Phytoseiulus persimilis is an active predatory mite which has specialised in feeding on mites in the family Tetranychidae. This includes the common Two-Spotted Spider Mite Tetranychus urticae, and the Carmine Mite Tetranychus cinnabarinus. It will not feed on other arthropod prey or pollen, so in the absence of spider mites it cannot become established.
Best results are obtained by releasing Phytoseiulus persimilis soon after spider mites first appear on the crop. This may occur during the spring in field crops, when conditions are suitable for diapause break. In protected crops, spider mites may enter diapause in September, but can become active again at any time from early January.
Release rates in this case tend to be in the order of 4 predators/m², with releases concentrated around recognised colonies of spider mites.
Make sure that you distribute some Phytoseiulus into the areas around the outbreaks. If this is not done, the predators may remain in areas of plentiful food, and not migrate to the edge of an infestation. Surviving spider mites at the periphery then continue to breed unchecked, and the colony may expand in a ring away from the areas with predators.