Sam Trafton, of Maine Drone Imaging, sends a drone up from the steps of Waterville City Hall Thursday to check the status of browntail moth nests in Ellie, the elm tree in Castonguay Square. Photo courtesy of Thomas Klepach

Much of central Maine is expected to dodge the brunt of browntail moth troubles this year after apparently successful mitigation efforts around Waterville and Augusta the past few years.

Waterville has been aggressively tracking and treating trees on city property for browntail moth over the past few years by contracting with a company to clip nests from trees, insert treatment plugs or inserts into trees and spray them with an organic substance that is not harmful to humans. Thomas Klepach, a Colby College assistant professor and Waterville city councilor, went out Friday morning with Sam Trafton of Maine Drone Imaging to look for and photograph browntail nests on various city-owned land, particularly where people congregate.

“We found just a few nests at Head of Falls, there’s nothing at North Street and just a few in the old elm tree in front of City Hall,” Klepach said. “At the junior high, we found several trees directly adjacent to the fields. We used the drones and we kind of did a survey.”

The data will be sent to Bartlett Tree Experts, the company the city contracts with, and Bartlett will arrive in early to mid-May, as soon as the caterpillars start to emerge, to spray an organic substance that contains spinosad, according to Klepach. He said the spray is not harmful to humans.

The weather also has cooperated this spring, with showers and cool temperatures, he said. Too much rain, and the fungus that helps to retard browntail gets washed away, he said.

Last week, the Maine Department of Agriculture, Conservation & Forestry issued an online update reporting outbreaks at 10 sites infested with browntail. This year, they are in Bangor, Belfast, Bridgton, Brunswick, Dover-Foxcroft, Hancock, Lincoln, Newport, Turner and Unity.


On April 15 the department got its first report of newly emerged browntail moth caterpillars, according to the update. They will continue to feed on maturing leaves and grow larger through the end of June and, even though caterpillars are small now, their hairs readily break off and can cause rash on humans, according to the site.

Penobscot, Waldo, Knox and Hancock counties had large browntail population increases last year, based on aerial data, according to the department, which notes that if May and June have normal spring rain amounts, the wet season may allow diseases to disrupt browntail population and lead to a collapse.

“However, if we have a dry spring, we are likely to see BTM populations continue to spread and fill in areas of previous collapse. People should not rely on disease-related collapses to save them from the rash.”

The department urges people to avoid infested areas, cover bare skin when working in those areas and try to do yard work on wet days to help reduce stirring hairs while mowing or raking leaves. Web removal should be done ideally in winter and before springtime because after caterpillars emerge the chance of success in treating areas is reduced, according to officials.

Pruning wounds this time of year can be more damaging to trees and shrubs. The department recommends that people wanting to use insecticides to treat browntail work with a licensed pesticide applicator.

Meanwhile, Klepach, in Waterville, has been working with the city to determine which trees need treatment and find more cost-effective and efficient ways of surveying large areas of tree canopy without the need to send people out in the field to inspect each tree.

“The idea is to fly a drone over the tree canopy and then use AI (artificial intelligence) that has been trained to identify the browntail moth winter webs to analyze the footage and provide GPS coordinates and web counts for trees that need treatment,” said Klepach, whose students work on the effort.

He said one way he hopes to improve the capacity of the technology is to use an infra-red camera to help identify the nests. Caterpillars cluster together in winter webs to protect themselves from the bitter cold, but that thermal benefit may also provide an improved way to identify active webs, Klepach said. It can also help locate difficult-to-see nests that are high in the trees, he said. The browntail effort is being conducted in collaboration with the Davis Institute for AI at Colby.

Klepach recommends people turn off outdoor lights between 10 p.m. and 2 a.m. for three to four weeks in July to help keep browntail moths away, as they are attracted to light. If people do need outdoor lights, he said, he recommends they use warmer color lights – yellow-shifted as opposed to blue-shifted lights.

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