LYME — The Lyme Conservation Commission hopes that hand-pulling Eurasian milfoil will loosen the invasive plant species’ grip on Post Pond and make toxic herbicides unnecessary.
“We don’t like using toxins in the environment. That’s been the only method of treating the milfoil thus far,” said Sue MacKenzie, vice chair of the commission. “It has kept it down, but it’s not decreasing it at all.”
Eurasian water-milfoil, more commonly known as Eurasian milfoil, grows in “deceptively delicate” feathery stems, according to the U.S. Department of Agriculture. After it takes root in a lake bed, it grows into thick mats. It multiplies rapidly, blocks sunlight and chokes out native aquatic plants that fish and other underwater species rely on for food and shelter. As it spreads, it not only undermines biodiversity, but also makes swimming difficult and devalues waterfront property.
A New Hampshire Department of Environmental Services biologist and a volunteer monitor first found Eurasian milfoil in Post Pond in 2010, although it likely gained a foothold a year or two earlier, according to an NHDES report.
The first Eurasian milfoil arrived in North America in the 1940s, likely in the ballast of a ship, according to the USDA. Recreationists often unintentionally carry it on their boats. It spreads easily; just a fragment of its brittle stems can take root and create a new plant.
Over the last decade, Lyme has used herbicide to control Eurasian milfoil. But the wind that blows across the pond breaks up the milfoil, creating more fragments to take root and aiding its proliferation below the surface. The herbicides are not enough to stop its spread, and now it is around the whole perimeter of the pond, MacKenzie said.
The commission is recruiting volunteers to become state-certified divers to root out Eurasian milfoil. So far, about 15 people have indicated that they are willing to volunteer their time. The program will require boaters and divers, as well as monitors to mark Eurasian milfoil colonies.
But Lyme will continue to apply herbicides until there is a “significant decrease.”
“We need all hands on deck at this point,” MacKenzie said.
In its 2022 management plan, NHDES said it will continually evaluate whether herbicides are necessary each year.
Putting aside the environmental costs of plant-killing chemicals, volunteers pulling up the invasive species are a much cheaper option than hiring an NHDES subcontractor to apply herbicides. At Town Meeting, Lyme voters approved an article that appropriated $39,997 to manage Eurasian milfoil on Post Pond, with nearly $20,000 to be raised through a grant from NHDES.
Abandoning herbicides has a successful local precedent. The Lyme Conservation Commission is trying to “replicate the success” of the Mascoma Lake Association, MacKenzie said. That group has relied on a manual Eurasian milfoil strategy for over 25 years. Mascoma Lake provides the city of Lebanon’s drinking water, so herbicides were never an option, MacKenzie said.
“As coordinators of that effort for the past decade, we’ve seen genuine progress in reducing this invasive aquatic weed in our water,” wrote David Kelman and Martha Rich, who coordinate the program on Mascoma Lake, in 2021.
In 2020, they harvested “a mere 104 plants” — a steep decline since 2015 when they harvested 5,454 plants after introducing more intensive search methods. While they said the “trend looks good,” they warned that Eurasian milfoil can never be fully eradicated and advocated for continued vigilance: “Every plant that escapes our attention can swiftly become a new colony.”
So far, about 15 people have expressed interest in harvesting Eurasian milfoil on Post Pond, MacKenzie said.
“Anyone who harvests it needs to be trained,” MacKenzie said. Great care is needed because if any pieces of the plant float away, they may become the seeds of a greater infestation. The Conservation Commission will cover the cost of the NHDES training. Volunteers could fit their work into their free time.
On April 20, the Lyme Conservation Commission will hold an event for anyone interested in joining the effort. Its time and location are yet to be determined, but will be posted on the town website.
Claire Potter is a Report for America corps member. She can be reached at cpotter@vnews.com or 603-727-3242.