HopNews
The Citizens Input Group (CIG) met on February 11 to review how Hopkinton should manage aggressive weed growth in Lake Maspenock. They focused on the North Basin, as that is where invasive weeds primarily grow. The discussion centered on three things:
- Effectiveness of this winter’s deep drawdown
- Return of invasive weeds after the 2024 herbicide treatment
- Whether non-chemical options can realistically replace herbicides
The Lake Maspenock Weed Management & Control Advisory Group, commonly referred to as the CIG, or the “weed committee,” is a resident-led committee that advises the town (DPW, Select Board & Conservation Committee) on controlling aquatic weeds.
Drawdown Helped, But Conditions Not Ideal
Committee members opened the meeting by assessing the extended winter drawdown. The purpose is to expose and freeze weeds along the shoreline. Several members noted that early ice formed on the lake before the water reached the desired low level. This created a layer of ice with water still flowing underneath. That raised safety concerns and forced the town to stop the drawdown. It was about half a foot to a foot higher than planned.
Members said the cold temperatures and the duration of freezing this winter were better than in recent years, but the ice and snow cover may have limited weed kill. One member described ice as “the enemy,” because water under the ice remained too warm to effectively kill plants. The group agreed the drawdown was probably more effective than in the past few years, but that its impact will not be clear until late spring and summer.
Consultant Report Shows Invasive Weeds Have Returned
The committee reviewed a December 2025 report from the lake consultant, Aquatic Restoration Consulting (ARC). ARC documented five key non-native invasive species in Lake Maspenock: fanwort, variable water milfoil, Eurasian water milfoil, curly-leaf pondweed, and brittle naiad.
A post-treatment survey conducted by the vendor Solitude in 2024 found that invasive weeds were essentially absent in the treatment area, with only sparse fanwort present. By August 2025, however, ARC’s survey of roughly 70 stations found that non-native invasive weeds had returned in strong numbers in the North Basin and again required control.
ARC also concluded that a single annual survey is sufficient and in line with typical practice across the state. The consultant further reported that neither the extended drawdown nor the 2024 herbicide application appeared to cause a negative impact on the overall lake ecosystem.
Sustainable Green Committee Presses for Non-Chemical Solution
Representatives from the Sustainable Green Committee (SGC) addressed the meeting. Both committees share the same first choice: non-chemical solutions. SGC members cited federal and state research indicating that herbicides offer short-term control and can lead to a “herbicide treadmill,” where repeated applications are needed year after year.
HopNews did some research on the aquatic “herbicide treadmill” and how to prevent it. It turns out that we are already doing many of the right things.
- Don’t use herbicides every year. We don’t. We’ve done it once.
- Mix things up, adjust water levels if possible—we do that every year.
- Use herbicides sparingly and focus on trouble spots. In 2024, we treated only the north basin with one gallon of herbicide per acre.
- Rotate the herbicides used to prevent resistance from building. We discussed that, and we plan to investigate changing the herbicide next time.
- Add shoreline buffers and reduce nutrient inputs directly into the water when possible. That is now part of ConComm’s requirements.
- Track plant growth and water quality every season. We’ve done that for many years.
- Use what you learn to fine-tune your approach, so over time, you need fewer treatments—and the ones you do use hit the mark. That’s why the CIG was formed.
Lake Association Focuses on Prevention and Water Quality
Leaders from the Lake Maspenock Preservation Association (LMPA) described work underway to reduce nutrient and weed inputs into the lake. Water testing in Lake Maspenock (since 2015) has consistently shown that high phosphorus levels are not a problem. In fact, they never have been a problem.
But to be on the safe side, LMPA has included public campaigns against phosphorus-heavy lawn fertilizers throughout the lake and watershed. This is in coordination with the Conservation Commission. They are also looking to enforce and possibly expand existing fertilizer buffer zones near the water. They’re reaching out to landscapers and lakefront homeowners to ensure everyone understands the rules on runoff and fertilizer use. The focus is clear: keep the lake clean, start with what goes into it.
LMPA and Sustainable Green Committee (SGC) Working Together
The two groups are exploring strategies to reduce weed introductions from boats arriving from other lakes. Most lakes in New Hampshire require boats to be washed before launching. This would be difficult to implement here as the runoff would go directly back into the lake.
