STUDIES ON SELECTION AND RESISTANCE MECHANISM BY ABAMECTIN AND ETOXAZOLE IN Tetranychus urticae (Acari.: Tetranychidae)

This investigation was conductedto study the mode of development of resistance Tetranychus urticae against acaricides. A T. urticae strain was collected from cotton plants grown in the experimental farm of Sakha. After ten generations of selection with abamectin and etoxazole under laboratory conditions, the resistance strain to abamectin and etoxazole started slowly in the first generation until the fourth generation, then began to increase gradually increase until reached the highest peak at the end of the tenth generation ( developed 140 and 37.45 fold resistance, respectively), suggesting that these glutathione-S-transferase (GST), acid phosphate, alkaline phosphate, ATPase and AChE enzymes are important in conferring abamectin and etoxazole resistance in Tetranychus urticae. The major resistance mechanism to abamectin was the increasing activities of glutathione-S-transferase (GST), acid phosphate, alkaline phosphate, ATPase and AChE. The activity in resistance strain developed 602.35, 203.52, 143.87, 8.93, and 1.31 fold comparable to that in the susceptible strain, respectively, with a percentage of increase equal to 419.38 % for alkaline phosphate. The activity of GST in the resistance strain for etoxazole developed 381.56 fold when compared with the susceptible strain. While the percentage of increase was 163.82 % for AChE.