Predatory Mites
Order: Acari
Family: Phytoseiidae
Description
Adult predatory mites have four pairs of legs and have pear- or teardrop-shaped bodies that lack antennae and wings. Compared to spider mites, predatory mites are more active, slightly larger, and have longer legs which allows them to move faster as they search for prey. Eggs are typically laid on the underside of leaves, and are oval, clear, and larger than the eggs of spider mites.
Quick Facts
- Beneficial arthropods can prevent or limit pest problems in the yard and garden.
- These beneficial mites can be categorized broadly as either insect predators or parasites.
- Common insect parasitoids include flies and small wasps.
- When insecticides are needed, choose ones that are selective and less likely to harm beneficial insects and mites.
Predatory mite feeding on prey. Image credit: Monica Farfan, via Wikimedia Commons
Release of predatory mites in nursery planting. Many species of predatory mite are commercially available as biocontrol agents for various arthropod pests, most notably spider mites. Image credits: Whitney Cranshaw, Colorado State University, Bugwood.org
Life history and habits
Predatory mites have five life stages: egg, larvae, protonymph, deutonymph, and adult. The entire life cycle is completed in about 6-12 days. Eggs are laid individually and hatch within two to three days. After hatching, larvae of the western predatory mite (Galendromus occidentalis) begin to feed on spider mites or eriophyid mites. This species overwinters as mated adult females in crevices on tree trunks, under scales of bark, or in detritus near the bases of trees when there are fewer than 11 hours of daylight. However, non-diapausing strains are available for greenhouse pest management during short winter days.
Phytoseiulus persimilis do not begin feeding until they reach the nymphal stage. This species feeds on spider mites and thrips and will revert to cannibalism when sufficient prey is not available. These mites are voracious predators, and one P. persimilis adult can consume 5-20 prey (eggs or mites) per day. A third species of predatory mite, Neoseiulus cucumeris, is a generalist predator of whiteflies, thrips, mites, aphids, and psyllids. Like P. persimilis, the larvae of N. cucumeris do not feed.
Collectively, these three predatory mites have differing optimal temperature and relative humidity, and this information should be taken into consideration when determining which species of predatory mite to purchase. Generally, western predatory mites are less sensitive than P. persimilis to variations in relative humidity. More information on the optimal temperature and relative humidity for western predatory mite and P. persimilis is available here.
Predatory mites as biocontrol agents
All three of the predatory mites described above are commercially available for biocontrol of different arthropod pests, including thrips, spider mites, and eriophyid mites. The western predatory mite is marketed for spider mite and eriophyid mite control in orchards and low- to medium-height crops such as strawberries and grapes. Phytoseiulus persimilis is marketed for control of two-spotted spider mites in vegetables and ornamentals in greenhouses and gardens. While western predatory mites do not knock down spider mite populations as quickly as P. persimilis, they can survive longer periods without prey.
Neoseiulus cucumeris is labeled for control of thrips, two-spotted spider mites, and rust mites. This species can survive on plant pollen in the absence of sufficient prey, making it an easily adaptable natural enemy for greenhouse and nursery production systems.
Conservation
Avoiding applications of broad-spectrum insecticides or miticides will help maintain healthy populations of predatory mites. Some pesticides such as imidacloprid, carbaryl, and malathion reduce resident predatory mite populations and can exacerbate infestations of spider mites. In addition, controlling arthropod predators such as ants will help maintain populations of predatory mites in the greenhouse. Low humidity can also restrict the activity of predatory mites.
Including perennial flowers, shrubs, and trees will help establish populations of small insects and pest mites as prey for predatory mites so they are present when pest populations begin increasing. In crops, these plantings will be most effective at the borders or as intercropped strips.
References
Cornell University. (n.d.). Phytoseiulus persimilis. Cornell University – College of Agricultural and Life Sciences. Available https://biocontrol.entomology.cornell.edu/predators/Phytoseiulus.php
Hoyt, S., and E. Beers. 1993. Western Predatory Mite. Washington State University. Available https://treefruit.wsu.edu/crop-protection/opm/western-predatory-mite/
Kakkar, G., and V. Kumar. 2016. University of Florida – Featured Creatures. Available https://entnemdept.ufl.edu/creatures/BENEFICIAL/Neoseiulus_cucumeris.htm
Patterson, R., and R. Ramirez. 2012. Beneficials: Predatory Mites. Utah State University – Extension. Available https://digitalcommons.usu.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=1857&context=extension_curall
Raupp, M., J. Traunfeld, and C. Sargent. 2023. Predatory Mites. University of Maryland – Extension. Available https://extension.umd.edu/resource/predatory-mites
UCANR. (n.d.). Phytoseiulus Predatory Mites. University of California – Agriculture and Natural Resources. Available https://ipm.ucanr.edu/natural-enemies/phytoseiulus-predatory-mites/