The Conservation Commission at a nearly four-hour meeting on Tuesday voted 5-0 to approve the limited use of herbicides in Lake Maspenock, as it had done two years before.

Kerry Reed, the Department of Public Works director, explained that the DPW has a “toolbox of weed management options” that the Conservation Commission approved in 2022. The toolbox, she said, was based on 10 years of data collection. It includes extended drawdowns of the lake, hand harvesting and herbicide treatments as a last resort.

Herbicides applied in the summer of 2024 were effective in killing the invasive species overgrowth in the north basin, Reed added. But the following year, the weeds cam back with a vengeance.

New companies hired to survey, attack weeds

The town hired a new limnologist company called Aquatics Restoration Consulting (ARC) in 2025 to complete its annual vegetation survey.

Certified lake manager Wendy Gendron said she was familiar with the issues at Lake Maspenock. While the ARC survey she did showed “quite a bit of diverse vegetation,” it also had five nonnative species.

ARC documented brittle naiad, tapegrass, Eurasian milfoil, variable milfoil, fanwort, bladderwort and pondweed during two surveys last summer. Gendron said the “most dangerous” one for the lake is fanwort because it chokes off native plants and impacts fisheries.

“Fanwort has the capability to really take over the entire lake,” she stressed.

The others also can “get very aggressive” and deprive organisms of oxygen.

Added Gendron: “Those other ones can really destroy the ecology of the lake if left to completely spread.”

The major concern Gendron had is that these plants have begun to migrate into the south basin.

Recos asked about the reasons for the new pattern in weed growth. Gendron said that lakes have natural variability. In addition, there is “competition” between some species.

SOLitude, a company hired earlier this year, will be performing the herbicide application. It will focus on about 50 acres in the north basin as well as the cove by the boat ramp and the area south of Sandy Beach. Triune, ProcellaCOR and flumioxazin will be used.

LMPA, CIG engage in outreach, research

On a positive note, the water quality achieved through samples was considered good, Reed said. The DPW has been working with the Health Department, the Citizens Input Group (CIG) and the Lake Maspenock Preservation Association (LMPA) to collect and analyze water samples.

LMPA president Sabine St. Pierre explained that the group has focused on resident outreach and public education. It has worked with landscaping companies, urging them to use non-phosphorous fertilizers in accordance with state law.

Additionally, she has been researching the boat ramp monitoring program sponsored by the state’s Department of Conservation and Recreation.

“We also feel that if we can start to control what’s coming into the lake, that will be helpful in mitigating future growth,” St. Pierre said.

Mechanical harvesting may be future option

CIG chair Joe Baldiga said the group has been doing extensive research on mechanical harvesting and has reached out to other communities that use this option.

“At this point, we don’t see them as a feasible alternative to using the herbicides, particularly this year,” he explained. “[They] may be part of a pilot program for next summer if the weeds come back.”

Reed said that her research showed that even with mechanical harvesting, the weeds come back. She said it could be used as one of the management tools, but that the area would have to be “continuously managed.”

Added Baldiga: “Harvesting does not discriminate.”

Critics push back

Donald Sutherland, Carol Esler and Donald Keiser continued to voice strong opposition to chemical use.

Sutherland, a member of the Sustainable Green Committee and the Water & Sewer Advisory Board, said Environmental Protection Agency research showed that herbicide use only mitigates the issue in the short term. He added that nutrients from the dead plants spread, leading to future growth. This could create toxic algae blooms.

Esler, also an SGC member, has lived on the lake for 40 years with her husband, Keiser.

“I am completely opposed to the ecological, irresponsible and dangerous request to use poisons in our lake,” she said.

She suggested looking into an echo harvester or suction harvesting.

Keiser asked how an herbicide can be targeted to a particular species “and not have collateral damage.”

Gendron responded that is “a matter of dosing” after using scientific studies.

Recos said the commission approved the toolbox for a five-year use period so that its effectiveness could be monitored. The decision voted on at this meeting was whether herbicide use was an “appropriate measure for this year given the data that’s been collected.”