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State Denies Herbicide Treatment For Invasive Milfoil In Lake Iroquois

A view of Lake Iroquois in Chittenden County, Vermont.
Hunter Hedenberg, Courtesy
Lake Iroquois straddles several Chittenden County towns including Hinesburg, Williston and Richmond. The state has rejected a proposal to treat the lake with a chemical herbicide to control invasive Eurasian watermilfoil.

State environmental officials have rejected a plan to use a powerful chemical herbicide to control an invasive water weed in Lake Iroquois in Chittenden County, saying the potential environmental damage did not justify its use.

The herbicide is called Sonar, and it's used widely to control aquatic plants for both backyard ponds and in larger lakes. However the state says it should not be used to treat all of Lake Iroquois.

Josh Mulhollem, the state’s aquatic invasive species management coordinator, said the Lake Iroquois decision is noteworthy.

“This is the first time, at least in recent memory, where an herbicide application treatment was flatly denied,” he said.

"There were other, less intrusive options other than the whole-lake chemical treatment which was proposed." — Josh Mulhollem, Department of Environmental Conservation

Mullhollem is an environmental scientist and studied the plan to kill Eurasian water milfoil in the 229-acre lake. He said the proposal was rejected because it did not sufficiently consider non-chemical alternatives and could damage native plants along the lakeshore.

“There were other, less intrusive options other than the whole-lake chemical treatment which was proposed,” Mullhollem said.

The herbicide plan was backed by the Lake Iroquois Association, with the town of Williston as the official permit applicant.

The Lake Iroquois Association said the Vermont Department of Environmental Conservation took 693 days to issue its final decision. Association spokesman Jamie Carroll said the volunteer group is considering its next steps.

"The association has been researching ways to control milfoil for a number of years and moving forward with this herbicide seemed like the best approach," Carroll said. "This herbicide has been used in other lakes in the state of Vermont since 2000 to treat Eurasian milfoil, so it does seem like a shift for the state."

Carroll added that the association has tried a number of other measures, including using divers to suction the plants off the bottom and placing barriers in the lake to stop its spread.

"This herbicide has been used in other lakes in the state of Vermont since 2000 to treat Eurasian milfoil, so it does seem like a shift for the state." — Jamie Carroll, Lake Iroquois Association

Elizabeth Deutsch lives near the lake, and she was one of several local residents who worked together to fight the herbicide plan. Deutsch said she is thrilled by the state’s decision because the risks were just too great.

“It isn’t like you go in and you just target the Eurasian milfoil,” she said. “It kills the invasives and the native plants, so any broadleaf plant.”

Shaina Kasper, the Vermont and New Hampshire director of the Toxic Actions Center, grew up near Lake Iroquois and helped Deutsch and others with their campaign against the herbicide plan. She said the state’s decision was welcome.

“This decision really is ground-breaking and sets a good precedent for Vermonters who are standing up for a safe and pesticide-free way to take care of the environment,” Kasper said.

The state’s permit decision notes that invasive milfoil has been in the lake for years and is likely to remain there, no matter what is done.

Deutsch agreed. Her family has a small motorboat and she swims and paddles in the lake. The milfoil can be a problem, she said, especially when the water level is low.

“It’s a little slimy. But ... it's not like the attack of the bog monster where it’s going to wrap around your legs and drag you to the bottom,” she said.

And Mulhollem, the state official who reviewed the permit, said the town and lake association are free to propose a more targeted approach to treat the milfoil in certain areas rather than using herbicide on the whole lake.

John worked for VPR in 2001-2021 as reporter and News Director. Previously, John was a staff writer for the Sunday Times Argus and the Sunday Rutland Herald, responsible for breaking stories and in-depth features on local issues. He has also served as Communications Director for the Vermont Health Care Authority and Bureau Chief for UPI in Montpelier.
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