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.
Mites in the house are very difficult to control with any of the chemicals that are safe to use in houses. Vacuuming or wiping them up with a damp cloth is probably the simplest way to clean them up. A pyrethrum aerosol bomb will kill those mites hit directly by the spray but will give no residual action. Household insecticides containing chlorpyrifos (Dursban) applied around doors and windows may also help reduce the number of mites in the house.
The best answer to the problem is to prevent the mites from entering the house by spraying the outside walls and the lawn with an effective miticide and to use a barrier of cultivated soil next to the foundation. Mites do not readily cross loose, clean cultivated soil; therefore, a band approximately 1824 inches wide all around the house, kept free of grass, would be an excellent deterrent. For decorative purposes, this strip may be planted to annuals, perennials, or shrubs, but in such a way that mites cannot bridge across the barrier. The soil around such plantings should be kept cultivated-free of grass, weeds, and fallen leaves. Landscape rock will not act as a barrier to clover mites.
There are a number of miticides now available that will help control the clover mite problem. Any one of the sprays recommended here may be applied to the outside walls, foundations, and lawns for at least 25 feet out from and all around the house. Use a drenching spray instead of a mist like spray. The best time to apply the spray is in the fall to prevent the movement of the mites to the house. Spraying should be done during the warmest part of the day when the mites are most active. Spray thoroughly around doors, windows, and foundations. Some spray formulations may slightly discolor dark dark colored finishes. Granules can also be applied in a 5 foot band next to the building foundation.
Use any one of the following:
- diazinon 8 fl. oz. of 25 percent concentrate in 3 gals. water
- diazinon granules 2 or 5 percent
- chlorpyrifos 5.3 percent EC spray (1 tsp. per gallon of water)
- malathion 50 percent EC (2 to 3 tsps. per gallon of water)