Maine Forest Service provides moth-control strategy

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Harpswell — Little worms are causing big problems in town, but those problems can be controlled.

Since it was discovered last winter, the winter moth has damaged at least 400 acres on Harpswell Neck, Orr’s Island and Vinalhaven, said Charlene Donahue, an entomologist with the Maine Forest Service.

She said that although the moth was seen last winter, it has likely been here for longer.

“They’ve been here for some time because of the amount of acreage that’s already affected and how severe it is in some places,” she said. “Low levels of damage was noted by arborists last year but trees always have small holes in the leaves and they didn’t think anything of it because it could have been any native insect.”

The moth, which Donahue said came to Maine from Massachusetts, where it has damaged tens of thousands of acres, is in cocoons in the soil from June through October and only emerges in the late fall and early winter.

“If you bring any plants (to Maine) that come out of your yard or nurseries in the infested area that have soil on them and have been outside, there is a good chance there are winter moths (in the soil),” she said.

The female moths, which don’t have wings or fly, lay their eggs on the trunks and branches of trees. When the eggs hatch in the spring the small worms feed on the buds and entire leaves of trees. Adding to the problem, the worms produce silk threads that catch the wind and allow them to travel.

“They strip the trees so completely that if there’s another moth that comes along and gets the next set of leaves, that can really do a tree in,” said Harpswell resident Robert McIntyre. “Trees normally can put out a new set of leaves but if that new set is taken away then you’re in real trouble.”

At an informational meeting on Wednesday night, Donahue showed residents the best methods for controlling the pests.

“If the infestation is not too heavy, and in a lot of places in Harpswell and Vinalhaven it’s not, in the fall people can put bands around the trees in their yards and then put sticky on them so that the females can’t get up the trees to lay their eggs,” she said.

In addition to wrapping trees, Donahue recommends spraying trees with horticultural oil in the very early spring to suffocate the eggs and then treating the tree with a bacterial insecticide.

She said that now that the moth is here, residents should be focused on controlling them because complete elimination is unlikely.

“It’s a matter of controlling them and reducing the spread,” she said.

For the long term, the Maine Forest Service is looking into the possibility of bringing in a fly parasite that has been used successfully in Massachusetts as a way to control the moth population. The only problem is that the fly takes several years to be established.

“If people are having defoliation right now, they may want to take some of those other steps,” she said.

Amber Cronin can be reached at [email protected] or 781-3661 ext. 125. Follow her on Twitter @croninamber.