Clover mites are swarming in and on homes

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.  

Several folks sent in to Diagnostic Services, clover mites, Bryobia praetiosa (Acarina: Tetranychidae) that they found by the hundreds or thousands on the outside of their homes. (view photos) Many had found their way inside, as well. Clover mites are among the smallest home invaders we have in Michigan. They belong to the spider mite family, Tetranychidae, and as the name implies, they feed on clovers and grasses.  People often mistake clover mites for minute six legged insects because their front legs are considerably longer than the others, and they are projected forward giving them the appearance of antennae (as we all know, mites do not have antennae). Lush growing, well-fertilized lawns tend to produce the largest number of clover mites. For whatever reason, newly established lawns also seem to harbor large numbers of clover mites.  When conditions are right, clover mites can invade homes by the thousands. This normally happens in the spring, but fall invasions also occur. They are small enough to crawl right through window screens and through cracks around windows, doors and other external openings. If they are crushed during attempts to wipe them up, they can leave tiny red stains.

Clover mites are usually a temporary nuisance.  They appear suddenly and are generally gone a few days later. Household aerosol insecticides can be used to kill the mites indoors, if deemed necessary, but a soapy rag or wet sponge work just as well on indoor surfaces.  A vacuum cleaner equipped with a hose and a soft brush attachment will also work. Wipe or brush carefully to avoid crushing the mites and causing stains.  Mites can be removed from the outside of buildings with a garden hose.  An insecticidal soap can be concocted by using regular liquid dish-washing soap mixed at the rate of 2 tablespoons per gallon of water. These water-based treatments will not provide any residual control. A more aggressive approach, would be a perimeter treatment of a persistent insecticide along the outside walls and extending about 10 feet out from the foundation.
The best long-term method for reducing persistent clover mite invasions, is by providing a grass-free band, 18-24 inches wide, around the house. This can easily be accomplished by open areas of course sand or pea stone, or by installing a plant bed. Removing clovers and other groundcovers from the lawn, may also help prevent mite numbers from building up in lawns.

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