Garden Variety: Oak leaf itch mites continue to be a problem

Oak leaf itch mites are again biting northeast Kansas residents who spend time under affected oak trees, leaving itchy and painful red welts on people.

Until freezing temperatures arrive, the best way to avoid being a victim of oak mites is to avoid working or playing under oak trees for extended periods of time, cover bare skin with long sleeves and pants, and, if exposed, shower and wash clothes as soon as possible after exposure.

Oak mite (Latin name Pyemotes herfsi) bites are similar to mosquito or chigger bites, but they tend to appear on shoulders, neck, and chest because they bite in the vicinity of where they land when falling from trees. Oak mites can crawl into loose clothing but rarely make their way to waistbands or socks like chiggers. Oak mite bites may also have a blister in the center of the raised area, generally appear 10 to 16 hours after exposure, and may itch for a week or more.

According to Kansas State University, DEET-based repellents provide mixed results, and spraying oak trees is ineffective because mites begin their life protected inside leaf tissue.

Researchers are working to learn more about oak mites and how people can better protect themselves from them. Until more is known, bathing and washing exposed clothing along with the other tactics mentioned are the best courses of action.

Anti-itch creams and antihistamines are options for relief if bites occur, or consult a physician.

Oak mites were first reported in Kansas in 2004 and 2007. They mostly disappeared until 2014, but are now on their third consecutive year with high populations in the area. Because they are a relatively new problem in this area and insect populations are often cyclical, oak mites could disappear next year or continue their rampage.

Populations of oak mites build very quickly if adequate food is present. A baby mite matures in seven days and flies off or floats away on the breeze and mates. Males then die, but each female finds a food source and quickly produces another 250-plus mites (most of which are also female).

Although the name implies that oak leaf itch mites feed only on oak trees, they are predators of many insect species. They have become most noticeable in association with oak trees because of their feeding on midge larvae that cause oak leaf margin galls, identified by a swelling and deformation of the edges of oak leaves. Female oak leaf itch mites crawl inside galls to feed on the midge larvae and produce offspring. Baby itch mites develop inside the leaf tissue before dropping out to float away on the breeze and continue the cycle.

Oak mites are thought to be native to Europe and may have been accidentally introduced into the U.S. in the 1990s. Outbreaks have also been reported in Illinois, Missouri, Nebraska, Ohio, Oklahoma, Pennsylvania, Tennessee and Texas.

— Jennifer Smith is a former horticulture extension agent for K-State Research and Extension and horticulturist for Lawrence Parks and Recreation. She is the host of “The Garden Show.”