Residents Describe Summer Weed Impacts
Several North Basin residents spoke about how weeds affected recreation last summer. A homeowner on Downey Street said that early in the summer, there were almost no weeds. He could easily swim with his young daughter. But by late summer, they “really couldn’t swim at all” due to dense growth.
One neighbor said his kids could only swim comfortably near their house the year the herbicide treatment happened.
People living along Lakeshore Drive and tucked away in the coves agreed—they saw a real drop in weeds and a better place to swim and boat after the 2024 treatment.
A fisherman who’s spent nearly thirty summers on the lake put it simply: the treatment made things much better, and fishing or wildlife didn’t suffer.
Another homeowner pointed out that, even though the 2024 treatment focused mostly on the North Basin, weeds also pulled back in the middle basin near his place.
Mechanical Harvester Proposal Sparks Debate
Lake resident Don Kaiser proposed using a mechanical weed harvester instead of herbicides. He said traditional harvesters cut weeds like a lawnmower, which is ineffective. But newer designs, such as an “Eco Harvester,” pull plants out by the roots.
Kaiser argued that, by investing once in equipment the town could reduce reliance on herbicides. He suggested temporarily placing harvested weeds on a rocky island area in the lake to dry and reduce hauling costs. CIG members responded that harvesting has always been part of their “toolbox” discussions, but that it comes with significant challenges.
- Need for staging the large volumes of plant biomass to dry
- Cost and logistics of removal
- The likelihood that weeds would regrow more quickly than with herbicides (for harvesters that cut the weeds)
- Concern about the North Basin’s extensive rock fields that would make harvester operation difficult and potentially damaging.
Committee Chair Joe Balidga added that, unlike boaters seeking a simple navigation channel, the committee’s concern is the long-term health of the lake and preventing the North Basin from turning into a “grown-in swamp.”
LMPA and other residents raised additional questions about whether placing weed piles on small rock islands would truly remove the material from the system, given that runoff and birds would spread fragments back into the water.
Eco Harvester
HopNews was intrigued, so we did a little research. The Eco Harvester is made by Silver Mist Aquatics in Wisconsin. They are sold through distributors such as Weeders Digest. A setup for the north basin (60ish acres) would cost ~$150-100K for the harvester and a trailer. Then there is the need for a dumping spot for the biomass to dry, away from homes, due to the “stink” factor. The equipment would need a place to be stored when not in use.
Herbicides Just One Tool in the Toolbox
Throughout the meeting, CIG members emphasized that herbicides are just one tool in a broader management plan. They noted that the committee intentionally did not pursue a lake-wide broadcast treatment. This is despite pressure from some residents to treat the entire lake. Instead, they focused on targeted applications in the North Basin combined with drawdowns, monitoring, and prevention measures.
The town skipped herbicide treatment in 2025 after determining the 2024 application was highly effective. This confirms that the committee does not support automatic annual treatments.
The CIG disagreed with characterizing herbicide use as “irresponsible” or ineffective. They argued that the 2024 treatment successfully reduced invasive weeds and reduced plant biomass. (The biomass dies back into the sediment and fuels future growth.)
Public Outreach and Boat Education
The conversation turned to ways to limit new weed introductions, especially from visiting boats. LMPA members are coordinating with the Conservation Commission on signage and education at the town boat ramp. LMPA President Sabine St. Pierre recently completed the state boating safety course noted that while the class mentions nuisance weeds, it does not clearly explain that boaters are legally required to clean their boats before launching.
St Pierre plans to ask the Department of Environmental Protection to include stronger messaging about this legal requirement in course materials and handouts. “This is a missed opportunity, given that hundreds of boaters will undergo certification between now and 2028,” said St.Pierre.
Funding and Permitting Path for 2026 Treatment
Department of Public Works (DPW) Director Kerry Reed outlined the process and timeline for a potential 2026 herbicide treatment. Funding for the treatment is already proposed in the town’s Fiscal Year 2027 budget, which runs through June 30, 2027, and includes the summer of 2026. That budget will go before the Select Board in early March and then to Town Meeting on May 2.
On the permitting side, Hopkinton already holds an Order of Conditions from the Conservation Commission that authorizes the full suite of management tools, including herbicides. Each year, CIG must present its proposed treatment plan to the commission, but this is now handled as a work session rather than a new public hearing.
Reed said she will first move through the town’s procurement process to select a vendor, likely through competitive bidding that could include Solitude or other firms.
