High in the trees, as soon as the first leaf buds begin to open in the early spring, browntail moth caterpillars emerge from their winter nests. The larvae voraciously feed on the young leaves with a particular appetite for hardwood species, including oak and apple. 

A heavily infested tree can contain more than 1,000 nests, each home to upward of 400 hungry young caterpillars.

While large infestations can cause serious harm — or even mortality — to the host trees, it’s the small toxic, barbed hairs on the caterpillar’s body that are of the utmost concern for public health, said Eleanor Groden, a professor of entomology in the School of Biology and Ecology at the University of Maine.

The tiny hairs can induce painful poison ivy-like rashes and serious respiratory distress in those who come into contact with them, according to a news release from UMaine. The irritating urticating hairs detach from the growing caterpillars and become airborne as they molt, settling on line-drying clothing, backyard picnic tables and patio furniture, and the ground surrounding the infested trees. Once in the environment, the hairs can retain their toxicity for three years.

In some cases, just being outside in a heavily infested area imparts a risk for being affected, said Groden. 

Groden’s research is focused on understanding the natural enemies of the browntail moth — the various parasitoids, fungi and viruses that target the caterpillars, and may be used to help curb the rapidly expanding moth populations affecting Maine’s communities.

UMaine’s research is part of a larger initiative, one in collaboration with Charlene Donahue, an entomologist with the Maine Forest Service, as well as a growing network of concerned citizen groups who seek to monitor and identify new infestations and develop pest management strategies in areas experiencing an outbreak. 

“One of the things about this insect that makes it challenging to develop a research program is that right now, it’s not impacting anyone outside of the state of Maine. That makes it more challenging to get the resources to work on this project,” said Groden. 

“But because members of the community are willing and motivated to help in our project, it has helped us be able to address some of the issues with our research.”

The browntail moth is an invasive species that was introduced into northeastern North America in the late 1800s when it rapidly spread throughout New England before the populations collapsed in the 1920s and 30s. For decades their population was largely isolated to the tip of Cape Cod and a few islands in Casco Bay. In the 1990s small outbreaks began appearing at mainland sites in Maine’s Midcoast. 

In the past several years, the population and range of the browntail moth has grown significantly. In 2005, more than 24,000 acres in Maine exhibited defoliation due to the caterpillars. Last fall, that number increased to nearly 64,000 acres with new outbreaks appearing in new areas of the state, said Groden.

“We’re seeing an expansion of this insect that we haven’t seen in over 100 years,” said Groden. 

The epicenter of the browntail moth epidemic has been largely centered around Merrymeeting Bay in Maine’s central and Midcoast regions, said Groden; however, new infestations are being identified throughout the state, including recent ones in Burnham and Eddington, and adult moths have been captured from southern Maine to far Downeast Maine, as well as areas farther inland in Millinocket.

“I have a picture of a pupating browntail moth on a child’s stroller, so they get moved around inadvertently by people traveling through the infested areas,” said Groden 

“It’s very possible that the infestations we have now in Burnham and Eddington may have resulted in pupae being moved into the area rather than moth flight.” 

A single moth can lay up to 400 eggs. Without preventative measures outbreaks can spread quickly and many people who live in areas not historically affected by the insect may not know how to identify signs of an outbreak. 

According to the Maine Forest Service, in 2016, areas in the towns of Bowdoinham and Topsham were particularly hard hit. The issue prompted local citizens to organize and form the Bowdoinham Browntail Moth Task Force. Their mission is to educate homeowners and community members about the browntail moth and effective ways to help mitigate their population. The group works closely with members of the Maine Forest Service and researchers from UMaine. 

Groden and Kate Cutko, the library director of the Bowdoinham Public Library, are task force members. 

One of the most effective methods of control for homeowners is to prune the caterpillars' web-like nests from the trees during the winter when they are most visible.

“When we learned that people could clip the winter nests out of the low trees in their yard, the library went ahead and purchased a 16-foot pole pruner that could be borrowed by patrons, said Cutko.

The task force also produced a short video on clipping the winter nests and hosts regional informational meetings at the library. They also created Midcoast Maine Browntail Moth Support, a social media group which helps disseminate browntail moth information throughout the state. 

“To be able to have [Groden] and [Donahue] on speed dial is a gift,” said Cutko. [Groden] is one of the few people studying this problem and her research is vital to giving people hope that we will see the cycle, we will get to the other side of our daily life in Bowdoinham.” 

Cutko said that many citizens in the area are helping to support and facilitate her research in any way they can, from sending her pictures of browntail moth activity to providing her access to infested trees on their property. 

“We need to have community support to address this issue because many of the areas impacted by this insect are private landowners. Their interest and willingness to support this project is what has enabled us to conduct our sampling program and help us identify areas we can monitor,” says Groden. 

“Like all good public libraries we spread information,” said Cutko, “and when we’re lucky enough to have University of Maine scientists feeding us the latest information, it’s a great collaboration.”

For more information about identification and management of browntail moths visit the Maine Forest Service’s browntail moth informational webpage. 

http://www.maine.gov/dacf/mfs/forest_health/invasive_threats/browntail_moth_info.htm

http://www.maine.gov/dacf/mfs/forest_health/insects/browntail_moth.htm

http://www.maine.gov/dacf/php/gotpests/bugs/browntail-moth.htm

People can  call the Maine Forest Service at 207-287-2431 or the UMaine Cooperative Extension: Insect Pests, Ticks and Plant Diseases office at 207.581.3880 for help identifying moths or to report any sightings.