Southern Maine

Anticipated Moth Infestation Hampered by Fungus

Before Maine met some unseasonably wet weather at the end of May, state officials prepared themselves for more than 10 thousand acres of tree defoliation by caterpillars.

Who knew caterpillars could cause so much harm?

In fact, Browntail moths cause more damage as caterpillars than as adults—and their damage capabilities extend beyond plants. As they mature, browntails leave behind hair and dander containing toxins that can cause asthmatic reactions in humans.

Although 11 days of rain ultimately deterred the Browntail moths from causing further damage in the Brunswick area, the pest prevailed to attack the city of Portland.

If left untreated for a sufficient amount of time, “a Browntail infestation could eventually kill an oak tree,” said Kevin Bosworth, local tree service professional and district manager of the Davey Tree office in Portland.

Dr. Stephen Sears, Maine state epidemiologist, shares advice and precautions in the Maine Public Broadcasting Network story about Browntail moth infestations.

For more information, read the story below or see it on The Maine Public Broadcasting Network.

Anticipated Moth Infestation Hampered by Fungus

By Tom Porter, The Maine Public Broadcasting Network

Earlier this year, public health officials were warning people in the mid-coast communities of Bath, Brunswick, Topsham and Bowdoinham to be prepared for an infestation of Browntail moth - a noxious caterpillar whose hairs can cause blisters and skin rashes, as well as respiratory problems, in humans. Surveys carried over the winter found about twice the expected number of moths wintering in the tops of oak trees. The moths are at their most troublesome when still in the caterpillar stage, and the furry Browntail variety are very fond of feasting on oak leaves.

Entomologist Charlene Donahue of the Maine Forest Service says on top of the public health concerns, state officials were braced for more than 10 thousand acres of trees to be defoliated by the CATERPILLARS this year..

But then something happened:

“And then we got 11 days of rain at the end of May.” Said Donahue, “This unseasonably wet and cold spell sent the caterpillars back to their webs where a cold-weather infection took hold. The fungus was killing them. It's called Entomophoga Aulicae.”

As the weather got dryer and warmer, Donahue and her colleagues were finding fewer and fewer Browntail moth caterpillars alive in the Brunswick area. “You could see these yellow halos of spores coming out of their bodies, and we kept on checking day after day, and every day there would be fewer live caterpillars until we just weren't finding any at all in that area.”

Browntail moths may have succumbed to a fungus in the Brunswick area, but drive a few minutes down the coast, towards Portland, and it's a different story.

"About from this point right up the coast there's a good chance that there's infestation .."

Kevin Bosworth drives down a private road towards the ocean in Falmouth Foreside - a leafy, affluent community just minutes from Portland.. He's district manager with Davey Tree Experts in Portland - one of the companies recommended by the state for dealing with Browntail infestation.. He says after about 5 years of inactivity in this area, the moths are back. “If we get out here I can show you some of the damage that it does.” Bosworth points to a tree, half of whose branches have no leaves on them. This is a white oak here, and you see the foliage on either side of it, but in the middle you see how the foliage has been eaten by the brown tails”

Tom Porter: “Yeah, it looks dead.”

“Yeah, and see the little white masses at the top? Those are the nests.” Said Bosworth

The nests he points to are only between 3 and 5 inches in length.. Since the start of May, Bosworth says his company has treated 25 properties in the Falmouth and Freeport area. Typical treatments involve introducing an insecticide into the tree base which works its way up into the leaves, or spraying the leaves directly. If left untreated for long enough, Bosworth says a Browntail infestation could eventually kill an oak tree.

The Browntail moth is an invasive species which arrived in the US from Europe in 1910. Currently the only 2 places in North America where it is found, are on the Maine coast and in Cape Cod.

Maine state epidemiologist Dr Stephen Sears has this advice for anyone living in an area blighted by Browntail moths. “Try to avoid contact with them number one, and number two if they do have contact, to wash it off. Or if they have asthma from it to wear like a respirator or a mask.”

Nor should the residents of the Brunswick-Bath-Topsham area assume they are now free from the effects of the bug, Charlene Donahue of the Maine Forest Service says the creatures may be dead - but their dander lingers: “The hairs don't just go away when the caterpillars do.”

She says the toxins in those hairs can stay active for a year or more: “So people that are living areas that have been infested, needed to remember that. And continue to mow when the grass is damp and we careful about doing any raking or going into brushy areas where those hairs are still active.”