BIOLOGICAL CONTROL OF THE TWOSPOTTED SPIDER MITE ON LANDSCAPE PLANT BEDS USING PHYTOSEIULUS PERSIMILIS (ACARI: PHYTOSEIIDAE) PREDATORY MITE

The twospotted spider mite, Tetranychus urticae (Acari: Tetranychidae), is a pest of landscape beds and often requires control to conserve bed quality and extend bed life. Miticides are available but often are impractical. Two experiments were conducted to evaluate a single release of Phytoseiulus persimilis (Acari: Phytoseiidae) predatory mites for spider mite control in marigold (Tagetes patula) beds in comparison to miticides and an untreated check. Programs of abamectin, bifenazate, and hexythiazox controlled the spider mites well. P. persimilis applied at 3-5 predators per plant controlled the spider mites within 4-6 weeks. Modest, but acceptable spider mite aesthetic damage occurred to plants before predators gained control. Spider mites in untreated checks exceeded 146 (experiment 1) and 211 (experiment 2) mites per leaf and resulted in unacceptable damage. P. persimilis predators can be used to control spider mites in landscape beds, extend life of beds, and eliminate objections to miticides.