Selective toxicity of three acaricides to the two-spotted spider mite Tetranychus urticae and predatory mite Phytoseuilus persimilis in apple orchards

Abstract

In Egypt, phytophagous mites are serious pests on crops, vegetables and fruits and frequently cause considerable losses in plant yields. Some commercial acaricides with a degree of selective toxicity towards two-spotted spider mite are Tetranychus urticae Koch (Acari: Tetranychidae), but its selective toxicity towards Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) is under debate. In this study, the field experiments were conducted to evaluate the selectivity of three acaricides on motiles of both two-spotted spider mite and its predator P. persimilis after 3, 7, 14, 21 and 30 days of treatment. Acaricides were sprayed at 1 and 1/2 field recommended rate on apple orchards; flufenoxuron (60.00 and 30.00 mg a.i., L -1), fenpyroximate (25.00 and 12.50 mg a.i. L -1) and abamectin (7.50 and 3.75 mg a.i., L -1). All tested acaricides affected the two mite's survival; the T. urticae was more susceptible to flufenoxuron application than the P. persimilis. Results showed that half of the recommended rate of flufenoxuron showed slightly toxic effect on P. persimilis after 30 d. Flufenoxuron exhibited moderate toxic to the predatory mite at the two field rates after 14 days and was favorably selective (more toxic to T. urticae than to P. persimilis) at all tested periods. In contrast, fenpyroximate and abamectin were found to be very toxic to the predatory mite at recommended field rate after 30 days and unfavorably selective (more toxic to P. persimilis). In conclusion, fenpyroximate and abamectin should be used carefully in Integrated Pest Management programs. © 2011 Academic Journals Inc.