Using Acaricides in Combination with Phytoseiulus persimilis Athias-Henroit to Suppress Tetranychus urticae Koch Populations

Acaricides are often used to suppress populations of the twospotted spider mite, Tetranychus urticae Koch. Problems associated with acaricide use have led some ornamental producers to incorporate releases of the predaceous mite Phytoseiulus persimilis Athias-Henriot into pest management programs. Our objective was to determine if acaricides could be used with P. persimilis to suppress T. urticae. Ten acaricides were tested against T. urticae on infested Buddleia × davidii ‘White Profusion’ cuttings. Abamectin, chlorfenapyr, Gowan 1725, horticultural oil and neem oil suppressed T. urticae populations 3, 7 and 14 d after application. Bifenthrin suppressed T. urticae populations 7 and 14 d after application, and hexythiazox suppressed T. urticae populations 14 d after application. Azadirachtin, pyridaben and spinosad did not suppress populations. Acaricide applications followed by release of P. persimilis reduced T. urticae populations, but suppression with acaricides followed by predatory mite release was not significantly greater at all times than with acaricide applications alone, or with predator releases without previous acaricide application. Results demonstrate that efficacy is variable among the acaricides tested and that acceptable levels of T. urticae suppression can be achieved with acaricides and P. persimilis.