Clover mites are a common nuisance in and around Minnesota houses. Although most noticeable in the fall and again in the spring, they also may be troublesome on calm, sunny days in the winter. This pest is not an insect but a true mite, slightly smaller than the head of a pin with a reddish or reddish-brown body. When the mites are crushed, they leave rusty or blood-red spots.
Clover mites actually do not damage a house, its furnishings, or even humans or animals. They feed primarily on the lawn where they suck sap from grasses, clover, and other plants. In the fall they sometimes gather in tremendous numbers on walls, windows, tree trunks, and other outside surfaces where they seek protected hiding places. They crawl into cracks around windows or in foundation walls and under siding, shingles, or shakes. This activity often leads many of the mites into houses where they can be seen on window sills, walls, tables, etc.often in great numbers. But whether indoors or out, most of the mites will congregate on the sunny side of the house.
Cold weather tends to slow down or stop the mites' activity, which resumes again in the spring; however, on especially sunny days, they may be seen even in the winter. With the advent of warm weather, the mites become active again and ultimately return to the lawns to feed.
If only small numbers of clover mites are being found, use a vacuum or wipe up the mites with a damp cloth to remove them. Be careful not to crush the mites as they can stain surfaces.
If you having a problem with large numbers entering your home, you can treat the foundation to deter them with a residual insecticide, such as permethrin, bifenthrin, or cyfluthrin (be sure it is labeled for spraying the outside of homes). You can also consider hiring a professional pest control service to treat your home’s exterior.
If you deal with this problem most years and are looking for a more sustainable approach to managing them, you can try maintaining a barrier of clean, bare soil around your home, i.e. free of grass and leaves. Clover mites generally do not cross such a barrier. This barrier should be about 18 to 24 inches wide. If you do have annuals, perennials, or shrubs planted in this zone, have them far enough apart so the clover mites cannot easily bridge across this barrier. Landscape rock is not enough of a deterrent to keep clover mites away from buildings.
2008, Revised 2017