Lake Iroquois' invasive milfoil slows as officials consider herbicide permit
Growth of Lake Iroquois' invasive milfoil appears to have slowed on its own while a permit to kill it is in the hands of state regulators.
Hinesburg residents living near the lake say they observed less growth of Eurasian water milfoil this summer than in the previous year. They have some theories about the reasons behind the change.
The record warm winter of 2015-16, reported by the National Weather Service, allowed plants to overwinter well and get a good start on growth in 2016, Lake Iroquois Association (LIA) member Jamie Carroll said. In contrast, a cloudy, rainy spring in 2017 slowed proliferation of Eurasian milfoil that relies on sunlight to reach its underwater stems and stimulate growth.
More:Cool summer temps stymie cyanobacteria
A similar situation occurred in many of Vermont’s lakes where the invasive milfoil is found, according to Josh Mulhollem, Environmental Scientist specializing in aquatic invasive species management for the Vermont Agency of Natural Resources.
Its growth can be quite variable from year to year in all lakes, but recent advances in control can be partially attributed to lakeside homeowners’ improving their septic systems, erosion control and public education about milfoil, Muhollem said.
After the invasive milfoil entered Lake Iroquois about 1990, likely from the exterior of boats that had picked it up in other lakes, it outpaced native water plants and spread to cover 70 acres of the lake’s 244 acres.
Efforts to control it included an application to the Vermont Department of Environmental Conservation for a permit to apply the herbicide Sonar in 2017. Although the department issued a draft of the five-year permit to the Town of Williston, acting as agent for the LIA, it did not issue a final permit after reviewing comments, both pro and con, from residents. It's potential approval is unknown at this time.
Hinesburg resident Roger Donegan said he disapproved of the herbicide's use. He believed it would impact wildlife in the natural areas near his home between Lake Iroquois and Lake Sunset.
“We see muskrats, great blue herons, black ducks, beavers, cattails and arrowhead plants. There is life on the lake,” he said. “Do we want a black empty lake or do we want life on the lake?”
Jamie Carroll, of the LIA, said the permit, if granted, would be useful for milfoil control in the future and could tip the balance in favor of native plants.
Other methods used in the lake included hot-water pressure washing of boats entering the lake, training of greeters to inform boaters about milfoil, and diver-assisted suction harvesting.
Lake Dunmore and Lake Morey groups have used an herbicide that acts specifically on Eurasian water milfoil.
Don Weaver, chairman of the Lake Morey Commission, said the herbicide Renovate was applied in 2007, with an exciting result. Invasive milfoil was reduced from 65 percent of lake vegetation to 7 percent in 2015 and 1 percent in 2016. Suction harvesting, where a diver hand pulls the entire plant and siphons it onto a nearby boat, continued as well.
The Lake Dunmore Fern Lake Association also has actively pursued control on 40 acres of Lake Dunmore with an invasive-milfoil-specific herbicide in June 2016.
“The effect was dramatic,” said James C. Foley Jr., president of the association. “It did not affect native milfoils or other plants and did no harm to fish.”
Other control efforts such as suction harvesting had not been sufficient — one of the key criteria for an herbicide permit, he said.