Abstract
tetranychus urticae caused many problems in field crops in Egypt, despite the use of acaricides that showed loss efficiency against T. urticae so we have studied bioassays tests for certain acaricides on some Egyptian strains of T. urticae. We investigated resistance levels of different acaricides from differ groups against T. urticae. Resistant Ratio (RR), RR50 = 119.62, 19.53, 17.93 and 26.38 fold for fenpyroximate, chlorfenapyr, abamectin and bifenazate, respectively. The strain showed high levels of cross-resistance to abamectin (RR 152), moderate levels of cross-resistance to chlorfenapyr (RR 38.08) and low levels of crossresistance (RR < 10) to bifenzate. Resistance coefficient (RC) values calculated for this active ingredient 2.20 (medium resistance). Sensitivity of the mite to pyrrole and avermectin active ingredient 0.152 and 0.075 (lack of resistance). Carbazate was classified as 1.14 (low resistance). All acaricides shortened the longevity and decreased the fecundity of T. urticae resistance strain compared with the control. Life cycle of the offspring that produced from treated T. urticae females was increased in all treatments compared with the control.
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