December 14, 2012

Experts: Destructive winter moths are spreading

Many tree species are potentially imperiled by the pest, reportedly sighted in several coastal Maine communities last week.

By North Cairn
Staff Writer

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The winter moth, like this male example, strips trees of their leaves and can ultimately kill them. The species, which has been spreading into Maine from southern New England, has been spotted in Cape Elizabeth and several other communities this winter, a noticeable increase over last December, when they first were detected. Conservation officials are asking residents to bring samples to state entomologists so they can track the spread and degree of infestation in Maine.

Bo Zaremba photo

Nonetheless, state officials are asking residents to keep an eye out for the moths, which are in their adult phase at this time of year and most likely to be seen flying in swarms ranging from dozens to hundreds, Donahue said. If people think they see a swarm, they are asked to try to capture some specimens.

Adult moths are active from late November to January, whenever the temperature rises above freezing, as it has for several days recently, Donahue said. Males are small, light brown to tan; females small and gray, with smaller wings, incapable of flight.

The moths are drawn to porch lights or lamplight filtered through window or door screens. Or, they may be seen around deciduous trees, where they mate, or crawling at or slightly above the trunk base.

Winter moths are difficult for a lay person to distinguish from similar-looking species, but if you see a swarm of dun-colored moths flying at this time of year, in all probability, they're winter moths.

Winter moths have moved in every direction in and beyond Massachusetts. Their devastation has been felt as far south as Rhode Island, where they have been seen for a decade, and north through New Hampshire into southern and coastal Maine.

Entomologists theorize that the pest arrived here in cocoons buried in the soil of landscape trees and plants from infested parts of other New England states, Donahue said.

Because winter moths pupate in the ground, they can be moved in soil from late May through December. Caterpillars can be spread accidentally on and in cars, boats and even on clothing and boots.

The moths have no natural enemies in North America to keep the populations in check. A parasitic fly, Cyzenis albicans, has been established in six Bay State communities and is showing some effectiveness in controlling the winter moth, Elkinton said.

Any moths that can be caught or trapped should be placed in a plastic bag and delivered for positive identification to Donahue at the Forest Entomologist Insect and Disease Laboratory, 168 State House Station, Augusta 04333. 

Staff Writer North Cairn can be contacted at 791-6325 or at:


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