Two-spotted spider mite (TSSM), western flower thrips (WFT), whiteflies, and the viruses they vector damage tomato and cucurbit crops in the southeastern US. This project combined conservation biocontrol and augmentative releases of the predatory mites Phytoseiulus persimilis and Amblyseius swirskii to manage this pest-disease complex. Studies were conducted to optimize timing and method of predator releases, develop on-farm rearing methods, document indigenous predators on organic farms, and evaluate impacts of NOP-allowed pesticides.

Timely release of P. persimilis controlled TSSM in field-grown organic tomato. Mites reared on TSSM infested tomato were more effective than purchased P. persimilis (propagated on beans) and the project developed a simple method for on-farm P. persimilis propagation. A. swirskii failed to establish on tomato, did not control WFT, and proved more difficult to rear on farm.  However, A. swirskii released on summer squash within 2-4 weeks after planting controlled whiteflies and sometimes reduced cucurbit viruses. Releasing mites on foliage, at plant bases, or from sachets worked equally well. Indigenous predators like the beetle Delphatus catalinae can enhance biocontrol efficacy.

Spinosyn, pyrethrin, azadirachtin, and copper pesticides harmed predatory mites while Bt, biofungicides, and peroxides did not.  Cost-efficacy of biological controls depends on suitable adjacent environments (forest, pesticide-free fields) to sustain predator populations.