Hosts or Prey
Plant-feeding spider mites (family Tetranychidae)
Identification
Adults are pear shaped, bright reddish to orange, and about 1/50 inch (0.5 mm) long. Nymphs (immatures) resemble small adults and are pale salmon-colored. Although very small, P. persimilis can be distinguished with a hand lens. In comparison with its prey, P. persimilis is faster moving, slightly larger, and commonly colored differently.
Eggs are oval, approximately twice as large as spider mite eggs. Eggs are pale orange when laid, but darken as they age and approach hatching.
Lookalikes
The twospotted spider mite, Tetranychus urticae, develops a reddish color overwinter, and P. persimilis commonly occurs where twospotted mite is found. Two dark blotches on the abdomen of T. urticae generally distinguish it from P. persimilis.
Euseius species predatory mites become reddish when they feed on citrus red mites, and Euseius and Phytoseiulus species can occur together. Euseius species prefer to feed on plant-feeding spider mites that do not produce abundant silk. Phytoseiulus species prefer spider mites that produce abundant silk, such as twospotted mite. Expert examination of microscopic characters is required to reliably distinguish the species.
Life Cycle
Phytoseiulus species hatch from an egg and develop through a six-legged larval stage and two eight-legged nymphal stages before maturing into adults. Phytoseiulus persimilis feeds, reproduces, and completes development only on plant-feeding mites that produce abundant silk.
The adult female can lay up to 60 eggs during her approximately 50-day lifespan when temperatures average 74°F. Eggs hatch 2 to 3 days after being laid. Total time from egg to adult ranges from about 25 days at 59°F to 5 days at 86°F. Generation times are 7 to 17 days at common field and greenhouse temperatures, twice as fast as that of its prey.
Phytoseiulus persimilis does not have a diapause (resting) stage and is active year-round in greenhouses, interior plantscapes, and where winter temperatures are mild. There are multiple generations per year.
Habitat
Phytoseiulus persimilis can be common in greenhouses, interior plantscapes, and most any crop infested with twospotted spider mites or other Tetranychinae. Larvae of P. persimilis do not feed, but adults and nymphs prey on all stages of spider mites.
Phytoseiulus persimilis is a voracious feeder, having the highest known consumption rate of all Phytoseiidae. Adults consume 5 to 20 prey (eggs or mites) per day. If spider mite prey are not present, these predators will disperse or starve and so may need periodic reintroduction when spider mites recolonize plants. Phytoseiulus persimilis is a more effective predator where adjacent plants touch because touching plants facilitate the predator's dispersal and prey finding (locating).
Phytoseiulus persimilis requires high relative humidity to thrive. Development almost stops at 25 to 30% relative humidity. Humidity levels below 70% reduce the ability of immatures to molt to the next life stage.
Commercial Availability
Phytoseiulus persimilis can be purchased for release in crops such as caneberries, floriculture and ornamental nurseries and strawberry. If purchase and release of P. persimilis is being considered, to make this more effective control ants, reduce dustiness (e.g., periodically hose off shrubs), and avoid the application of broad-spectrum, persistent insecticides and miticides for all pests. See Natural Enemy Releases for Biological Control of Crop Pests, Protecting Natural Enemies and Pollinators, and Vendors of Beneficial Organisms in North America for more information.
Species
Over 100 species of Phytoseiidae predatory mites occur in California. These include at least 7 Phytoseiulus species.
More Information
- Phytoseiidae Database: A Website for Taxonomic and Distributional Information on Phytoseiid Mites (Acari) (PDF), Fundaçao de Amparo a Pesquisa do Estado de Sao Paulo
- Phytoseiulus persimilis, University of Florida
- Phytoseiulus persimilis (Acarina: Phytoseiidae), Cornell University
- Protecting Natural Enemies and Pollinators, UC Integrated Pest Management Program
Scientific classification:
- Phylum: Arthropoda
- Class: Arachnida
- Order: Acari
- Family: Phytoseiidae
