Asian Journal of Research in Biosciences

The peach-potato aphid Myzus persicae (Sulzer) is a series pest in Egypt plantations and control require some information to be effective. Toxicity and biochemical tests were completed on greenhouse, susceptible and resistant strains reared in laboratory. Results confirmed that the toxicity arrangement of insecticide was carbosulfan was the most effective, then imidacloprid, α-cypermethrin and profenophos was the least effective on the susceptible, greenhouse and in resistant strains. Resistance ratio values refer to slight resistance developed through short time of selection, RR for resistant strains ranged between 1.3 to 2.4 times for carbosulfan and α-cypermethrin respectively and does not exceed. The biochemical measurements of enzyme activities exhibited small decreases or increases in treated aphid body homogenate than untreated. Non-Linear regression analyses revealed strong relationship between enzyme activities and pesticide LC₅₀s. There were negative correlations between most of enzyme activities and insecticide resistance. Determination of resistance mechanisms in M. persicae resistance according to the biochemical evaluation revealed higher acetylcholinesterase metabolism or esterase elevations found in the resistant strains. The LC₅₀ values exceeding the registered field dose. Synergism experiments suggested that P₄₅₀ monooxygenases and detoxification enzymes were involved in resistance to these insecticides. Therefore, the strong resistance phenotypes, with accumulation of multiple resistance mutations, over expression of P450s and other detoxification genes in the same field population presumably exist.