By Whitney Cranshaw, Colorado State University Cooperative Extension, Entomology
Clover mites as lawn and household pests are usually a late winter/early spring phenomenon. The mites, which develop on grasses and various plants around the foundations of homes, periodically enter buildings in large nuisance numbers. "Walking dust specks" is a frequent description of these nuisance invaders, and they leave a rusty smear when crushed.
Developing clover mites are located in a fairly restricted area of the yard/landscape. This is because clover mites use such vertical surfaces to molt and lay eggs. Warmer, sun-exposed aspects are particularly used by clover mites, which thrive in the dry conditions present in these areas.
During early to midspring, clover mites also may damage turfgrass around building foundations and in other warm, dry areas of a lawn. Feeding damage appears as small, meandering silver streaks (stippling) in the leaves. When mite populations are high, leaves may be extensively injured and die. Areas of grass within 5-10 feet of a building, tree, shrub or other upright object may be totally killed, appearing as light brown, irregular dead patches.
Clover mite injury to turf is commonly mistaken for winter kill and usually is found in the same sunny, dry areas of the lawn where winter drying problems occur.
This year is looking to be well above-average for clover mites. This is due in part to the drop in temperature experienced with the snow/frost last September. The cooler temperatures are important in the hatching of eggs. Clover mites "oversummer" as eggs, becoming dormant when temperatures warm. An early fall storm allows the mites a longer period to develop in the fall, perhaps producing an additional generation. Furthermore, at least along the Front Range, this has been a generally warm, dry and open winter - all conditions that favor population increases of the mites.
The best cultural control of clover mites is to try a little winter watering in those sites where the mites thrive - at the south and west sides of buildings. This can greatly retard populations increasing in spring.
Kelthane, applied to lawn areas where the mites breed and to the base of foundations, is recommended for clover mite control.
Photographs of clover mite damage courtesy of Judy Sedbrook.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010