Outdoors

This lake association successfully eradicated invasive Eurasian watermilfoil. Here’s how they did it

Photo Courtesy Invasive Species Centre

As soon as the ice goes out this year, volunteers of the Farlain Lake Community Association will jump in their boats for what has become an annual hunt. The prey? An invasive green lake monster intent on territorial expansion. If all goes well, they won’t find a thing.

Farlain Lake, in the Township of Tiny, Ont., is the poster child for success in the battle against Eurasian watermilfoil.

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“You name the type of eradication method, and we used it,” says Brian Kelso, a member of the FLCA and the head of the Eurasian Watermilfoil Committee, describing the group’s roughly 10-year battle with EWM. Volunteers mobilized in boats to hand-pull the weeds. They laid sun-blocking benthic mats on the lake bottom. They built their own DASH (diver-assisted suction harvesting) system. They installed a containment curtain around the work areas to capture harvested weeds, then volunteers kayaked the heavy remnants back to shore. They even briefly tried Reward, a non-selective herbicide that slowed down the weeds but didn’t kill them. “Ultimately, we were fighting a losing battle,” says Brian.

The game changer came in May 2023, when Health Canada approved use of ProcellaCOR FX, a herbicide that targets EWM without harming native plants. Farlain was the first freshwater lake in Canada where ProcellaCOR FX was used following its approval. Application by a licensed professional took less than a day at targeted sites.

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“Within days, you could see the change, and within weeks, the weeds weren’t even visible in some locations,” says Brian. Even some cottagers who had been skeptical about using an herbicide are now elated to see healthy, native plants growing in formerly infested sites.

Among their proudest achievements in the long saga, says Elizabeth Di Chiara, the past president of the FLCA, were raising funds—$80,000 locally and $200,000 through an Ontario Trillium Foundation grant—and building relationships with various levels of government as they sought permits for the work. “Since our success, close to 50 other organizations have contacted us for advice. It’s so satisfying to see what we’ve accomplished. And so much of it was purely volunteers; it was our own members of the community.”

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This article was originally published in the June/July 2025 issue of Cottage Life.

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