December through March is prime time to start clipping the webs of browntail moths, the pesky creatures that shed poison hairs as caterpillars and cause painful rashes for people.
It is a timeframe when the moths, clustered in the white webs they weave at the tips of branches, lie protected until spring, when they emerge as brown caterpillars with orange dots near their rear end. It is a good time to kill them before they can do damage, experts with the Maine Forest Service and Maine Department of Agriculture, Conservation and Forestry told about 75 attendees in a forest health webinar on Monday.
In addition to stressing trees by eating leaves, the moths also are a health threat to humans, causing painful rashes to those that either brush against them or are within proximity for the wind to blow the poison hairs onto them. The moths were in every New England state in 1914, but now are limited to Maine, coastal New Hampshire and coastal Massachusetts, according to Brittany Schappach, entomologist with the Maine Forest Service.
Containing them is a major focus of the forest service, and that includes cutting moth webs with drones, injecting trees with insecticides, using professional tree trimmers, or having people cut them down themselves. Do-it-yourselfers need some basic information, she said.
“You need to destroy them after you clip them,” Schappach said.
The moth webs can be destroyed by burning them in a contained fire or soaking them in soapy water for three days. She suggested wearing protective clothing, including eyewear, when cutting out webs. Oak, apple, crabapple, cherry, birch and other hardwoods are especially susceptible to moth infestations.
The moths defoliated about 46,726 acres of forests, primarily along coastal Maine, in 2023. That number dropped to 2,119 acres in 2024. Penobscot county saw 19,193 damaged acres in 2023, but that fell to 805 acres in 2024, Shappach said.
The sharp drop can be attributed to several events. The big reason is weather related. The spring of 2024 had a series of rain storms with some drying spells in between, ideal conditions for the fungi and viruses to grow that kill the caterpillars, Schappach said. The steady rains in 2023 were not as conducive to fungi and viruses growth.
Additionally, the state set up a $150,000 moth mitigation fund in 2024. Fourteen towns and organizations received the money. The Coastal Maine Botanical Gardens created informative plaques about the moths that it posted throughout its trails.
In Pownal, fifth-graders collaborated with the town to create “Not wanted!” posters and organized clipping parties to remove the winter webs around the downtown. The fifth-grade classes in the town plan to continue running the project, Schappach said.
“Some towns now have rentable pole pruners for residents to clip the moth webs,” she said. “Even removing a few webs is helpful, because one winter web contains from 25 to 400 caterpillars.”
Environment reporter Lori Valigra may be reached at [email protected]. Support for this reporting is provided by the Unity Foundation, a fund at the Maine Community Foundation, and donations by BDN readers.
