Itch mites continue to thrive, infuriate

Nearly microscopic oak leaf itch mites are pestering Kansans again this year. Because outbreaks do not occur every year, there is still much unknown about the tiny pests. Photo courtesy of James Kalisch, University of Nebraska-Lincoln.

By Randall Kowalik
K-State Research and Extension

MANHATTAN, Kan. — For the second consecutive year, the tiny pest known as the oak leaf itch mite has driven many Kansans to rub and scratch for days.

The nearly invisible mite is found in home landscapes, windbreaks and anywhere pin oak trees are planted. They fall from the branches, landing on anything under the branches – including pets and humans.

“Basically, what happens when these mites drop down is they get on the shoulders, the heads of people, and they just start biting,” said Raymond Cloyd, entomology professor at Kansas State University. “They’re not transmitting any diseases. They’re just [having] a natural reaction to falling into something that’s unknown to them. So it’s more of a nuisance than anything.”

The biggest challenge with itch mites is how little we really know about them. To study an insect or mite, the problem has to occur on an annual basis – not sporadically. However, this is the first time that oak leaf itch mites have occurred in Kansas in back-to-back years (2015 and 2016).

“We’ve only had four big outbreaks of oak leaf itch mites: 2004, 2009, 2015 and 2016,” said Cloyd, who is a K-State Research and Extension specialist on outbreaks in Kansas. “This again is the first time the mite has been a problem in back-to-back years. We still have a lot more questions than answers.”

The oak leaf itch mite gets its name from the intense itching discomfort it causes in people. The rash that often develops may have more to do with constant scratching than the pest itself.

“People start scratching, so then there are these scratch marks,” Cloyd said. “If they continue to scratch, they can open up wounds that may result in a bacterial infection. I know it can be difficult to stop scratching, but if you don’t, you can make matters even worse.”

The oak leaf itch mite is thought to be exclusive to pin oak trees, though Cloyd acknowledged there is still much research to be done.

“If you don’t have any pin oaks on your property, it does reduce the prospects of encountering mites,” he said. “But again, we don’t know if other gall formers are actually serving as hosts.”

“For example, cicada eggs – the oak leaf itch mite will feed on cicada eggs and so this mite may not be as specific as we as we think it is. In fact, it might be more of a generalist feeder.”

A small midge, or fly, causes raised areas of plant tissue known as marginal oak leaf fold galls. The galls themselves are not harmful to the health of the tree – but oak leaf itch mites love to feed on the larvae of these gall formers. Eventually, the mites fall to the ground or on anything under the tree including humans and pets. Cloyd said pets could be an unwitting source of infestation.

“The pets go outside, and either get underneath a pin oak, or get into pin oak leaves on the ground,” he said. “When the pets come inside the house, they snuggle with their humans and pass on the itch mites.”

Once the mites have found a human host, the itching and associated rash can go on as long as two weeks.

Cloyd said there are ways to reduce your risk of contracting oak leaf itch mites. “It’s easy to tell people to just avoid pin oak trees from midsummer, until all the leaves drop off, but that’s not very realistic. So if you’re going outside to rake leaves, wear long sleeves, long pants, a hat and rubber gloves. Bathe yourself and wash your clothes as soon as you’re done.”

Keeping pets clean and groomed is another way to reduce the risk of contracting oak leaf itch mites, Cloyd said

Some Kansans are looking expectantly toward the first hard freeze to eradicate the oak leaf itch mite population. Cloyd said that’s not a safe bet.

“Insects and mites are a lot smarter than people think,” he added. “A hard freeze is not always harmful to them because they have means of overwintering. What we really need is an extended period of cold weather to lower the soil temperature where the oak leaf itch mites may be located.

“But a hard freeze followed by two or three days of unusually warm weather? They’re going to come back up.”


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