Browntail caterpillars are covered with tiny, toxic, barbed hairs that can cause a rash PHOTO COURTESY MAINE FOREST SERVICE, FOREST HEALTH & MONITORING

Hungry, itch-inducing caterpillars take toll on humans, trees

ELLSWORTH — If there is one good thing to say about browntail caterpillar season, it’s that it is wrapping up.

As far as enemies go, this foe is unassuming. But don’t be fooled by its small, fluffy appearance. The caterpillar’s hairs can cause a fierce itch when they land on skin.

“It’s awful — the itch is worse than chicken pox,” says Valerie Folckemer, who encountered the insects at her house on Newbury Neck in Surry.

The caterpillars are brown and can be identified by the two white stripes that run along their backs and by two distinctive orange dots. Their tiny hairs are barbed and toxic.

“I am covered in a severe rash from this stupid caterpillar and have been for an entire week now; it just seems to be getting worse, not better,” said Jill Rothrock of Hancock.

The itching started June 17 when she was running errands in Ellsworth. Her daughter spotted a caterpillar on her shirt.

“I didn’t even look, I just screamed and tried to shake it off my shirt. My daughter screamed and ran away,” Rothrock recalled. A friend plucked the insect off her shirt with a paper towel.

“Then the rash started getting worse. By the time I went to bed, I had what looked like hives on my chest, shoulder and neck.”

The following Monday she went to the doctor, who prescribed a compound for the rash. It didn’t help much.

“My doctor and his nurse said they are getting so many calls about this caterpillar and rashes that it is causing people,” she said.

There is little good to say about browntail caterpillars, according to Tom Schmeelk, a forest entomologist with the Maine Department of Agriculture, Conservation and Forestry.

The species is nonnative, having arrived in the United States from Europe in 1897. By 1904, he said, the caterpillars had established themselves in Maine. They gobble up leaves, damaging trees. Their hairs evolved as a protection against predators, but there are few of those in Maine.

What does keep the population in check — when conditions are right — is a fungus, entomophaga aulicae. The fungus thrives during cool, wet springs. But dry weather this year meant the fungus was only documented in a few places in the state, said Schmeelk.

The heaviest concentration of browntail caterpillars in Maine has been around the Cumberland/Freeport/Yarmouth area, he said, but they’ve “been expanding inland and north over the past four years.”

“Deer Isle, especially Little Deer Isle, has a lot of it,” Schmeelk said.

Ellen Farrin can attest to that. She developed a raised, red rash after a run in with the caterpillars in Little Deer Isle. “I never touched them. It must have been hairs though the air,” she said.

While outside working on her traps, Stonington lobsterman Julie Eaton had one of the caterpillars drop down the front of her shirt. “It was terrible and still is!” said Eaton.

Laura Stewart and her family were covered in welts after encountering the caterpillars in their Franklin yard this year. “Sooo itchy,” she said.

The state conducts aerial population surveys in the late spring/early summer and late summer/early fall looking for signs of deforestation caused by the caterpillars. There is another survey in mid- to late-December to count webs.

The state uses the data to estimate and map the exposure risk for the coming season. The exposure risk map, as well as a FAQ about the caterpillars and other resources are available at

This is not the best time of year to fight an infestation, Schmeelk noted. The caterpillars are fairly large and roaming. Even if a pesticide were used to eradicate the insects, their bodies — and their itch-inducing hairs — would remain. The hairs can remain toxic for up to three years. Wind, mowing, raking, sweeping and leaf blowing can stir up the hairs and cause them to go airborne.

Individuals reactions to the hairs vary, according to the state Center for Disease Control and Prevention (CDC).

“Most affected individuals develop a localized rash that lasts from a few hours to several days,” according to a CDC statement. “In more sensitive individuals, the rash can be severe and last for weeks. Respiratory distress from inhaling the hairs can be serious. The rash and difficulty breathing result from both a chemical reaction to a toxin in the hairs and a physical irritation as the barbed hairs become embedded in the skin and airways.”

But there’s good news. This year’s crop of caterpillars is starting to pupate. That’s when they spin the cocoons in which they will turn into moths. The hairs will remain in the cocoons when the moths emerge, so steer clear. The moths do not cause an itch.

Browntail moths flock around an outdoor light fixture. Only seen in July and August, the moths have white wings and a tuft of dark brown hair on the abdomen.

Using bug zappers to kill the moths so that they cannot reproduce is not effective, according to Schmeelk. The zappers attract a higher percentage of male moths than females. They may also kill off parasitic wasps and flies that can attack browntail caterpillars and help control the population.

For Mainers with outdoor lights, Schmeelk recommends shutting them off at night, especially between 10 p.m. and midnight when the moths are most active. You don’t want to attract more to your yard. The moths lay their eggs in August and the caterpillars that hatch will overwinter in webs.

A good way to stave off next year’s infestation is to look for the webs starting in late December. There are a couple other web-making caterpillars in Maine. The browntail webs are distinctive in that they are never larger than palm-sized, Schmeelk said. The webs usually appear at the very tips of vegetation on new growth and are tightly woven. The caterpillars like oak, apple, crabapple, cherry, shadbush and rugosa rose.

Clip the webbed branches from the trees then burn them or put them in a bucket of soapy water for a couple days. No need to fear the itchy hairs at this stage of development, those usually develop around the time the caterpillars emerge in April. Every web counts, according to Schmeelk.

Each can contain 25 to 400 caterpillars.

Cyndi Wood

Cyndi Wood

Managing Editor
Cyndi is managing editor of The Ellsworth American. The Ellsworth native joined the staff of The American in 2007 as a reporter.
Cyndi Wood

Latest posts by Cyndi Wood (see all)

Leave a Reply

Your email address will not be published.