Maine Forest Service: Winter Moth Invasive Found in Harpswell

Maine Forest Service: Winter Moth Invasive Found in Harpswell


Augusta, Maine - A new invasive pest has been discovered in Harpswell, one that can damage Maine's hard wood, fruit trees and blueberry bushes and possibly affect the state's associated industries from wood products to agriculture to tourism, according to Maine Forest Service (MFS) entomologists.

An area of about 400 acres in the small coastal town was found last month to be infested with winter moth, a small tan moth that lays eggs that develop into a voracious caterpillar that causes the leaves on trees to look like Swiss cheese. The green inchworms can be seen in trees this time of year, according to the forestry entomologists. It is the first time that the insect infestation has been found in Maine.

While the state's entomologists have a plan to deal with the winter moth, this latest invasive find nonetheless brings home the same message surrounding all invasive species that threaten Maine's natural resources: Don't move it; whether it's firewood or landscape plants,

"Please leave your hostas at home - it's a really important message," warned Charlene Donahue, MFS entomologist under the Maine Department of Conservation, who discovered the winter moth infestation. "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 moth, which is native to Europe, first arrived in North American in the 1930s in Nova Scotia, where it was a serious problem before being controlled by parasitic flies. More recently, it has been found in the eastern section of Massachusetts for the past 20 years, and it is spreading into Rhode Island and Connecticut.

The insect gets its name because the male moths appear in the late fall and early winter months. Female moths, which don't have wings, lay eggs on the trunks and branches of trees. Those eggs hatch in the springtime into hungry inchworms that feed on the buds and entire leaves of trees, Donahue explained. They also produce silken threads that can carry them on the wind, a dispersal method called "ballooning." After the inchworms get about an inch long, they pupate, or form a cocoon, in June and spend all summer and fall in the ground.

"That is why it important to not move plants from areas infested with winter moth," said Donahue.

The inchworms attach themselves to the leaves of a large number of tree species, including oaks, maples, elm, ash, birch, apple, crabapple, cherry and blueberry. The invasive insect can kill trees by causing defoliation and weakening over a number of years. Other stressors, such as another type of insect, a disease or a drought, then can add to tree mortality, Donahue said.

"In Massachusetts, they are now seeing a lot of tree mortality across tens of thousands of acres," she said.

Massachusetts had a "huge moth flight last winter," Donahue said. Last December, the MFS received a call from a landowner in Harpswell who "wondered what she was seeing." The landowner sent in moths to the MFS, which in turn sent them to Massachusetts for DNA testing. They came back as winter moth.

What wasn't certain, however, was whether there were any female moths around or these were just the male moths from the big moth flight. Donahue went back to the town, and on May 18, she found the inchworms eating in the local trees, indicating there was a full infestation.

The MFS entomologist thinks the winter moths got to the area most likely on landscape plants moved from Massachusetts, as eggs on trees or as cocoons in soil around plants. The winter moth is not regulated in Massachusetts, and there currently is no quarantine in place in the area.

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 rearing and releasing the same fly in Massachusetts and hope that it will soon be at high enough numbers to reduce the winter moth populations there to manageable levels.

The Maine Forest Service is working with the UMass researchers to establish the same control agents in the Maine infestation before it gets much bigger. As currently planned, Maine will be receiving parasitic flies from the UMass colony next year, Donahue said.

"We have found this invasive insect relatively quickly due to an alert landowner," Donahue said. "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."

For more information about the winter moth, go to: http://www.maine.gov/doc/mfs/InvasiveThreats.htm#wm

Or: http://www.mass.gov/dcr/news/winter_moth.pdf

For more information about the Maine Forest Service, go to: http://maineforestservice.org