WINTER MOTH CATERPILLARS, which have been detected in Harpswell, devour hardwood and fruit trees, posing a risk to two key Maine industries. The Maine Forest Service said it is attempting to contain the winter moth’s spread and as part of that effort has urged residents not to move any firewood or landscape plants.
An area of about 400 acres in the coastal Cumberland County town was found last month to be infested with winter moth, according to entomologists. The small, tan winter moth lays eggs that develop into a voracious caterpillar that can make leaves on trees look like Swiss cheese. It previously has not been found in Maine.
The Maine Forest Service said it is attempting to contain the winter moth’s spread and as part of that effort has urged residents not to move any firewood or landscape plants.
“Please leave your hostas at home; it’s a really important message,” said Charlene Donahue, an entomologist with the forest service and Maine Department of Conservation who discovered the infestation in Harpswell. “We’re warning people not to move plants out of Harpswell or from Massachusetts to Maine, because you might bring the problem with you.”
Winter moths, native to Europe, first arrived in North America in the 1930s in Nova Scotia, where the infestation posed a serious problem before being controlled by parasitic flies, according to a press release. In the past 20 years, it has been found in the eastern section of Massachusetts and also has spread to Rhode Island and Connecticut.
The insect gets its name because the male moths appear in late fall and early winter months. Female moths, which don’t have wings, lay eggs on the trunks of trees. The eggs hatch in the spring into hungry inchworms that feed on the buds and entire leaves of trees. They also produce silken threads that can carry them on the wind through a dispersal method called “ballooning.”
After the worms grow to an inch long, usually in June, they form a cocoon and spend all summer and fall in the ground.
“That’s why it is important to not move plants from areas infested with winter moth,” said Donahue.
The inchworms attach themselves to oak, maple, elm, ash, birch, apple, crabapple, cherry and blueberry plants. They can kill trees through defoliation over a number of years.
“In Massachusetts, they are now seeing a lot of tree mortality across tens of thousands of acres,” said Donahue.
The moths were discovered last December by a Harpswell landowner who sent specimens to the Maine Forest Service. Their DNA tested positive as being winter moth, but entomologists were unsure until this year that the moths were males from a large moth flight last year in Massachusetts. Donahue confirmed on May 18 that winter moth inchworms had infested the area in Harpswell.
The Maine Forest Service says the winter moths likely came to Maine on landscape plants from Massachusetts as eggs or as cocoons in the soil around transported plants.
A parasitic fly that was released in Nova Scotia helps keep the winter moth population under control there. Researchers at the University of Massachusetts, Amherst, are releasing the same fly in that state in an attempt to control the moths. The Maine Forest Service is working with UMass in an effort to bring the flies to Maine next year.
“We have found this invasive insect relatively quickly due to an alert landowner,” said Donahue. “Hopefully, by using the flies as bio-control agents, we will be able to get the problem under control quickly and it will not spread further.”
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