Garden Tips: Clover mites a nuisance in the home

Marianne C. Ophardt, WSU Benton County ExtensionMay 23, 2014 

During some years, certain insect populations will generate concern with a sudden increase in numbers. This spring, one such creature is the clover mite.

Technically, this large mite is not an insect. It is an arachnid and is more closely related to spiders, ticks and scorpions. As a group, arachnids have eight legs, no wings and two body sections. Adult insects have six legs, three body sections, and most also have wings.

These mites are visible, being just a little smaller than a pin head. Their body pigmentation is bright brick red, turning to a reddish brown as they age. They have eight legs, but at first glance, the front legs look like antennae because they are longer than their other legs.

Clover mites feed by sucking plant juices from the leaves of grass and clover, but they also feed on low-growing ornamental plants. They do not bite humans or other animals.

The plant damage caused by their feeding is characterized by stippling or meandering silver streaks in leaves. It is usually not severe enough to harm a plant or even noticed by gardeners. However, the mites can become a nuisance when they enter homes: They cause a reddish stain when crushed.

Clover mites spend the cold winter and hot summer months in the egg stage. They hatch in the spring and fall when temperatures are between 70 and 85 degrees. Then they feed on plants and proceed through three stages of growth before becoming egg-laying adults. There are multiple generations each year.

In the fall, clover mites try to find a protected spot to spend the winter. This cozy spot may be somewhere outdoors or within the outside home walls. When looking for an spot, some mites may accidentally enter the house. In spring, when the sun warms outside walls, especially south- and east-facing sides, the overwintering mites can become active and accidentally come inside. Clover mite invasions are usually most severe when grass and weeds are allowed to grow close to a building, especially where the grass is lush and heavily fertilized.

Indoors, clover mite control is best accomplished using a vacuum or wiping them carefully with soapy water and a sponge. On the outside, simply squirt them off with soapy water. Any of the insecticidal soaps should work well, but make sure whatever you use does not stain the finish.

To prevent future outbreaks, consider not allowing grass to grow next to the foundation by creating a 2-foot or more deep landscape bed around the home. To help with weed control, mulch this grass-free zone with a 3- to 4-inch layer of bark or pea gravel. You may also want to make the bed deeper and plant it with ornamental shrubs and flowers.

It is also a good idea to tighten up your home by caulking outside cracks and crevices. This is helpful in preventing clover mites, spiders and other pesky insects -- and non-insects from becoming a nuisance indoors.

-- Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.

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