Abstract: The selection for resistance by abamectin, pyridaben and fenpropathrin to Tetranychuc urticae were carried out in laboratory, as well as activity change of detoxicant enzymes. The susceptible population of T. urticae was separately treated with abamectin, pyridaben and fenpropathrin imitating field chemicals selection pressure in order to breed its resistance. The results showed that the resistance of T.urticae had reached 6.72fold to abamectin, 19.9fold to fenpropathrin and 12.1fold to pyridaben after 12 generations treatment. The resistance mechanism was evaluated by activity measurement of enzymic inhibitors and detoxicant enzymes. It was concluded that the rise of resistance to abamectin was mainly associated with increased activities of mixedfunction oxidases and glutathione S-transferase; the resistance to pyridaben was attributed to increased activIties of carboxylesterase and mixedfunction oxidases; the main cause of resistance to fenpropathrin was the increased activities of carboxylesterase and glutathione S-transferase.

Key words: Tetranychus urticae; abamectin, pyridaben, fenpropathrin, resistance selection, detoxicant enzymes