December 8, 2012

Winter moth sightings could signal trouble for Maine trees

By North Cairn
Staff Writer

The winter moth, which has caused widespread damage already in southern New England, has moved into eight more communities since populations were first discovered in Maine a year ago.

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The winter moth is a pest that strips trees of their leaves and ultimately kills them, and is a serious problem spreading into Maine from southern New England.

Maine Sunday Telegram photo by Bo Zaremba

State officials, concerned that the moths might be spreading even farther around the state, are asking residents to watch for the drab, light brown, tan or gray moths.

In its larval stage, the winter moth can denude trees, eating the leaves and ultimately weakening them enough so that a secondary stressor such as drought or disease can debilitate and kill them.

A limited number of moths, only males, were spotted initially along the Maine coast in 2006 by entomologist Joe Elkinton, a professor at the University of Massachusetts at Amherst. The moth remained very limited in the state -- until now.

It was found in Harpswell in December 2011, and in Vinalhaven in the spring of 2012; but over the past few days, a spate of sightings occurred in Cape Elizabeth, said Charlene Donahue, forest entomologist with the state Department of Agriculture, Conservation and Forestry.

In 2006, no females of the species, Operophtera brumata, had been detected in traps in Maine, and no defoliations had been found, so the moth was not considered a problem here. The first full populations of moths weren't found until 2011, and only in one coastal community, Harpswell.

The sudden increase in reported swarms has been unexpected, and officials are trying to monitor where the moths are flying.

"It is unusual," Donahue said. A state alert about the moths was issued Tuesday and by midday Wednesday, Donahue already had received reports of 13 sightings of moths flying in Cape Elizabeth, as well as scattered reports from Scarborough, South Portland, Portland, Falmouth, Woolwich, Westport Island and Brunswick.

Winter moths, which are believed to have been introduced into North America from Europe, were found in Nova Scotia as early as the 1930s. They have become a serious problem in Massachusetts over the past several years, particularly in coastal communities south of Boston and on Cape Cod.

The potential economic effect of a winter moth infestation in Maine is difficult to estimate, Donahue said. It strikes several species of trees and shrubs here, including oak, maple, apple, elm, ash, crabapple, cherry and blueberry.

In Massachusetts, Elkinton said, no damage estimates have been determined in terms of forests, crops or home landscapes; but the pest has been particularly destructive in blueberry fields, and to a lesser extent in apple orchards that haven't been sprayed with insecticides.

Donahue said homeowners are likely to face increased costs for prevention and treatment of vulnerable plantings, as well as dealing with trees that might die over several years.

Another recent pest, the emerald ash borer, posed a threat to the 6.7 million cords of ash harvested in Maine each year, with a value of $140 million annually. That figure does not represent a major component of Maine forests, said Kenneth Lawtsen, biometrician for the Maine Forest Service.

By comparison, winter moths pose a vastly more significant potential threat because they can affect all hardwoods, not just a single species, he said.

Elkinton said the moths have remained almost exclusively "a coastal phenomenon." What's still unknown is how warm weather trends may affect their ability to spread. Usually, the moths cling to the coasts, where temperatures are more moderate; but if interior parts of the state remain temperate enough, the moths may move inland.

"I don't think it's a threat to much of Maine," Elkinton said, "but it is spreading."

The moths are an unfamiliar threat for now.

"I don't even know what it is," said Gordon Waterman, of Sanford, chairman of the New England Apple Association, based in Hatfield, Mass. "I talk to a lot of growers" all over New England, he said, "and I haven't heard of it. Maybe I'm living under a rock."

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