Once a vendor is on board, the town and ARC will refine technical details such as which herbicide to use, dosage rates, and treatment areas, then present that information to the Conservation Commission in late March or early April. ARC’s recent report referenced potential alternative products, but Reed said the previous product remains the most common and cost-effective, and that final choices will be based on the pre-treatment weed survey.
The vendor will conduct a pre-treatment survey in late spring to confirm which species are present and where, and must also complete a post-treatment survey, as required under the existing permit. The timing of any treatment will seek a “sweet spot” when plants have grown enough biomass to absorb the herbicide but before they reach peak density, which last time was around mid-June.
No New Public Hearing, But Dialogue Will Continue
Reed clarified that because the Conservation Commission and Select Board have already granted the core approvals, there will be no new formal public hearings or abutter notifications specifically on herbicide use.
Future Conservation Commission discussions will not be required to include public comment, and the Select Board will not take another up-or-down vote on treatment each year.
Residents can still speak at Select Board public forums, and LMPA is committed to keeping lake residents informed.
CIG members stressed that they view meetings like this as important opportunities for residents and town committees to be heard.
CIG and SGC leaders both want to collaborate
- Fertilizer rules
- Boat-cleaning rules
- Exploration of feasible non-chemical options
Both groups share the same goal
- Preserving the health of Lake Maspenock
- Protecting its ecosystem
- Keeping it usable for swimming, boating, and fishing
- Protecting wildlife for years to come
It’s important the everyone is aware of the facts regarding the use of chemicals for lake weed control.
For example, the aquatic herbicide diquat dibromide (commonly referred to as diquat) is a fast-acting, non-selective contact herbicide widely used for submerged aquatic vegetation control.
However, scientific evidence demonstrates:
Environmental Risk
Diquat is highly toxic to aquatic invertebrates and can pose risks to non-target organisms, particularly under repeated or high-dose applications. It binds to sediments and can persist in benthic environments, where it may affect sediment-dwelling organisms (U.S. EPA, 2020; Solomon et al., 2013). Rapid plant die-off can also lead to oxygen depletion, contributing to fish stress or mortality in some systems (Netherland, 2014).
Limited Long-Term Effectiveness
Diquat is a contact herbicide that destroys exposed plant tissue but does not typically kill root systems of perennial species. As a result, regrowth is common, often requiring repeated applications to maintain suppression (Netherland, 2014; Getsinger et al., 1997). This supports the statement that control is often ineffective without continued treatment.
Short Water-Column Persistence, but Ecological Impact
While diquat dissipates relatively quickly from the water column due to adsorption to sediments, this does not eliminate ecological concern, as sediment accumulation can prolong exposure pathways for benthic organisms (U.S. EPA, 2020).
Taken together, the literature supports the position that aquatic herbicides such as diquat can have environmentally detrimental effects and typically require repeated application for sustained vegetation control.
References (Harvard style)
Getsinger, K.D., Netherland, M.D., Grue, C.E. & Koschnick, T.J. (1997) Improvements in the use of aquatic herbicides and establishment of future research directions. Journal of Aquatic Plant Management, 35, pp. 71–76.
Netherland, M.D. (2014) Chemical control of aquatic weeds. In: Gettys, L.A., Haller, W.T. & Petty, D.G. (eds.) Biology and Control of Aquatic Plants: A Best Management Practices Handbook. 3rd edn. Marietta, GA: Aquatic Ecosystem Restoration Foundation, pp. 71–88.
Solomon, K.R., Dalhoff, K., Volz, D. & Van Der Kraak, G. (2013) Effects of herbicides on aquatic organisms. In: Tierney, K.B., Farrell, A.P. & Brauner, C.J. (eds.) Fish Physiology, Vol. 33. San Diego: Academic Press, pp. 357–404.
U.S. Environmental Protection Agency (EPA) (2020) Registration Review: Diquat Dibromide – Interim Decision Case Number 0288. Washington, DC: U.S. EPA.
As a prior long term member of the Hopkinton Conservation Commission and participant in lake studies, my recommendation to seek alternatives to chemical weed control. The most effective are weed management programs that
Response to CIG Article on Lake Maspenock Weed Management
Several statements in the February 13 article present an incomplete or misleading picture of aquatic herbicide use and lake ecology.
1. “No negative ecosystem impact” is not the same as “no impact.”
