Herbicide eases milfoil’s stranglehold on Lake Iroquois

View of Lake Iroquois from the shore

Lake Iroquois has seen a decrease in invasive milfoil this summer after an herbicide was applied to the water in June. OBSERVER PHOTO BY JASON STARR

‘The effect has been profound’


Observer staff

It was just days after a chemical herbicide was applied to the north end of Lake Iroquois in Williston that the targeted invasive water weed, Eurasian milfoil, began to recede.

The treatment, sponsored by lakefront homeowners (the Lake Iroquois Association) and the municipal Lake Iroquois Recreation District, with representatives from each of the lake’s surrounding towns — Williston, Richmond, Hinesburg and St. George — took place June 28. By mid-July, milfoil, which for years had clogged the waters around the public beach and boat launch, was nearly eradicated, according to Lake Iroquois Association vice president Chris Conant. For the rest of the summer, boaters and swimmers were recreating like it was the 1980s, before the milfoil took hold, he said.

“The effect has been profound,” Lake Iroquois Association president Shannon Kelly said. Conant resides on the north end of the lake, near the Vermont Fish and Wildlife Department boat ramp and the Lake Iroquois Recreation District beach. He has heard positive feedback from users of both facilities.

“For the first time in a long time, you can take a kayak or a canoe and go out in the middle of that lake and look down and see the bottom of the lake,” said Conant. “We have not have that pleasure for many, many years, and it’s pretty amazing how awesome that looks.”

The association had tried other methods of milfoil eradication in years past, hiring divers to hand-pull the weed and placing mats on the lake bottom to cover it. A permit application with the Vermont Department of Environmental Conservation to use the chemical Sonar was denied in 2018 after a group of Hinesburg residents — with backing from the anti-chemical advocacy group the Toxics Action Center — flooded state regulators with concerns.

The state approved the association’s request to use the chemical Procellacor in Lake Iroquois in April, over the objections of the opposing Hinesburg residents.

A total of 20 gallons was poured into about 36 acres of the lake. The lake’s surface area totals about 245 acres. Signs around the lake advised against swimming for 24 hours after the chemical was applied. According to Conant, the chemical caused no lasting damage to any other plant species.

On Monday, a lake health specialist is scheduled to conduct a plant survey of the lake, raking up plant life from the bottom and determining what species are present. The survey is required by the association’s herbicide permit and Conant expects it to confirm the success of the herbicide treatment.

“It’s pretty amazing to have that much success with such a safe and minimal amount of chemical applied to the water,” he said. “This is a great step in the right direction. We feel really good about it. And we’re looking forward to getting the quality and health of the lake back to where it was 30 years ago.”

Conant hopes the association’s board of directors will agree to apply the chemical in another part of the lake next season. That would require an additional approval from the state Department of Environmental Conservation.

“We will eventually be doing another treatment at some point,” Conant said. “We have the rest of the lake to take care of. We can’t just do one end and not the other. It’s going to start all over again if we’re not careful.”