Abstract
Abstract The resistance to insecticides of six Sudanese strains of Aphis gossypii (Glov.) collected from cotton fields in Sudan Gezira over four consecutive crop seasons (1988, 1989, 1990, 1991) and that of two French strains, was studied in the laboratory. When compared with a known English susceptible strain, Sudanese aphids were found to be resistant to the four insecticides tested (fenvalerate, deltamethrin, endosulfan and γ‐HCH) while the French strains were relatively susceptible. Evolution of insecticide resistance in Sudanese strains over the four crop seasons was observed. The high synergist ratios and the decrease in resistance factor for the resistant strain, Sudan V, in experiments with piperonyl‐butoxide (PB), an inhibitor of mixed function oxidase, and pyrethroids (deltamethrin and fenvalerate) and also PB with organochlorines (endosulfan and γ‐HCH), suggested that enhancement of the activity of this class of enzyme was a cause of resistance in the Sudanese strain of A. gossypii.
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