Milfoil on Swains Lake.
Updated 02/01/2026
Everything You Need to Know About This Year’s Treatment Strategy
Securing the funding for our 2026 treatment was a massive hurdle, but the work is just beginning. As an Association, we believe it is vital that every resident understands the "what, why, and how" of the NH DES-approved plan to protect Swains Lake from Variable Milfoil.
The Target: Variable Milfoil
Variable Milfoil (Myriophyllum heterophyllum) is not just an "annoying weed." It is an aggressive, invasive species that can grow up to an inch a day, forming dense mats that choke out native plants, ruin fish habitats, and make swimming and boating nearly impossible.
The 2026 plan is designed to be a "one-two punch" to stop the spread that began near the public boat launch and has migrated to various areas of the lake.
The Strategy: A Two-Pronged Attack
Our $44,110 management plan, developed in coordination with the NH DES, utilizes two primary professional methods:
1. ProcellaCOR Herbicide Treatment ($26,510)
Unlike older herbicides that simply "burned" the leaves off the plant, ProcellaCOR is a game-changer. It is a systemic herbicide, meaning it is absorbed by the plant and travels down to the root system to ensure the plant cannot grow back.
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Precision: It is highly selective and targets milfoil specifically while leaving native "good" plants alone.
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Safety: It has a very low application rate and is used in extremely small concentrations.
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Logistics: This treatment usually takes place in late June or early July when the milfoil is actively growing.
2. DASH (Diver Assisted Suction Harvesting) ($17,600)
For smaller, scattered patches where herbicide isn't the most efficient tool, we employ professional dive teams.
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How it works: Divers go sub-surface and hand-pull the milfoil by the root, fed into a suction hose that brings the plants to a boat for disposal.
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Prevention: This method is critical because it prevents "fragmentation." A single broken piece of milfoil the size of a fingernail can float away, take root, and start a whole new colony.
The Financial Breakdown
We want to be fully transparent about where the $44,110 is going and how it is being paid for:
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NH DES Grant (Secured): $22,055 (50% Match)
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BCC Contribution (Committed): $20,000 (Specifically for professional bills)
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SLA Responsibility: $2,055 (Covered by your annual dues)
What to Expect This Summer
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Surveying: Before any treatment, the state conducts a "Pre-Treatment Survey" to map exactly where the milfoil is.
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Notification: If your shoreline is scheduled for herbicide treatment, you will see yellow posters on your property with specific (usually 24-hour) water-use restrictions for irrigation or drinking.
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The "Clean, Drain, Dry" Rule: Even with these treatments, new milfoil can be introduced every single day at the boat launch. This is why our Lake Host program is so vital.
📣 The "300 vs. 100" Reality
While we have a plan and we have the funding for the professional bills, the SLA is still struggling with operational support. We have over 300 homes on this lake, but fewer than 100 have paid their dues.
Annual Dues start at $25.00. This money doesn't just go toward the milfoil; it pays for the UNH water testing that monitors our clarity and phosphorus levels, our insurance, and the administrative work required to secure these $20,000 town commitments.
Without the Association, there is no grant. Without the grant, there is no treatment. Without treatment, there is no lake.
How You Can Help Right Now:
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Don't Boat Through It: If you see a patch of weeds, go around. Your prop will chop it into fragments that will spread the infestation.
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Watch Your Wake: High wakes can break fragments off shallow-water milfoil.
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Sign Up to Volunteer: We need Weed Watchers to help us find the patches before the state surveyors arrive!
What is Milfoil?
Milfoil is a submerged aquatic plant with fine, densely packed, feather-like leaves whorled around a main stem. It can grow up to 15 feet and may exhibit a three- to six-inch green spike-like flower above the waterline in late June or in July. A cross-section of the stem will reveal “pie-shaped” air chambers. This exotic species of milfoil has been in the state since the late 1960s, and can currently be found in over 75 waterbodies in New Hampshire. There are six native milfoil species present in the state that do not cause problems, as they are low growing and do not form monocultures, unlike variable milfoil. Eurasian milfoil is another non-native milfoil found in New Hampshire, but it is less of a threat than variable milfoil due to our water chemistry (Eurasian milfoil tends to be found in waters with higher pH ranges than those found in New Hampshire).
How Does Milfoil Spread?
Boat propellers chop milfoil plants into small fragments. These fragments float on the surface and are at the mercy of the wind and lake currents. In a short time, roots form on these fragments. If washed ashore, these plants eventually take hold, creating a new colony of milfoil. The cycle goes on until every suitable area is filled in with these weeds. An alternative form of the plants develops during low water.
This vegetation type is more succulent than the submersed form and can persist for moderate periods of low water. NHDES has recently collaborated in a study to evaluate the viability of milfoil seeds and the research showed that milfoil seeds are very viable and have a high regeneration rate, though survival of the seedlings is thought to be relatively low. Regardless, seed production in a dense milfoil bed is high, and seeds are thought to be a probable source of new plants, even following extensive control measures (seeds are resistant to herbicides). Data suggest that long-term monitoring and appropriate follow-up activities are needed to truly reduce or potentially eradicate infestations. Regular surveys by NHDES biologists or volunteer Weed Watchers are needed to find new growth early, so that small-scale control measures can address the problem before it spreads.
It is unlikely that seeds are responsible for lake-to-lake spread; fragments are still the primary cause of that problem.
Information taken directly from NH DES Fact Sheet on Variable Milfoil: https://www.des.nh.gov/sites/g/files/ehbemt341/files/documents/2020-01/bb-23.pdf