Clover Mites

Printer Friendly Version

Clover mites (Bryobia praetiosa) are not insects but rather are more closely related to spiders and ticks. They are tiny, about ¹/₃₀ inch (0.85 millimeter) in length. They vary in color from rusty red to greenish with orange-red markings. The adults are eight-legged. Their distinctive front legs, which can be observed with a magnifying lens, are almost twice as long as their other legs and extend forward near the head in a manner similar to antennae.

Clover mites live and reproduce outdoors. Those that find their way indoors will not reproduce and will die within a few days. Outdoors, they feed on many kinds of plants that grow around structures, including clover, grasses and ornamentals. They prefer lawns that are heavily fertilized. When many mites are present they can cause areas of a lawn to appear bronze.

Clover mite numbers are usually greatest in the spring and fall when daytime temperatures are below 70 °F. At these times they often migrate into structures by mistake. They gain entrance through small cracks and crevices around doors and windows. They are harmless and do not bite people or pets. However, their sheer numbers can be an annoyance, and they can stain fabrics or walls if crushed. The red spots that remain when clover mites are squashed aid in identification of the mite.

Female clover mites lay unfertilized eggs; male clover mites are unknown. The eggs are bright red and spherical. Clover mites prefer cool temperatures and lay eggs to survive the heat of summer as well as freezing winter temperatures. These eggs are laid under loose pieces of bark or in cracks and crevices in the walls of buildings. The summer eggs hatch when temperatures cool in the fall. The winter eggs hatch very early in the spring.

During mild winters, all developmental stages of this pest may be present. These stages include the egg, larva (immature stage), two nymphal stages (immature stages) and adult. The larvae that hatch from the eggs are bright red and six-legged. The nymphs are eight-legged like the adults. The length of time required for the completion of one life cycle is approximately one month.

Clover mite control is usually not difficult. If possible, remove grasses, weeds and fallen leaves in an 18- to 24-inch band around the foundation of the infested structure. Clover mites do not readily cross bare, cultivated soil. Areas cleared of grass can be replanted with plants that are not appealing to clover mites, such as marigold, zinnia, rose, chrysanthemum, petunia or shrubs like spruce and juniper. They should be planted in such a way as not to provide a bridge for the mites to cross from the lawn to the building. While bare soil provides the best barrier to clover mites, if mulch is considered essential, washed gravel or stone is preferable to organic materials such as bark or pine needles.

Cracks and crevices that allow mites to enter the building should be caulked and sealed. If mites do enter, they can be vacuumed using a soft brush attachment to avoid crushing them. Once vacuumed, place the bag in outside trash.

Pesticides are not recommended for clover mites unless the temporary annoyance becomes intolerable. Sprays should be applied to outdoor areas where the insects or mites enter the structure or collect in large numbers. If large numbers of insects are killed, be sure to remove them. Dead insects, especially in wall voids, can attract more serious pests. If treating plants or the house exterior, make sure the product you use will not damage them and is labeled for the area and pest you are spraying. Remember, seasonal pests may come from areas outside of your property that you cannot spray.