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 came 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 [that] as a feasible alternative to using the herbicides, particularly this year,” he explained. “[That] 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.”
After a deep drawdown this winter, the plan to use herbicides was accepted without an assessment of the effectiveness of the drawdown. Drawdown has been effective in the past.Given the cold temperatures this past winter, it is unconscionable to spread poisons on a problem which may already be improved this year. The poisons are not a solutions.
Well said, and fully supported by science.
Sadly this result goes against all current scientific knowledge.
A direct, evidence-based assessment of the Conservation Commission’s decision suggests that, while well-intentioned, the approval of repeated herbicide applications reflects a short-term management approach that is not strongly supported by current lake science and may, in fact, exacerbate underlying ecological and public health risks.
First, the Commission’s own record indicates that herbicide use has not produced durable outcomes. Treatments applied in 2024 were followed by a rapid resurgence of invasive species the following year. This pattern is consistent with established limnological research showing that chemical control of aquatic macrophytes often provides only temporary suppression, particularly in nutrient-rich systems where regrowth is driven by sediment nutrient recycling and propagule persistence (Carpenter & Lodge, 1986; Smith et al., 1999). The documented “return with a vengeance” is therefore not an anomaly, but a predictable response in systems where root structures and seed banks remain intact.
Second, the decision appears to insufficiently account for well-documented ecological feedbacks associated with herbicide use. The decomposition of chemically killed vegetation can release stored nutrients—particularly phosphorus—back into the water column, increasing the risk of eutrophication and harmful algal blooms (HABs) (Søndergaard et al., 2003; Paerl & Otten, 2013). This dynamic directly contradicts long-term water quality objectives and may worsen the very conditions that favor invasive species dominance. In this context, continued reliance on herbicides risks reinforcing a cycle of treatment and regrowth rather than resolving root causes.
Third, the claim that selective dosing can prevent collateral ecological damage warrants more scrutiny than was reflected in the discussion. While modern aquatic herbicides such as flumioxazin and endothall-based formulations can be applied in targeted ways, peer-reviewed evidence indicates that non-target impacts—including effects on native vegetation, invertebrates, and fish habitat—remain a concern, particularly under repeated or large-scale applications (Netherland, 2015; Madsen et al., 2008). The scale of the proposed treatment area (approximately 50 acres) further increases the likelihood of system-wide ecological effects.
Fourth, potential human health considerations, while often characterized as low-risk under regulatory guidelines, are not negligible. Aquatic herbicides approved by the U.S. Environmental Protection Agency are deemed safe when used according to label instructions; however, this standard reflects acceptable risk thresholds rather than absence of risk. Concerns regarding exposure pathways—particularly for recreational users and private well systems hydraulically connected to surface waters—remain an active area of study (Battaglin et al., 2014). A precautionary approach is typically recommended in public water bodies with mixed uses.
Finally, and most importantly, the decision appears to constrain future management flexibility rather than expand it. Repeated chemical interventions can delay or disincentivize investment in more sustainable, system-based strategies such as watershed nutrient reduction, sediment management, biological controls, and integrated mechanical approaches. Contemporary best practice in lake management increasingly emphasizes integrated pest management (IPM) frameworks, where chemical treatment is a limited and carefully bounded tool—not a recurring primary strategy (Hussner et al., 2017).
In sum, the Commission’s unanimous approval does not align well with the weight of current scientific evidence. The approach prioritizes short-term visual control over long-term ecological stability, introduces avoidable environmental and health uncertainties, and risks locking the lake into a cycle of dependency on repeated chemical treatment. A more scientifically grounded strategy would focus on nutrient source control, adaptive integrated management, and reduction of system-wide drivers of invasive growth—thereby preserving both ecological integrity and future management options.
References (Harvard style)
Battaglin, W.A. et al. (2014) ‘Glyphosate, other herbicides, and transformation products in midwestern streams’, Journal of the American Water Resources Association, 50(2), pp. 275–290.
Carpenter, S.R. and Lodge, D.M. (1986) ‘Effects of submersed macrophytes on ecosystem processes’, Aquatic Botany, 26, pp. 341–370.
Hussner, A. et al. (2017) ‘Management and control methods of invasive alien freshwater aquatic plants’, Aquatic Botany, 136, pp. 112–137.
Madsen, J.D. et al. (2008) ‘Aquatic plant management: ecological effects of herbicides’, U.S. Army Corps of Engineers Report.
Netherland, M.D. (2015) ‘Chemical control of aquatic weeds’, Pest Management Science, 71(3), pp. 362–370.
Paerl, H.W. and Otten, T.G. (2013) ‘Harmful cyanobacterial blooms: causes, consequences, and controls’, Microbial Ecology, 65, pp. 995–1010.
Smith, V.H. et al. (1999) ‘Eutrophication: impacts of excess nutrient inputs on freshwater, marine, and terrestrial ecosystems’, Environmental Pollution, 100, pp. 179–196.
Søndergaard, M. et al. (2003) ‘Role of sediment and internal loading of phosphorus in shallow lakes’, Hydrobiologia, 506–509, pp. 135–145.