Clover mites, Bryobia praetiosa, are crawling around in homes, apartments, and office buildings. They can invade buildings in large numbers. Clover mites typically invade from the sunny side of a building, the south or southwest exposure. They are primarily a nuisance pest, as they don’t bite humans, but leave a red stain when accidentally crushed.
Adult clover mites are a little larger than a pinhead, red in color, with disproportionately long, pink front legs. They feed on over 200 kinds of plants, including clover, grasses, ivy, honeysuckle, apple, and elm. Clover mites tend to build up in large numbers in heavily fertilized turfgrass. High numbers result in the turfgrass appearing silvery or frosty.
Manage clover mites by (1) avoiding grass near building foundations; (2) placing an 18- to 36-inch-wide band of mulch around the foundation; (3) mowing or trimming grass as short as possible; (4) not overfertilizing turfgrass located near building foundations; (5) removing any weeds growing near the foundation of a building; (6) removing ivy or other host plants from around the foundation and walls; (7) using foundation plants that are not attractive to clover mites—such as marigold, petunia, geranium, arborvitae, and yew; and (8) caulking or sealing cracks in the foundation. Mites found indoors can be vacuumed up; however, be careful not to crush them. Soapy water kills them on contact. Perimeter treatments of chlorpyrifos (Dursban), diazinon, or any of several pyrethroid-class insecticides can also provide short-term relief. Treat a band of soil or vegetation 6 to 10 feet out from the foundation.