State rejects herbicide use on Lake Iroquois milfoil

A popular herbicide will not be used on Lake Iroquois to control an influx of Eurasian milfoil after the state of Vermont recently rejected a request by the Lake Iroquois Association and the town of Williston.

In a decision dated Oct. 8, the Vermont Department of Environmental Conservation rejected a permit for the use of an herbicide product called Sonar to rid the entire lake of the invasive plant.

Users of Lake Iroquois likely have noticed a large growth of Eurasian milfoil in recent years. The invasive species covers about 67 percent of the lake’s area where plants can grow, according to a 2014 study of lake by the Lake Iroquois Association.

The association and the town of Williston developed a strategic plan for mitigating the invasion.

The Vermont Department of Environmental Conservation however rejected a permit application saying that Williston and the Lake Iroquois Association cannot use Sonar on the lake. The town and environmental group applied for the state permit in 2016, working with the department to analyze treatment options for the lake.

“We understand the use of herbicides is controversial, but we feel it is safe,” said Jamie Carroll, secretary of the Lake Iroquois Association. “We didn’t come to this decision lightly. We will continue research to control the infestation.”

The herbicide has been deemed safe for use in waters used for recreation, and drinking and it’s been used in lakes in Vermont to treat milfoil, and in drinking-water reservoirs around the country, Carroll said.

Another group interested in the lake and the permit application is the Concerned Citizens of Lake Iroquois who opposed the use of Sonar.

The local group worked with Toxics Action Center, a public health and environmental nonprofit that has been working with residents in Hinesburg. In a news release after the state permit rejection, the Toxic Action Center praised the move saying: “The decision sets a precedent that could impact pesticide use statewide.”

Without the use of Sonar, the Lake Iroquois Association is using more localized methods of removing the milfoil.

Earlier this summer the association hired a group to perform diver-assisted suction harvesting in the lake. The group spent three weeks removing milfoil by the rock island at the middle of the lake. It would take the divers another four to six weeks to remove all the milfoil in the are around the rock island, Carroll said.

Harvesting “is effective, but the operator has to be very careful” to remove only milfoil, Carroll said. He added it is expensive to have humans manually doing the labor.

The association “is trying to be equitable to landowners and people who recreate in the area,” Carroll said. “That is what was attractive about Sonar – the whole lake approach.”

In addition to physically pulling out existing milfoil plants, the Lake Iroquois Association has tried some prevention strategies to curb the spread of the plants. The association and town of Williston have put in place a greeter program that allows people to check boats for invasive species. The association has also worked on stream remediation which protects the lake from pollutants which allow the invasive species to thrive and bottom barriers that protect from invasive species coming in on the bottoms of boats.

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