Compatibility of Acaricide Residues with Phytoseiulus persimilis and Their Effects on Tetranychus urticae

Abstract

The twospotted spider mite, Tetranychus urticae Koch, is a serious pest of many nursery crops. Regular acaricide applications are required to maintain acceptable population levels of this pest. Phytoseiulus persimilis Athias-Henriot is a commercially available predator used to control T. urticae populations. The effects of acaricide residues were tested on P. persimilis and T. urticae using a leaf disk system. Both species were exposed to residues for 24 hours 1, 3, 7, and 14 days after acaricide application. Abamectin, Gowan 1725, hexythiazox, horticultural oil, neem oil, pyridaben, and spionosyn residues caused no mortality to P. persimilis 1, 3, 7, or 14 days after application. Chlorfenapyr was harmful to both species at all times after application. Bifenthrin residue was toxic to P. persimilis at all times after application, but was only harmful to T. urticae up to one week after application. Tetranychus urticae mortality from Gowan 1725, horticultural oil, and neem oil residues was significantly greater than the control 24 hours after application, but not thereafter. Tetranychus urticae mortality from hexythiazox and spinosad residues was not significantly greater than the control. Proper pesticide selection may create favorable conditions for release of P. persimilis and reduce acaricide dependency.