Sublethal effects of two common acaricides on the consumption of Tetranychus urticae (Prostigmata: Tetranychidae) by Phytoseius plumifer (Mesostigmata: Phytoseiidae)

An understanding of the sublethal effects of pesticide residues on phytoseiid mites is important to successful augmentation and conservation programs. We assessed the residual and sublethal effects of four concentrations of fenpyroximate (LC5, LC10, LC20 and LC30) and three concentrations of abamectin (LC10, LC20 and LC30) on prey consumption rates of exposed females of Phytoseius plumifer (Canestrini & Fanzago) and their offspring when fed Tetranychus urticae Koch. Prey consumption of female mites was strongly affected by treatment with all concentrations of the two acaricides. Throughout the study, females exposed to fenpyroximate showed a more extreme reduction in prey consumption than those exposed to abamectin. In contrast, abamectin affected the prey consumption of the subsequent generation of females to a greater extent than fenpyroximate. Of the subsequent generation, total protonymphal and total nymphal prey consumption were adversely affected by both acaricide treatments at the highest concentration. Deutonymph prey consumption of fenpyroximate exposed females was reduced, but not of abamectin exposed ones. Total nymphal offspring prey consumption did not significantly differ between the two acaricide treatments. In conclusion, use of either acaricide decreased the predation rate of P. plumifer, and this effect should be considered when designing integrated management programs.