FALMOUTH — A state expert has seen a local decline in browntail moths this year by about half, crediting spraying and a damaging fungus in part for the decrease. As a result, Falmouth residents may have fewer allergic reactions to moth hairs this summer.

A close up of browntail moth caterpillars on a tree. The larvae have toxic hairs that can cause rashes and difficulty breathing, according to the Maine Forest Service. Courtesy

Thomas Schmeelk, an entomologist at the Maine Department of Agriculture, Conservation and Forestry, said between the local effort and about 50% fewer nests that could be attributed to a fungus, Falmouth will see some relief.

The town just wrapped up a week-long program to spray nests on Friday that covered 24 widely traveled, high-risk roads. High-risk areas have six to eight nests per tree, or are areas with multiple trees with six or more nests along or in a public way. Included were Route 1, Johnson Road, Northbrook Road, Foreside Road, Waits Landing Road, Old Mill Road, Town Landing Road and Knight Street.

“(Spraying) can reduce people’s likelihood of contact with the hairs, in a playground or even outside of a post office, for example, and reduces the number of caterpillars hitchhiking on someone’s car to a new area,” Schmeelk said.

Despite the reduction in the browntail population, Falmouth residents are considered at a moderate risk of exposure to the moths, according to the state risk map, which is calculated by the number of nests and notable damage to foliage. To the north, Cumberland is deemed high risk.

“We saw about half as many winter webs this winter (as last year) … ,” Schmeelk said.

Schmeelk said the decrease is possibly due to a potentially fatal fungus called  entomophaga aulicae, but comparative populations aren’t known.

“It’s difficult to quantify due to a few factors, including limited aerial surveys due to aircraft availability last year,” said Schmeelk. “I wouldn’t feel comfortable stating a percentage, but the fungal outbreaks last spring-summer have dropped (populations) in (the Falmouth) area by a great deal, possibly by half.” 

He believes the fungus is prevalent now due to the cold, wet climate last spring. 

“I’m not seeing as many active webs; there were some new, fresh webs, but not as many active caterpillars,” Schmeelk said. “I think many nests have failed, possibly due to the fungus. I haven’t been able to suss that out.

The invasive browntail moth entered the U.S. in the 1890s from Europe, according to the Maine Department of Agriculture, Conservation and Forestry.

The caterpillar has two patches of orange on one end, and toxic microscopic hairs to deter predators. The hairs can cause a blistery rash and respiratory distress when inhaled.

The caterpillars are active in mid-April through June and August through early October, when they nest and hibernate, respectively, according to the Maine DA CF.

“Public health and the environment are big for us, we don’t spray over flowering plants or around pollinators, and it’s a targeted chemical for the browntail moths, and they don’t do it in high winds or rain,” Town Manager Nathan Poore said.

The state assesses the moth population yearly with two aerial surveys to map damage to foliage from the caterpillars and moths, as well as a foot survey in the winter.

Poore noted that spraying helps reduce exposure, but infestations on private property can harbor the moths.

“If you think you have a problem, contact the local tree service companies,” Poore said. “However, once they are moths it’s too late. For those who missed the timeline, there are things you can do to improve living with the situation.”

On the town website, it’s recommended that residents dry laundry indoors and take a cold shower and change clothes after outdoor activities. It also suggested that homeowners do yard work in coveralls, use goggles and a respirator, and work outside when it’s rainy or damp.

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