You can rip them out, poison them, vacuum them up, or smother them with sheets of plastic, but your chances of eradicating the exotic plants that are invading the region’s ponds and lakes are slim, according to environmental officials.
“Once they are in your lake, you are very unlikely to get rid of them,” said Anne Carroll, director of the Office of Water Resources in the Massachusetts Department of Conservation and Recreation. “You just have to deal with them — like mowing your lawn.”
About a third of the approximately 3,000 freshwater lakes and ponds in the state are affected, according to Tom Flannery, who runs the department’s Weed Watchers Program that trains people to spot and report invasive freshwater plants.
Winter Pond in Winchester is battling milfoil, and Martins Pond in North Reading is fighting fanwort. Water chestnut is clogging the Mystic River in Medford and Somerville.
“These invasives are called invasives for a reason,” Flannery said. “You can take a crystal-clear water body and introduce [an invasive] plant, and literally the entire lake is covered top to bottom with weeds. You can’t fish, you can’t boat, you can’t swim, the wildlife suffers. [The time ] varies depending on things like lake chemistry and depth. But I’ve seen a lake go from zero to 40 acres in one growing season.”
That does not mean it is time to give up the fight, however, both Carroll and Flannery said.
“It still makes sense to find things early and have a chance to save the lake,” Flannery said. “Even if you have a lake chock full of invasives, you haven’t lost the battle. The key is management. You have to work at it year after year — and spend a lot of money.”
He said the state spends about $500,000 annually on the battle, and municipalities and private associations spend about another $1.5 million .
While Flannery said the figure is not close to what is needed, both he and Carroll are encouraged by a new state law that requires the Department of Conservation and Recreation to write rules to combat the spread of invasive species and impose penalties for those who fail to comply. The regulations should be finished by the end of the summer, and will focus on requiring people to clean their boats, Carroll said.
“It’s pretty basic,” she said. “When you come out of a lake with invasives, look at your boat, at the motor, props, the trailer. A quick visual check should take care of it. Or run it through a car wash, or let it dry. We also ask people to empty out anything they filled with pond water and dump it on the ground far enough away that it won’t get back in.
“It’s not onerous, and it is now the law,” she said. “There certainly are people out there who feel fatalistic about this problem, but we’re not. . . . I think we’re keeping up; we actually feel a little bit hopeful.”
One place of optimism is Lake Attitash — 360 acres of water spanning the towns of Amesbury and Merrimac — where milfoil was rampant until the Lake Attitash Association raised $100,000 to treat the invasive weed with herbicides last summer, according to board member Ron Klodenski. By late fall, the weed was “pretty much eradicated,” he said.
To protect the investment, 25 volunteers trained as “weed watchers” patrol the lake regularly. Unfortunately, this summer they discovered a patch of milfoil in a secluded cove, Klodenski said. He said the association is deciding how to handle the new crop; suggestions include laying a mat on the lake bed to smother the plants.
“We were quite disappointed to find the milfoil in that little section,” he said, “but it looks like our weed watcher program is working. The lesson is if you get some dedicated volunteers who are willing to do the work, you can deal with it.”
Since 2010, volunteers in kayaks and canoes have been out on the Mystic River, dealing with water chestnut. The invasive plant forms thick, fluffy green mats on the top of freshwater bodies and chokes out all other vegetation. In a single season, an acre of water chestnut can produce enough seeds to cover 100 acres of water the following year.
“It’s a pretty big problem; it really impairs the river for recreation and for its ecological value,” said Patrick Herron, water quality monitoring director for the Mystic River Watershed Association, based in Arlington.
Water chestnut “probably covers 60 percent of the river,” he said. “In some places, it’s covering everything but a narrow channel where boats with a propeller have chopped their way through. In other areas, after three years of work, we’ve made some major progress.”
In addition to physically removing the plants, the watershed association is also working with communities to decrease the amount of storm water going into the river.
“The real problem is the amount of nutrients — especially phosphorus — that get into the waterways and fuel this plant growth,” Herron said.
In Winchester, the Conservation Commission approved herbicide use in Upper Mystic Lake to kill milfoil and other weeds, with the condition that educational brochures be mailed to residents to suggest ways to reduce the amount of lawn fertilizer flowing into the 200-acre lake, according to conservation administrator Elaine Vreeland.
The commission also has allowed regular herbicide use on 17-acre Winter Pond since 2007, and it approved the release of 10,000 purple loosestrife-eating beetles there in 2001, she said.
“That worked very well,” Vreeland said. “It took a couple of years, but eventually [the beetles] ate back the purple loosestrife, which is a terribly invasive and aggressive plant.”
In North Reading, the Martins Pond Association also used beetles to control purple loosestrife, and did hydro-raking — similar to running an underwater lawn mower — to combat the weed fanwort, said the organization’s cochairwoman, Janet Nicosia.
The reduction in the loosestrife population was dramatic, she said, while the amount of fanwort ebbs and flows.
“I heard from one member who’s out on the pond every day that the fanwort is pretty thick right now. I don’t know if we’ll have to do another hydro-raking,” she said.
Nicosia said users of the 92-acre pond also are watching out for water chestnut. When spotted, the plants have been yanked out by hand over the last few years.
Carroll said that steps to educate the public about the plants are essential. Another priority is to make sure that weeds stay out of uncontaminated waters such as Walden Pond.
“Some are pristine, and it’s our priority to keep them that way,” she said.Johanna Seltz can be reached at firstname.lastname@example.org.