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Abstract
The resistance to certain chemical insecticides belonging to different groups was investigated in 4 field strains of the cotton aphid, aphis gossypii (glover) (homopetra : aphididae) collected from Behiera, Dakahlia, Menoufia and Beni Suef governorates of Egypt during 2008 - 2010 cotton growing seasons. Slide - dipping method was followed. Results indicated that the organophosphates profenofos and chlorpyrifos were the most effective insecticides and recorded the least resistance levels and the highest toxic action when compared with the other tested organophosphorus compounds. A similar result was obtained in the case of the carbamate carbosulfan, the pyrethroid deltamethrin and the neonicotinoids imidacloprid and acetamiprid. The rest of tested insecticides showed moderate to high levels of resistance combined with low toxicities. chlorpyrifos methyl, chlorpyrifos ethyl, carbosulfan, deltamethrin, imidacloprid and acetamiprid may be recommended for the integrated management of cotton aphid. Enzyme activities of esterases and acetylcholinesterase (AChE) were also investigated in 6 field strains of cotton aphid. Field strains exhibited higher levels of Ü - and Ý - esterase activities and lower AChE activity than those achieved for the susceptible strain. Esterases seem to play an important role in insecticide resistance to the different groups. AChE may also play a role in the resistance to organophosphates and carbamates resistance was recognized but all correlations were statistically insignificant. In conclusion, esterase and AChE activities seem to be unrelated to insecticide resistance