Host plant-induced susceptibility of Tetranychus urticae (Acari: Tetranychidae) to three acaricides with different mode of action

Abstract

The relationship between host plant adaptation and acaricide resistance of Tetranychus urticae Koch (Acari: Tetranychidae) were studied  through three laboratory experiments, a non-choice test to evaluate the performance, a choice test to measure the preference of T. urticae females to different host plants (Squash, cucumber and kidney bean ); and a bioassay of three reduced risk acaricides with  different mode of action (Abamectin, fenpyroximate and clofentezine) against T. urticae females. Mean fecundity in the non-choice test  was higher on kidney bean than on the other host plants. Survival of 5-day-old females was independent of the host plant. The  percentage of females that laid at least one egg did not depend on the host plant. In the choice test, hostplant preference was  independent of the host plant. The oviposition was dependent on the host plant, and a significant difference was found. Abamectin  showed the highest toxicity against T. urticae, LC₅₀ values were 0.02, 0.031 and 0.06 mg /l on squash, cucumber, and kidney bean after 72  h. respectively, which was followed by fenpyroximate, LC₅₀ values recorded 1.69, 1.75 and 3.35 mg /l on cucumber and kidney bean and squash, respectively. While clofentezine the lowest toxicity, LC₅₀ values were 6.19, 8.34 and 14.26 mg /l on kidney bean, cucumber,  and squash, respectively. Results proved the necessity of considering the host plant when studying the efficiency of the pesticides.