The invasive browntail moth, which has hunkered down in the midcoast for years, is expanding into Portland and its northern and western suburbs, bringing thousands of new, unsuspecting Mainers into contact with the caterpillars’ toxic hairs.

In Yarmouth, town employees have posted signs and roped off areas infested with browntail moth caterpillars to protect residents from exposure to the hairs that cause a blistery, itchy rash similar to poison ivy. Browntail moths have been found in nearly every Yarmouth neighborhood and have left some oak trees nearly bare of leaves. Bruce Maasbyll said he feels trapped in his Yarmouth home after repeatedly getting itchy rashes and watching caterpillars nearly strip his 60-foot oak trees of leaves.

“They munched them bare from top to bottom in a couple weeks,” he said. “One night I had gone out on my deck to have a beer and relax. The next morning I woke up with a really hot, burning rash all over my neck, chest and back.”

The Department of Agriculture, Conservation and Forestry last week warned people to use extreme caution when removing cocoons from trees to avoid exposing themselves to the toxic hairs in the cocoons.

Browntail moths are found at varying population densities over more than 6,500 square miles in Maine and in recent years have been most highly concentrated in Brunswick, Bath and Topsham. But the high-risk exposure area has expanded as far west as Turner, south to Falmouth and east to Jefferson, according to state forestry officials.

“Browntail moth is not new in those areas, but it is intensifying,” said Allison Kanoti, a forest entomologist with the Maine Forest Service.

Small numbers of webs also have been found in Portland and surrounding suburbs that in past summers were considered free of the pest.

Patches of webs have been spotted in Gorham and Standish, areas that previously had a lower risk of exposure to browntail moths.

Browntail moth caterpillars have microscopic hairs that break off the caterpillars and circulate in the air. The dried skin that the caterpillars release when molting also contains the hairs. Skin contact with the hairs can cause a blistery, oozy rash. Some people also experience respiratory distress after inhaling the hairs into their lungs.

The hairs are most abundant from May through July when the caterpillars – which have two telltale red dots on their back ends – are in a feeding frenzy before they change into moths in August.

Now in its end-stage caterpillar form, the pests are munching on tender leaves of apple, oak and other trees.

The itchy rash caused by browntail moth hairs has brought hundreds of people to local pharmacies in Portland and Brunswick for lotions and sprays made specifically to treat browntail moth exposure.

At Coastal Pharmacy and Wellness in Portland, more than 450 prescriptions for the treatment have been filled since May, including 96 in one day alone.

Many of those prescriptions are for residents of Falmouth, Cumberland Foreside, Yarmouth and Freeport, said Kim Crabb, marketing director for Coastal Pharmacy and Wellness.

Signs at the Yarmouth High School tennis courts warn of browntail moths. The town doesn’t spray pesticides on public property but uses acephate insecticide on trees near the North Road playground, library and high school.

“We have been inundated,” she said. “People will come walking in the door lifting up their shirts and itching. People standing in line commiserate with each other. People are very frustrated and obviously very uncomfortable.”

Karyn MacNeill, director of Yarmouth Community Services, said browntail moths are not new to Yarmouth, but this year is different.

“For lack of a better term, it’s exploded in Yarmouth,” she said. “This year we’ve seen it scattered through almost every neighborhood in town.”

Town employees have had to rope off areas where people congregate – including around the high school tennis courts – to protect residents from exposure to the moths. The town does not spray pesticides or insecticides on public property, but did inject acephate insecticide into the root crowns of trees near the North Road playground, library and high school.

MacNeill said the town also stepped up its educational campaign by hosting a meeting for residents, posting information and resources on the town website, and hanging signs about browntail moths in areas that have been treated or roped off.

A browntail moth’s nest, pictured in Bowdoinham, is filled with larva. The caterpillars recently were concentrated in Brunswick, Bath and Topsham. Now high-risk exposure areas have expanded as far west as Turner, south to Falmouth and east to Jefferson. One Portland pharmacy has filled more than 450 prescriptions for treatment since May.

Maasbyll, the Yarmouth resident, said he would like to see the town do even more to address the issue. With the moths spread throughout town and the hairs blowing in the air, a few signs aren’t enough, he said.

“You can’t address this just by saying every man for themselves,” he said. “This is a public health problem. It’s a quality of life problem. It’s everybody’s problem.”

Browntail moth infestations can be difficult to deal with because of restrictions on using pesticides in certain coastal areas.

Forestry officials recommend people check their oak and apple trees for moth webs in the fall. They should clip out any webs they can reach, then burn them or submerge them in water. If the webs are too high to reach, a licensed pesticide applicator can treat them in the spring.

People who live in areas affected by the moths should take extra precautions to protect themselves, especially during dry weather when the microscopic hairs are more likely to be circulating. People can wear long pants and sleeves when they mow their laws – or mow when the grass is wet – and avoid sitting under apple and oak trees that show damage from the moths.

The Department of Agriculture, Conservation and Forestry has more information about the moths on its website, along with a form where people can report the presence of browntail moths.

Gillian Graham can be contacted at 791-6315 or at:

ggraham@pressherald.com

Twitter: grahamgillian