BATH — While other parts of the country gear up for an invasion of “murder hornets,” state officials are asking Mainers to stay wary of a more familiar foe: the browntail moth caterpillar.

As temperatures start to rise, more Mainers are turning to outdoor recreation and yard maintenance. At the same time, the caterpillars are starting to emerge from their webs in trees, according to the Maine Department of Health and Human Services.

Department officials are urging the public to take precautions. The dark brown, fuzzy caterpillars can be identified by their white stripes and red and orange dots. Though they may look harmless, those fuzzy little hairs are toxic and, when shed, release into the air and can cause a skin reaction similar to poison ivy and breathing trouble if inhaled. The caterpillars also can cause serious damage through defoliation.

A browntail moth caterpillar Maine CDC photo

The risk of exposure remains high from now through July, according to DHHS. The hairs can land anywhere, including on trees, in gardens, on lawns and decks. They remain toxic for up to three years.

All counties in southern, Down East and south-central Maine are at some risk of exposure, but the caterpillars have proven in recent years to be a particular nuisance in the Midcoast.

The region seems to have the “perfect atmosphere for them,” Dennis Wilson, Brunswick town arborist said. “Everything came together for this to be the most optimal place for them to be.”

The caterpillars are notoriously difficult to get rid of, as they have no natural predator, leaving humans with the task of reducing the population.

Jarrod Hawkes, owner of Hawkes Tree Service in Phippsburg, uses tree trunk injections and sprays pesticides to protect the trees and kill the insects. People at home can clip nests out of trees and put them into a bucket of soapy water to kill them, he suggested.

He has seen the numbers in Bath, Brunswick and Topsham declining the past few years — a good sign for his business, as he has lost a few employees over the past few years. Some have suffered bad rashes, and one employee was only on the job for three days before respiratory problems forced him to leave.

According to Angela Mech, assistant professor of forest entomology at the University of Maine, there is evidence that cool, wet spring seasons promote the growth of a fungus that naturally attacks the insect and can cause localized population crashes.

“The mortality of a large number of caterpillars means a reduction in the number of toxic hairs in that area compared to areas that still have actively feeding caterpillars,” she said in an email.

“On a separate note,” she added, “wet weather may help to minimize contact with the toxic hairs by reducing the chance that they become airborne.”

Tom Schmeelk, a forest entomologist at the Maine Department of Agriculture, Conservation and Forestry, said that so far, this year has been rainy enough that it might help keep the caterpillars at bay.

“If we continue to have rainy days like we’ve been having, we could be looking at another outbreak of the fungus, which would provide some relief,” he said.

It’s still too early to know exactly how prevalent the fungus may be this year, but a good indication of how problematic the browntail moth caterpillars will be is to look at the number of overwintering webs in the area – the more webs in an area, the higher the risk, Mech said. The Maine Forest Service conducts winter web surveys every winter and creates a map identifying the level of risk by town.

For low-risk towns, according to the map, “webs were frequently encountered, or patches of trees with webs were found.” In “moderate risk” areas, “defoliation was mapped and/or continuous stretches of overwintering webs were found.” For “high risk towns,” defoliation was again mapped and continuous stretches of high populations of the winter webs were found.

Brunswick has been considered “high risk” for the last several years, Wilson said, but this year, was downgraded to “moderate.”

Topsham, Freeport, Pownal and Durham were also rated as moderate, while Bath, which has also struggled with the caterpillars in recent years and was rated as high risk in 2019, moved all the way down to “low risk.” Cumberland, Woolwich and Wiscasset were rated high risk.

To Wilson, Brunswick’s lower rating is an encouraging sign that the management strategies are working. During the winter, when the moths are dormant, the department cuts down the cocoons whenever possible, and in the warmer months they use controlled pesticide spraying, particularly concentrated around heavily trafficked areas like the schools, ball fields, the town mall and the bike path.

He has been monitoring the trees for the last month or so and said he plans to file an application with the planning board to do controls again this year. Last year the town spent $9,070 on browntail moth management and budgeted $20,905 for this year. The numbers include projected costs for spraying, injections and tree pruning, though it is uncertain how much of the money will be spent.

Despite a lower risk than previous years, Wilson urged residents to stay educated and remain vigilant, especially with more people spending time outside due to the pandemic.

Topsham resident Regina Cole knows all too well the havoc the bugs can wreak.

“We live on the outskirts of Topsham and we were swarmed by them last year,” she said in an email. “They covered our house and attacked the garage. It’d swear there were a thousand. It was awful.”

She filled a shop vac with soapy water and for two weeks she vacuumed them off the house, driveway, flagpole, “anywhere and everywhere,” sometimes up to three times per day.

“I have asthma and did not want to have to leave our windows closed all summer,” she said. “I’d get rashes on windy or breezy days and raking in certain areas this past fall would cause a rash.”

Already she can see some nests swinging at the top of the oak trees in her yard.

“I’m not looking forward to them hatching,” she said.

Luckily for Cole, Topsham officials predict a milder season.

“Because of the cold wet spring, we have seen a reduction in the nests this year,” Pam LeDuc, director of the Topsham Parks and Recreation Department said.

The situation is “ever-evolving,” of course, and she is assessing the situation.

The browntail moths have been a lower priority this year than in recent ones, as resources have turned toward COVID-19.

The only treatment they applied was on the recreation fields, where participants were at risk of exposure. The treatment costs roughly $1,000.

“Fortunately that was the one time we needed to use it,” she said.

In Bath, city arborist Kyle Rosenberg is also warning people to be on the lookout for the bugs, even if the risk is considered low.

“Earlier in the season we gave people a heads up to check their trees with nests,” he said. “If they can reach the nests, we told them to cut them out.” He described the nests as looking like “tufted tissue paper.”

Now that the caterpillars are nearing the end of their development, they can apply pesticides to the trees, either through spraying or injection.

The more common host trees seem to be oak, apple, cherry and white birch, Rosenberg said.

“If those trees aren’t in high-use areas, avoid going near them.”

For further protection, DHHS recommends choosing damp days to perform outdoor activities or wetting vegetation with a hose, covering faces with respirators or cloth face coverings and goggles, wearing long sleeves, pants and a hat, taking cool showers and changing clothes after being in infested areas and drying laundry inside during June and July to avoid hairs embedding into clothing.

More information about browntail moths can be found on the Maine Department of Agriculture, Conservation and Forestry website.

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