generations, the resistance of aphids just decreased to 72.0-fold as high as that of the susceptible strain. By generation F₇₅₊₁₂, the strain showed 11.9-fold and 20.1-fold cross-resistance to acetamiprid and clothianidin, respectively. Clothianidin could significantly inhibit the activities of CarE, GST and AChE of the imidacloprid-resistant cotton aphid, while acetamiprid showed little effect on their activities. Clothianidin had stronger inhibition on honeydew excretion and bodyweight gain of A. gossypii than other two insecticides. 【Conclusion】 The results demonstrate that the imidacloprid-resistant mutation strain not only has high-level resistance to imidacloprid, but also the resistance can be stably inherited. Therefore clothianidin has a great application value in control of the imidacloprid-resistant mutation strain of cotton aphid.

Key words: Aphis gossypii, imidacloprid, clothianidin, resistance, cross-resistance, enzyme mechanism