Species

Predatory mites are not insects. They belong to the phylum Arthropoda. There are several different species of mites that feed on different types of pests. This fact sheet will focus on Phytoseiulus persimilis.

Identification

Life Cycle

Female mites lay approximately 60 eggs during their short life. Eggs hatch within 2-3 days and go through a larval and nymph stage before becoming adults. The length of development into adult mites varies and is directly influenced by temperature. In cooler temperatures around 60 degrees F, development can last up to 25 days, half of the mite's entire life. In warmer temperatures around 85 degrees F, development can take as little as 5 days. The average lifespan of Phytoseiulus persimilis is 50 days.

Prey

Spider mites (egg, larvae, pupae, and adult)
Thrips

Function

Phytoseiulus persimilis have extensions of their mouth that they use to attack and kill their prey. They are constantly on the move, seeking out prey, and will only stop in order to feed. This particular type of mite functions best with dense foliage that allows them to easily move from one plant to another. These mites are capable of eating up to 20 mites or eggs in one day. They are considered the most voracious and best biological control for spider mites.

Commercial Availability

Phytoseiulus persimilis are widely available for purchase through a number of online distributors.

Handling and Use

It is important to release the mites as soon as possible after you receive them. They can be stored in a cool place or in the refrigerator for up to but not exceeding 24 hours. Before release, lightly wet the foliage of the plants you are releasing them on to make it easier for them to attach. Release during the evening and refrain from watering for 24 hours to give the mites ample time to set up.

Cultivation Techniques

Phytoseiulus persimilis are voracious predators and will attack spider mite populations until they are completely wiped out. This can lead to their own starvation since spider mites are their main food source. They will move on to another area, become cannibalistic and begin preying on each other, or die of starvation. Keeping a balance on the situation is difficult due to the fact that predatory mites reproduce twice as fast as spider mites. Releasing Phytoseiulus persimilis in small amounts will help to prevent a population explosion and total destruction of their prey. If the spider mite problem is not overwhelming, releasing the predator mites at times with lower temperatures and relative humidity will help to slow the reproduction process. With predator mite population control so difficult, it comes down to having to release and rerelease the predator mites every time an outbreak occurs.

References

Flint, Mary Louise, and Steve H. Dreistadt. Natural Enemies Handbook: The Illustrated Guide to
Biological Pest Control. Berkeley: UC Division of Agriculture and Natural Resources and the University of California Press, 1998.

Lindquist, Richard K. "Predatory Mites" The Ohio State University Extension. 6 Oct 2008.
< http://floriculture.osu.edu/archive/apr99/premite1.html>.

"Predatory Mite Release Instructions." 2006. Planet Natural. 6 Oct 2008.
<http://www.planetnatural.com/site/xdpy/kb/predatory-mite-instructions.html>.

Weeden, C.R., A. M. Shelton, and M. P. Hoffman. "Phytoseiulus persimilis."
Biological Control: A Guide to Natural Enemies in North America. Cornell University.
6 Oct. 2008. <http://www.nysaes.cornell.edu/ent/biocontrol/predators/orius.html>.