Acaricides sublethal effects are more harmful to predatory mite Phytoseiulus macropilis Banks (Acari: Phytoseiidae) than to the pest Tetranychus urticae Koch (Acari: Tetranychidae)

Abstract

Objectives: To evaluate the lethal and sublethal effect of the abamectin and dimethoate acaricides on the predator P. macropilis and its prey T. urticae. Scope: Lethal and sublethal effect of acaricides on P. macropilis and T. urticae. Methodology: The lethal and sublethal effect of the abamectin and dimethoate acaricides on the predator P. macropilis and its prey T. urticae was determined in laboratory experiments. Main results: T. urticae was 2.6-fold and 4.2-fold more tolerant than P. macropilis to abamectin and dimethoate, respectively. The instantaneous rate of increase of prey and predator decreased linearly with increasing concentrations of both acaricides. However, the instantaneous rate of increase of the predator population decreased more rapidly than that of the pest, resulting in extinction of predator populations, whereas the pest population persisted. Conclusions: Farmers may achieve better control by not spraying acaricides, but managing the populations of this predator in the field using natural enemy conservation techniques.