The Maine Department of Environmental Protection plans to use herbicides to kill invasive variable leaf milfoil infestations on three Maine lakes this summer.
The agency is seeking new permits to apply chemicals in Messalonskee, Little Sebago and Androscoggin lakes, according to a department notice.
John McPhedran, an aquatic invasives specialist at the department said it used the herbicide ProcellaCOR against milfoil infestations several times since the product was authorized by federal regulators in 2017.
"What we're doing is we are discharging a pollutant to the state water, which none of us really like to do," McPhedran said.
"But we feel there are certain instances when it is warranted, and these are instances which we think that it is warranted," McPhedran added.
Chemical treatments are effective at killing invasive milfoils, McPhedran added. Although treatment also harms native plants, they have recovered quickly after previous treatments he added.
However, Maine is not considering widespread chemical treatment against invasives, McPhedran said. The state's priority remains to tackle infestations by mechanical means, such as pulling plants out by hand or with the assistance of boat-borne vacuums. There are nearly 40 Maine lakes with known invasive plants according to a 2024 department count.
"No matter how successful you are with applying an herbicide, there has to be continued work from here on out to try and manage these aquatic invasive plants," McPhedran added.
The state plans to target a fresh outbreak on 23 acres on Androscoggin Lake, near Wayne, where McPhedran said there is a chance to eradicate the plants.
It is also hoping to treat a 4-acre patch on Little Sebago Lake that is separate and isolated from a longstanding infestation. On Messalonskee, which also has some extensive invasive growth, the department wants to apply herbicide on 18 acres to prevent further spread in the lake and to other water bodies.
Lidie Robbins, executive director of the 30 Mile River Watershed Association in Wayne said the organization fully supports treating the outbreak in Androscoggin Lake.
"Everyone I have talked to has been supportive of it," Robbins said. "People don't take it lightly, but this particular herbicide is known to be quite safe and does not have lasting impacts."
Maine DEP is the only organization in the state authorized to use herbicides on water invasives. However, it still needs to secure environmental permits for new applications, according to McPhedran. The state also plans to treat invasives on Northeast Pond in Lebanon under an existing permit, he added.
The department will hold public meetings about its plans on June 3 in Belgrade, June 8 in Wayne and June 24 in Windham.
It proposes to apply chemicals between July and August.