The consultant’s conclusion that the 2024 herbicide treatment did not cause a “negative impact” appears based on limited post-treatment indicators. However, contact herbicides such as diquat dibromide are non-selective and toxic to aquatic invertebrates and plankton at certain concentrations (U.S. EPA, 2020). Rapid vegetation die-off can also contribute to short-term oxygen depletion and nutrient recycling within sediments (Netherland, 2014). Absence of observed fish kills does not equate to absence of ecological impact.
2. A single annual survey is not robust monitoring.
Best-practice lake management generally recommends adaptive management informed by multi-season monitoring, particularly before and after chemical intervention (Getsinger et al., 1997). One annual survey provides limited data on plant regrowth cycles, dissolved oxygen dynamics, or long-term shifts in species composition.
3. The “herbicide treadmill” concern is well-documented.
Contact herbicides typically kill above-ground biomass but do not reliably eliminate root systems or seed banks of perennial invasives. Regrowth within one growing season is common, often leading to repeated treatment cycles (Netherland, 2014). The reported return of invasive species within one year is consistent with this pattern.
4. Biomass dieback does recycle nutrients.
While treatment reduces visible vegetation, decomposing plant biomass returns nutrients—particularly phosphorus—into sediments, potentially fueling future growth (Carpenter & Lodge, 1986). The article acknowledges biomass dies back into sediment but does not address the long-term internal loading implications.
5. Prevention is more cost-effective than repeated suppression.
Nutrient management, shoreline buffers, watershed controls, and boat-cleaning enforcement are widely recognized as foundational components of sustainable lake management (Carpenter et al., 1998). Chemical control is typically considered a short-term suppression tool, not a standalone solution.
Conclusion
The article frames herbicide use as limited, controlled, and largely impact-free. The scientific literature supports a more nuanced position:
Contact herbicides provide short-term suppression.
Regrowth and repeated treatment are common.
Ecological impacts may occur even when not immediately visible.
Long-term lake health depends primarily on watershed nutrient control and prevention strategies.
A balanced public discussion should reflect these realities rather than suggesting that absence of visible harm equals ecological neutrality.
References (Harvard style)
Carpenter, S.R. & Lodge, D.M. (1986) Effects of submersed macrophytes on ecosystem processes. Aquatic Botany, 26, pp. 341–370.
Carpenter, S.R., Caraco, N.F., Correll, D.L., Howarth, R.W., Sharpley, A.N. & Smith, V.H. (1998) Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecological Applications, 8(3), pp. 559–568.
Getsinger, K.D., Netherland, M.D., Grue, C.E. & Koschnick, T.J. (1997) Improvements in the use of aquatic herbicides and establishment of future research directions. Journal of Aquatic Plant Management, 35, pp. 71–76.
Netherland, M.D. (2014) Chemical control of aquatic weeds. In: Gettys, L.A., Haller, W.T. & Petty, D.G. (eds.) Biology and Control of Aquatic Plants: A Best Management Practices Handbook. 3rd edn. Marietta, GA: Aquatic Ecosystem Restoration Foundation, pp. 71–88.
U.S. Environmental Protection Agency (EPA) (2020) Registration Review: Diquat Dibromide – Interim Decision Case Number 0288. Washington, DC: U.S. EPA.
The herbicide used by Solitude was Tribune (diquat dibromide). It is recommended to be used at 1-2 gallons per acre. Solitude applied it at the smallest dose of one gallon per acre. It was used to spot treat the north basin only where the weeds were the worst.
“Single annual survey is not robust monitoring” Lake weeds have been surveyed several times per year for the last 10 years—check the reports on the LMPA website.
Herbicide Treadmill occurs through a repeating cycle of resistance and increased chemical use. We’ve used herbicides once, two years ago.
We don’t yet know if we will need herbicide this year nor do we know what ARC will recommend if we do need to treat.
“Nutrient management, shoreline buffers, watershed controls, and boat-cleaning enforcement are widely recognized as foundational components of sustainable lake management” All of those choices have been researched and discussed. The information is on the LMPA website. And the minutes from all the meetings are available on the town website.
Please note that Phosphorus is not a problem in the lake as seen by all the Microbac water testing results (done several times per year), also shown on the LMPA website.
A direct, evidence-based assessment of the Conservation Commission’s decision to support herbicide treatments 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.