2015-06-26 / Front Page

Moth damage subsides in Cape

By Duke Harrington
Staff Writer

CAPE ELIZABETH — A combination of a harsh weather and state pest control efforts have led to a noticeable decline in defoliation in Cape Elizabeth from winter moths, according to a recent report by town tree warden Mike Duddy.

Since 2013, the winter moth, which has decimated thousands of acres in southern New England, has taken up residence in Cape. The pest (scientific name: Operophtera brumata) first arrived in Nova Scotia from Europe in the 1930s, although it was not until 20 years later that it drew notice when defoliation became a widespread problem.

It’s thought the winter moth was carried into Cape Elizabeth by landscapers from away. The concern is that it feeds on the leaves of all hardwood trees and bushes during the month of May, while in its caterpillar form. Targets include oak, maple and apple trees and, more importantly in Maine, blueberry bushes. The result is leaves that emerge from their buds looking like green Swiss cheese, already full of holes. Over time, the constant denuding can leave trees weak enough that they succumb to other diseases and conditions they might ordinarily resist.

However, Duddy says the effects of the moth’s presence arenoticeably less extensive” this year than during the past two summers. Even so, he said, there are parts of the town with at least moderate defoliation, as well as some pockets suffering from complete defoliation.

Duddy pinned this year’s respite on two factors. First, because the actual moth phase of the insect occurs at the end of November and in early December, when it flies about looking for new places to lay its eggs, many were culled by the early onset of harsh weather last year. Cold temperatures and snow during the first week of December helped to reduce the eventual population of the bug in its caterpillar form, Duddy said.

Second, starting in 2013 as soon as the problem was discovered, the Maine Forest Service released thousands of parasitic flies used to successfully combat the winter moth spread in Canada and the northwest United States.

The fly (Cyzenis albicans) lays eggs on leaves that are small enough to be eaten by the moth during its May feeding frenzy. The fly egg then hatches into a maggot that lives in the moth’s throat, escaping harm when it periodically molts its caterpillar skin and gut. Once the moth drops to the ground in June to cocoon in the soil, the fly begins to eat the pupate from the inside out.

“These biocontrol efforts may also be having an effect on the winter moth population in Cape Elizabeth,” Duddy said.

Still, it’s not all good news.

“The winter moth caterpillar usually favors oaks, but will feed on the leaves of a broad range of hardwoods,” Duddy said. “This year, it appears to me that maples have been hit as hard as oaks, and other hardwoods, such as cherries, are being defoliated to an extent not seen in prior years.”

After pillaging the eastern side of Massachusetts, the winter moth spread to Rhode Island, Connecticut and southern New Hampshire. It first began appearing in Maine in 2007. However, the alarm truly sounded in 2011, with a call from a Harpswell homeowner, which alerted forestry officials that the invasion had finally begun in earnest. By the following year, about 400 acres were denuded in Harpswell, according to Charlene Donahue, who is a forest entomologist with the state Department of Conservation, Agriculture and Forestry.

Since then, the moth has been found from Kittery to Bar Harbor, but Cape has become “a real hotspot” for the winter moth, Donahue has said.

In 2013, a Maine Forest Service survey at Two Lights State Park showed 1.3 moth larvae per leaf bud from a sample of 30 buds.

Still, Donahue pointed out that while the winter moth has been in eastern Massachusetts for 18 years, it’s only within the last four that trees have begun to die off.

“People don’t have to panic,” she said. “But it is something we are at least trying to be watchful of. Even if we somehow got a sufficient number of flies for next year, that’s not an immediate solution. It will take four or five years for the flies to acclimate to the environment and catch up to the moth in terms of population, so people will see damage for some time.”

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