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Abstract The present study is directed to evaluate toxicity of six chemicals, three acaricides (abamectin, ethion, etoxazole), one pyrethroid (cyhalothrin) one mineral oil (Diver) and one plant extract (Allium sativum) against the eggs and adult females of Tetranychus urticae and two predators Amblyseius fallacis and Stethorus gilvifrons. The effect of sub lethal doses of these chemicals on some biological and behavioral aspect of the mite and the two predators were also evaluated. Also, to evaluate the toxic effect of these compounds of T.urticae on soybean plants under field conditions and the subsequent effect on weight of pods and seeds. Also, to study development of resistance to T.urticae for eight successive generations, then study the mechanism of resistance to T.urticae by evaluate activity of AChE. The results indicated that abamectin was the high toxic compound while Allium sativum was the least toxic compound to adult females and eggs of T.urticae. Diver and Allium sativum were the most safe compounds to the adults of two predators. Cyhalothrin, abamectin and ethion were the most effective compounds tested on prey eggs consumption, predators’ egg deposition and hatchability. Cyhalothrin was the most effective compound against the motile stages of T.urticae in the field, also, the compounds treatments on soybean plants gained, a yield more pronounced than that of the untreated plants. Development of resistance in susceptible strain and the resistance level of T.urticae increased gradually to reach its peak in eight generations. All tested compounds were bioassay for their effects on the activity of the enzyme. |