Just one small piece of Eurasian watermilfoil has the potential to devastate a lake, hurting native plants and animals, dramatically reducing nearby property values, and hindering boaters and swimmers.

In 2018, that plant was found in Cobbossee Lake, also referred to as Cobbosseecontee. Since then, groups like the CYC Lake Association (formerly known as the Cobbosseecontee Yacht Club) and Friends of the Cobbossee Watershed have been working to eliminate the plant.

The 8.7-square-mile lake touches Litchfield, Manchester, Monmouth, West Gardiner and Winthrop. According to the association, the combined value of shoreline property along the lake exceeds $700 million.

The Maine Department of Environmental Protection in 2019 treated the lake with ProsellaCOR, a selective herbicide that only targets invasive plants.

But peace in the lake was brief, as the plant was once again discovered in October 2020 after a plant survey team with the watershed group discovered a significant infestation in the northeast quadrant of the lake.

In late 2021, their survey team found a fragment of the watermilfoil had spread as far down as Farr’s Cove, about halfway down the lake.


“A fragment, or piece of the plant would have only traveled there by boat,” said John Stanek, of the lake association. “On the north end it has spread to two other locations with a serious infestation in Weston Brook which feeds into the northeast corner of the lake.”

And since the problem was rediscovered last  year, Stanek said the association has created a development committee to not only eliminate all the invasive plants in Cobbossee, but to build a model for other lake associations to follow.

To do this, Stanek said they plan to reach out to businesses that depend on the success and garner their support. The association hopes to build membership and increase engagement, continue fundraising to fight infestation, and to reach out to other lake associations to gain a greater understanding of how to fight the watermilfoil.

The lake association has already spoken extensively with the Seven Lake Alliance in Belgrade, the Upper Saranac Lake Association in New York, the board at Lake Dunmore in Vermont, and has studied the success of other lake associations that were successful in eliminating the plant.

“We are modeling particularly after Upper Saranac who have managed their lake successfully for a number of years,” he said. “We have found the other lake associations quite willing to share their knowledge and expertise.”

The association found that lakes of a similar size affected by the plant spent between $200,000 and $400,000 annually to successfully control the infestation.


As of early January, Stanek said the association is in the early stages of a lengthy fundraising campaign. Stanek said some have shown great support already and that the association is actively working with major donors.

Formal announcements regarding this campaign will begin this June, when most lakeside residents return to the area.

Goals for the new year include budgeting over $230,000 for doubling survey capacity, tripling courtesy boat inspection staff, and earmarking $60,000 for plant eradication.

Though the treatment isn’t cheap, the costs are dwarfed by the potential loss in property values.

According to a 2010 study, the presence of Eurasian watermilfoil has the potential to reduce property values by 16%. For the shoreline properties, this means more than $100 million in lost property value.

The association hopes not only to contain the spread within Cobbossee, but to prevent the plant from reaching adjacent lakes.


“We don’t like, in fact we abhor, the idea that our lake is now in the position to contaminate other lakes in Maine and beyond if a fragment leaves on someone’s watercraft.”

The watershed group and lake association met with Winthrop officials last October to explain the issue and request that they come together and brainstorm with officials from the other towns surrounding the lake. Winthrop was receptive, and council chairperson Sarah Fuller said the town’s officials are keeping an eye on the lake.

With support from surrounding towns and lake advocates, Stanek said the association is confident that it can stay ahead of the problem.

“The key is to be aware of the risk, vigilant in inspections and survey work, and have the team and resources ready to respond instantly when something breaks through the safety net,” he said. “We are all volunteers and are working incredible hours, but inspired by the support and commitment and of others and the opportunity we have to keep this lake beautiful if we respond with speed and thoroughness.”

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