State OKs herbicide use for Lake Iroquois

Chemical treatment set for June 28


Special to the Observer

The Vermont Department of Environmental Conservation (DEC) has approved a permit to use the chemical herbicide ProcellaCOR to treat invasive milfoil in Lake Iroquois.

The Lake Iroquois Association (LIA) and the Lake Iroquois Recreation District (LIRD) jointly filed an Aquatic Nuisance Control Permit Application with the department last spring. It took nearly a year, but in February they received the affirmative response they were waiting for.

The approval follows a 2018 denial by the department for the LIA to use the herbicide Sonar in Lake Iroquois.

Pat Suozzi, former LIA president and current secretary, was relieved when the permit was approved.

“This means a lot to the LIA and LIRD,” said Suozzi. “It’s been seven years in the making, and hopefully, this approval will allow us to really deal with the problem.”

The treatment will be administered on June 28 by SOLitude Lake Management, a Massachusetts company that has treated a number of Vermont lakes. Someone from the Vermont Department of Agriculture will meet company personnel in the early morning to oversee the process. The Vermont Department of Agriculture pesticide inspector will be notified and will inspect the boat and the herbicide application mechanisms before treatment is underway.

The littoral zone in the northern part of the lake has been designated for treatment this year as the milfoil is dense in that location.

Littoral zones are near the shore and shallow areas, and are the only places where the chemical will be used.

ProcellaCOR is not sprayed, but injected, which allows for precise treatment. The dosage is minuscule. The rate of application will result in no more than .47 parts per billion (PPB) lakewide. With a half-life of .07 days (1.68 hours), ProcellaCOR is not expected to be detectable in the water within 24 hours of treatment. The LIA and LIRD are only permitted to treat 40 percent of the littoral zone.

It is recommended that the lake not be used on the day of treatment. There are minor restrictions on irrigating lawns with lake water for the first few days following the treatment. The Lake Iroquois Association will inform residents of any necessary details about the treatment by mail in advance.

Misha Cetner oversees the DEC’s Lakes and Ponds Program and was the permit analyst for the Aquatic Nuisance Control permit.

In an email, he wrote that ProcellaCOR “is highly targeted to controlling Eurasian watermilfoil while beneficial native aquatic plant species are largely unimpacted.”

Cetner went on: “A key difference between this permit and the previous denial for an herbicide treatment in Lake Iroquois is that ProcellaCOR can be used to target specific areas of dense Eurasian watermilfoil to control where the herbicide typically breaks down within days, whereas Sonar was semi-targeted to controlling Eurasian watermilfoil at low concentrations where that type of treatment required a concentration of the herbicide to be maintained throughout the entire waterbody for up to several months during the late spring/early summer.”

The DEC no longer issues permits for the use of Sonar.

Not everyone agrees that the use of herbicides is the best solution to the milfoil problem. Meg Handler is a Hinesburg resident and was a member of the LIA when it voted on whether to request permission from the state to use Sonar.

She opposes herbicide use in the lake, a position that put her in the minority in the association.

“It went against everything I was told,” said Handler. “All our efforts to keep the lake chemical-free, and now we were looking at it as a solution?”

Handler helped organize a local group of individuals who opposed the use of Sonar.

“It was really a citizens, grassroots effort,” she said. “We all had to educate ourselves on the topic and, in the end, it was our skepticism and research that led the DEC to change their policies statewide.”

Handler believes the LIA applied for the Sonar permit without sufficient research or evidence of the chemical’s safety.

“It’s important to note that, had the LIA gotten permission to apply Sonar to Lake Iroquois, they would have used it,” said Handler.

She argues that aquatic herbicides will not control the milfoil, but instead disrupt the natural ecology of the lake.

“The LIA will claim success in the short term, but the milfoil will come back and the ecology of the lake will be worse than before,” she said.

Jeff Davis, chair of the LIRD board, expressed confidence in this approved treatment to reduce milfoil, based on the success seen in other Vermont lakes.

“Three to four lakes were treated with ProcellaCOR last year and quite a few were approved for this summer,” said Davis.

After the 2018 permit denial, the LIA sought out other mitigation strategies for removing milfoil from the lake. To remedy the swim-area watermilfoil infestation, divers were enlisted to remove it by hand from its roots at the bottom of the lake. Barrier mats were also placed on top of the weeds, which kill the vegetation by blocking its access to sunlight. Because both of these efforts require volunteers, the association did not deploy these mitigation strategies in 2020 due to the challenges posed by COVID-19.

According to Suozzi and Davis, the milfoil infestation is too dense to control all by hand, which makes this approval crucial to the mitigation process. The LIA plans to run its diver program this summer too, and use that strategy to control any regrowth, although Davis admits uncertainty that divers will be enough.

“It’s like a game of whac-amole,” Davis said.

He does not rule out the possible need for additional chemical treatments in the future.

Handler, however, questioned milfoil’s status as a nuisance weed.

“It’s inconvenient for humans who want to recreate in the lake,” she said.

She suggested that, before applying for a permit, associations like the LIA should be required to address shoreline erosion, runoff from roads, excessive boat use, inappropriate boat use and the transportation of invasive species from lake to lake.

The LIA and LIRD are currently running programs that address these concerns. Davis is involved in Beebe Lane road improvements with the goal of improving runoff and reducing a big source of sediment into the lake.

Maddy Holden is reporter with the Community News Service, a collaboration with the University of Vermont’s Reporting & Documentary Storytelling program.