When North Royalton resident Norma Fink got out of the shower Tuesday, she noticed a big welt on her shin with a pimple-like bump in the middle.
She’d noticed some other welts a few days earlier, but nothing this large. Concerned, she headed to an urgent care center.
The culprits, she discovered, had probably been hiding in her pin oak tree.
Fink had been bitten by oak tree itch mites, insects so small they’re nearly invisible to the naked eye. For reasons that aren’t entirely clear, they’ve been making themselves a particularly nagging pest of late in Northeast Ohio.
The mites cause large, intensely itchy welts that look like chigger bites but are usually on the neck, face, arms and upper body, according to the Illinois Department of Public Health. A pimple-like lesion usually forms after about 12 hours, and the welts can last for up to two weeks.
Normally the mites feed on other soft-bodied insects or insect eggs, and they especially like the midge larvae that hatch on pin oak leaves this time of year. But when the maturing midges drop off the trees and leave the mites with nothing else to eat, the mites can turn their attention to other food sources — and that includes us, said Dave Shetlar, an entomologist at Ohio State University.
Shetlar said the mites’ mouths have tiny pincers they use to pierce their prey. They regurgitate digestive enzymes to break down the tissue, and that’s what can cause the itchy reaction, he said.
The mites are so tiny that the wind can blow them through the openings in window screens and even some loose-weave clothing. You probably won’t even know you’ve been bitten until a welt appears.
Oak leaf itch mites — also called oak leaf gall mites — were first recorded in the United States about 12 years ago in Kansas, but Shetlar says it’s possible they were always around but just not recognized.
Why they’re a big problem this year is a bit of a mystery.
Some have speculated that their population exploded this summer because they were well-fed from eating the nymphs of 17-year cicadas. But Shetlar said research hasn’t proved that theory, and he’s skeptical.
Virtually all the cicada nymphs had hatched by about three weeks ago, he said, so that food source would have dried up long ago — long, at least, when compared to an oak leaf itch mite’s brief life cycle. So if the mites were to drop off trees because their cicada food source had disappeared, that would already have happened.
Shetlar thinks a more likely explanation is the growth of bike and hike trails in shady areas, which puts more people than ever in the mites’ vicinity. He noted that when the Cincinnati area had an outbreak a few years ago, the vast majority of people who complained of bites were bicyclists.
Fink, the North Royalton resident, suspects she was bitten when she was trimming shrubs Saturday, but she realizes it could have happened anytime. “Who knows? I could have gotten it after when I was sitting on the porch,” she said.
Insect repellents aren’t always effective on oak leaf itch mites, because the itty-bitty insects don’t fly to a food source but rather bite whatever they happen to land on.
The good news, though, is that the mites typically need about four hours on your body before they can bite through your skin. So after you’ve been outdoors around pin oaks or their fallen leaves, Shetlar recommends taking a shower and tossing your clothes into the dryer on medium heat for 15 minutes or so. The soap and the dryer heat will kill the mites, he said.
Mary Beth Breckenridge can be reached at 330-996-3756 or mbrecken@thebeaconjournal.com. You can also become a fan on Facebook at www.facebook.com/MBBreckABJ, follow her on Twitter @MBBreckABJ and read her blog at www.ohio.com/blogs/mary-beth.