Lake Iroquois milfoil treatment unlikely this year

An herbicide treatment of Lake Iroquois in Chittenden County isn’t likely to occur this year because the state received so many public comments that it will not have time to respond before the window has passed in which the first treatment must occur.

The chemical fluridone would have to be administered by the end of May if it is to be used on the lake this year, said Misha Cetner, a permit analyst for the state Department of Environmental Conservation’s Watershed Management Division.

This would be the first time for such a treatment in Lake Iroquois, but the same chemical has been used numerous times in other Vermont waterbodies in the past, state officials say.

The likelihood is “very slim” that the application to dose the lake with fluridone will be approved in time to put it into the water this year, Cetner said. He said he must write a response to each of public comment before the permit can be approved, and that “it’ll take some time.”

The first treatment must be made between mid-May and the end of May, officials said.

Many of the nearly 50 comments submitted recently came during a May 4 public workshop on the issue held in Hinesburg.

The aquatic herbicide would be used to kill off the invasive species Eurasian watermilfoil.

The Lake Iroquois Association is hoping for a five-year permit, said President Pat Suozzi. If permission comes too late for this year, the group will wait until next year, she said.

The lake is bounded by Williston, Hinesburg, Richmond and St. George.

Williston submitted the application in its name on behalf of the lake association, said Town Manager Richard McGuire.

The town didn’t initiate the process, McGuire said; the selectboard did approve $20,000 for the effort, he said.

Eurasian watermilfoil has taken over nearly a third of the lake’s surface area and two-thirds of the shoreline.

There appears to be no alternative to the herbicide use, Suozzi said, and the lake’s milfoil infestation appears to be killing off native aquatic plants.

The lake association will apply extremely low concentrations of the herbicide to the lake’s water, roughly five to eight parts per billion, Suozzi said, which is a level that poses no health threats to humans. Nearby lake dwellers who draw their drinking water from the lake will get bottled water as long as the herbicide is present, however, she said.

The association could dose the lake with fluridone as many as three times, she said — first in mid-May to late May, another more targeted application 30 days later, and potentially a third treatment still later in the season if conditions warrant.

Although representatives from the state say the herbicide won’t unduly harm species other than milfoil, critics of the practice say it does harm fish, even if it works as intended.

Some of the best fishing in a lake or pond occurs at the border between milfoil and open water, said Shawn Good, a fisheries scientist with the Vermont Fish and Wildlife Department. That’s because big fish prey on juvenile fish that live within the milfoil, he said, and juvenile fish live in milfoil because it offers nutrients and protection and the other qualities that define a good fish habitat, he said.

Fish can’t distinguish between native species and invasive milfoil, Good said, and they flourish in milfoil just as readily as in any other dense aquatic foliage.

When lake associations like the Lake Iroquois Association apply lake-wide herbicide, it kills off all the milfoil, leaving the fish without their accustomed habitat.

Most of Lake Iroquois doesn’t need to be treated for milfoil, since the majority of the lake’s surface is open and uninfested, Good said, and most lakes in Vermont don’t need the sort of lake-wide herbicide applications that lake associations in the state seem to prefer.

That’s because milfoil doesn’t typically grow in waters deeper than 20 feet, Good said. Most lakes and ponds in the state that suffer from milfoil infestations have the plant developed in shallow areas near shoreline, but open water remains further out, where the water body’s floor is too deep for milfoil to get established.

A lake with a milfoil infestation and more than half its area free of the invasive plant still serves as a functional ecosystem, Good said. Such a lake provides much better habitat for fish than the same lake following an herbicide treatment, when the milfoil that once provided living quarters for small fish lies rotting on the bottom of the lake.

As a result, Fish and Wildlife biologists have long called for an end to the practice of lake-wide herbicide applications, Good said, but they’re powerless to stop the practice because it’s the Department of Environmental Conservation that actually issues the permits.

The DEC issues permits for such treatments so long as they meet five criteria, Cetner said.

Namely, if there’s no suitable alternative, if there’s an acceptable level of risk to the environment, if there’s a long-term management plan, if there’s public benefit and if there’s no public health hazard in doing so, the DEC issues permits for aquatic herbicide, Cetner said.

The DEC has been approving fluridone treatments since 2000, and department scientists have had ample time to study the effects of these treatments on plants and animals in the places where it’s been applied, Cetner said.

Evidence from previous applications shows that fluridone applications meet all five approval criteria, Cetner said.

“Nothing has shown up indicating we can’t make the findings,” he said.

Although Fish and Wildlife biologists have complained in the past about these applications, Cetner said, they’ve provided nothing to the DEC yet to support a sudden change in the department’s historic stance toward the chemical, Cetner said.

In an email to Good, Cetner said that his department is bound by precedent to continue making these approvals unless compelling scientific evidence shows that a change is needed.

“There are some areas of disagreement regarding these types of aquatic invasive species control projects between DEC and F&W,” Cetner wrote. “Based on the current management strategies and the permit history allowing those strategies to be enacted, any shift from that would need scientific data supporting the need for change, which would then need to be significant enough of an issue to overturn permit history and the statutory findings used to approve projects.

“Any shift would also need to be communicated to the public to show how we at the State might view projects differently and set a different level of expectations for the public as to what might be approved,” Cetner wrote. “As a regulator, I can’t suddenly say no to an applicant for a project that has been routinely approved elsewhere in the state without proper scientific and statutory support to do so.”

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  • Milo MacTavish

    Human intervention to correct human intervention almost always makes it worse. Have you learned nothing from the cane toad? Twenty years is not ample time to study the long term effects of these applications.

  • Jason Brisson

    “There appears to be no alternative to the herbicide use”
    Weevils, manual pulling, mechanical harvesting, and application of sunken landscape fabric panels to swimming areas.
    “Eurasian watermilfoil has taken over nearly a third of the lake’s surface area and two-thirds of the shoreline.”
    Eurasian milfoil needs to be attacked when its found, and not allowed to flourish. The problem would not be so bad now/herbicide would not be needed had it been addressed earlier!

  • Brian Otley

    This species is rendering Lake Iroquois unusable and its growth is exponential. Other mitigation techniques have been assessed and are not long term viable due to the extent of the invasion for cost or effectiveness reasons. Other lakes in Vermont have reversed the impacts of milfoil successfully and recaptured the original uses of the lake. The fact that all public comments have to be responded to before the permit can be approved demonstrates the ineffectiveness of state process. Let’s reclaim this body of water for the range of recreation it has historically supported and not limit it to only those that are viable with a milfoil infestation. The milfoil issue at Lake Iroquois has been studied for more than 5 years now. The current plan by the Lake Association is the right plan. Time is not going to help arrive at a better decision. Let’s go.