Emmanuel Wiley, 2, swims Sunday as his mother, Kirsten Petrie, watches from the dock at their house on Jug Stream in Monmouth. A form of variable-leaf milfoil has spread from Annabessacook Lake to the stream, which feeds into Cobbossee Lake. Staff photo by Andy Molloy

MONMOUTH — A long-standing milfoil infestation is spreading downstream from Annabessacook Lake, but treatment might make future removal efforts more effective.

On June 12, a survey team from the Friends of the Cobbossee Watershed found variable-leaf milfoil growing in Jug Stream, which connects Annabessacook Lake and Cobbossee Lake, and removal began 10 days later.

John McPhedran, a biologist with the Invasive Aquatic Species Program at the Maine Department of Environmental Protection, said there are 22 bodies of water in Maine known to have variable-leaf milfoil.

Friends of the Cobbossee Watershed and other volunteers, working with the Maine DEP, removed 385 gallons of the invasive plants during cleanup efforts July 2 and July 9.

Toni Pied, director of development & membership at Friends of the Cobbossee Watershed, said her group, along with the Cobbossee Watershed District, Annabessacook Lake Improvement Association and Maine DEP, have been working since 2014 to combat the variable-leaf milfoil infestation in Annabessacook Lake, which covers 1,420 acres in Winthrop and Monmouth.

“That started as a rapid-response project, and it has quickly gotten out of hand,” she said. “We’ve really not been able to get ahead of it.”


Variable-leaf milfoil is an invasive species in Maine, but grows in other New England states, according to state environmental data. It grows very rapidly and reproduces quickly, Pied said.

“You only need a tiny fragment of the stem to reproduce a new plant,” she said. “It breaks up into little pieces at the end of its life cycle, and each of those little pieces can grow a new plant.”

Recreational activities, including swimming, kayaking and boating, can disturb the milfoil fragments and spread them across a body of water.

Pied said her group worked with town officials to close a boat landing and placed yellow buoys in areas known to have milfoil.

Pied said milfoil can damage water quality and choke out native plants, which affects the food chain for fish and other animals.

Officials also said poor water quality can also affect property values.


Joel Wiley, a Monmouth resident with 500 feet of frontage on Jug Stream, said Sunday he would like to help stop the spread of milfoil to protect the “beautiful area” around his family home, which he bought from his parents about five years ago.

“I would definitely change my shoreline to help stop the spread,” he said, adding he was reluctant to do so because of state shoreland zoning rules. “We should be briefed from the (state) Department of Environmental Protection on what to do.”

Men fish Sunday from the dam at the confluence of Annabessacook Lake and Jug Stream in Monmouth. A form of variable-leaf milfoil has spread from the lake and into the stream, which feeds into Lake Cobbossee. Staff photo by Andy Molloy

Wiley said he and his family, who use the stream every day for recreational activity, are deeply concerned about the environment ramifications of milfoil.

Pied said Sunday residents have options for what they can do to help control milfoil. These include steering clear of areas known to have milfoil — including those marked with buoys — and making sure boat propellors are not spinning when moving through plants.

Pied said residents should also learn to identify milfoil and report any growth to Friends of the Cobbossee Watershed or other appropriate organizations.

Pied said residents can also help fight the spread of milfoil by planting buffer crops on their property to help prevent nutrients from entering bodies of water.


Representatives of the Friends of the Cobbossee Watershed and the Maine DEP are planning to treat Annabessacook Lake next Monday with an herbicide. McPhedran said an airboat will drop the herbicide in an effort to reduce the milfoil infestation.

Pied said the treatment will be the first of its kind in Maine, where environmental officials are more cautious than in other states. She said the goal is to reduce the infestation to help make manual removal of milfoil more effective.

McPhedran said the Maine DEP “does not treat the use of herbicide lightly.” He said the department is using florpyrauxifen-benzyl, which he said has “a very low risk of impact for negative effects.”

“We don’t talk about any of these products as being safe. Everything is in the realm of relative risk,” he said. “We are required to take water samples to run for the concentration of the chemical, and required to continue sampling until the chemical is at a level that’s not detectable.”

The Maine DEP has recommended people not use Annabessacook Lake water for irrigation until the chemical dissipates.

And while there is no recommendation from the U.S. Environmental Protection Agency against swimming in water treated with florpyrauxifen-benzyl, environmental officials in Maine advise against swimming or boating Aug. 17 in the treatment areas.

In 2019, the same herbicide was used to combat Eurasian watermilfoil in Cobbossee Lake, which was found in 2018.

McPhedran said it was too early to tell if the species has been eradicated from Cobbossee Lake, but initial tests have been encouraging.

He said it would take several years of testing before officials know if eradication efforts were successful.

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