The tell-tale red-orange dots on the back of browntail moth caterpillars make it easy to identify them. Credit: Abigail Curtis / BDN

After sightings in all 16 Maine counties and countless Mainers itching the blistery rash, the worst may be over for the year’s browntail moth caterpillar infestation, experts say.

In April, experts predicted  this summer would be the worst for browntail moth caterpillar infestations since the invasive insect arrived in the state 100 years ago. They were right.

Browntail moth caterpillars have poisonous, irritating hairs that can cause a blistery rash similar to poison ivy. The hairs also can cause respiratory distress if breathed in. The Maine Center for Disease Control and Prevention classifies browntail moth caterpillars as a public health nuisance.

According to Jim Dill, pest management specialist with University of Maine Cooperative Extension, many of the caterpillars have entered the pupa stage inside a silken cocoon. But there are still caterpillars out there. On Tuesday, Dill said state officials had reported the first sightings of browntail moths newly emerged from cocoons in the Hallowell area and in Old Town.

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“The number of calls I’ve been getting from people about the caterpillars has really fallen off in the last week,” Dill said. “From what I have seen and heard, [the caterpillars] were all on the move looking for places to pupate and I expect people are going to be calling me asking what are all these white moths flying around?”

While browntail moths have been an issue along the coast for years, Dill said this is the first summer they have been so numerous inland.

When those moths do emerge, they are going to be attracted to any light at night. Dill said it’s not at all unusual for someone to go to bed having left a light on inside or on the exterior of their house and wake up the next morning with the entire side of their house covered in browntail moths.

“In the mornings the moths have a tendency to stay in place for a while,” Dill said. “You may see birds grabbing them to get a free breakfast.”

This could be a good time to practice some browntail moth remediation, which could help prevent an even larger outbreak next year.

“If you figure it’s a 50-50 ratio of male moths to female moths that means for every two moths you kill, you are killing one female and getting rid of hundreds of future caterpillars,” Dill said. “At the very least you have done what you can to keep as many away from your home as possible.”

Dill recommends picking the moths off wherever they are clustered and dumping them into a bucket of soapy water to kill them. Be sure to wear gloves though. While it’s the caterpillars that have the toxic hairs, the moths could have stray hairs leftover from the caterpillar stage still clinging to them, Dill said. 

It might be tempting to put a bug zapping light outside, but entomologists with the Maine Department of Agriculture, Conservation and Forestry do not recommend using them.

“Those zappers really do more harm than good,” said Tom Schmeelk, forest entomologist with the Maine Forest Service. “Not only do they kill off beneficial bugs, they are going to attract more browntail moths to your yard.”

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Schmeelk also recommends keeping all outdoor lights turned off during the moths’ peak flying time between 9 p.m and midnight if you want to keep them away from your house.

Dill said even though the caterpillars are winding down, it’s still a good idea to hose off any outdoor furniture before using it.

“I have seen a lot of people with that rash on the underside of their arms,” Dill said. “I’m guessing the caterpillars crawled across a picnic table shedding hairs or the hairs drifted down from overhead trees.”

Looking ahead to next year Schmeelk said there is no real way to predict browntail moth caterpillar populations. Much, he said, depends on the weather between now and then.

“If we continue with a drought it’s most likely to be the same as this year,” Schmeelk said. “But if we have a wet May and June we will likely see an outbreak in fungus that attacks and kills the caterpillars.”

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Julia Bayly

Julia Bayly is a reporter at the Bangor Daily News with a regular bi-weekly column. Julia has been a freelance travel writer/photographer since 2000.