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  • Courtesy NH Department of Environmental Services

    This aerial photo of Lake Potanipo shows areas of milfoil infestation (red dots) and locations where herbicide has been applied (cross-hatched areas).
  • Courtesy NH Department of Environmental Services

    This aerial photo of Lake Potanipo shows areas of milfoil infestation (red dots) and locations where herbicide has been applied (cross-hatched areas).
Wednesday, September 15, 2010

Lake being treated for invasive weed

BROOKLINE – Swimming won’t be allowed for 24 hours in Lake Potanipo after herbicide is applied this morning.

Experts also recommend that boaters stay off the lake for two or three days to allow the treatment to take hold, although boating isn’t prohibited.

The procedure, being conducted from a boat, is similar to fertilizing a lawn: Technicians drop pellets that sink and dissolve, getting into the root system of the invasive weeds known as variable milfoil.

Variable milfoil, a scrubby-looking plant that resembles a bottle brush, grows on lake and pond bottoms, typically in the more shallow water near shore.

Uncontrolled, it can choke out aquatic life, eventually clogging a water body with a dense tangle of thick material that can be removed with chemical treatments, by hydroraking or by hand.

There is also a native milfoil found in the state’s lakes and ponds that scientists describe as “well-behaved,” saying it creates a healthy habitat.

On Sunday, Buddy Dougherty, chairman of the Conservation Commission, hosted a fact-finding tour on Lake Potanipo for a group of state lawmakers who represent area towns, enlisting Bob Bramley, who lives on the lake, to ferry the group in his pontoon boat.

Dougherty’s aim was to promote awareness of variable milfoil. But he also wanted to urge lawmakers to sponsor legislation that would fund milfoil removal and continued monitoring.

“You need someone to carry the banner,” he said, lamenting a shortage of volunteers and attention on the issue.

In some ways, it’s a tough sell.

For one thing, the invasive milfoil isn’t obvious until you get up close, whether swimming, fishing or riding in a boat.

For another, it’s hard to believe that lurking under a lake that looks as perfect as a scenic postcard, is something so terrible.

“You have to see, touch and feel to understand,” Bramley told the lawmakers riding in his boat.

Bramley and his wife, Kathleen, are unofficial Potanipo Lake stewards. Recently, they collected water samples for testing, and they spent summer evenings fishing near the shoreline and keeping an eye on the weeds.

Twice, Kathleen lost two bass that got tangled in milfoil, and she said that every time she goes out on the water, she checks to see if more fish are getting snagged by the weeds.

On Sunday, Dougherty predicted that prospects this week for a successful treatment were high, given the low level of the lake and the continuing drought.

Chemicals applied to milfoil are most effective when the water is still: heavy rain or currents would quickly carry the herbicide away from its intended target, he said.

Rain, or a storm, would have canceled the treatment.

“If it rains, the water current displaces the material,” Dougherty said, describing how the granules, applied like lawn fertilizer to the bottom of the lake, disperse and systemically kill the plant, starting at the roots.

The state owns Lake Potanipo while most of the property around it is owned by Camp Tevya, a private summer camp. There are also about 25 homes around the lake, including just one that is seasonal.

The town sells beach passes to residents every summer, and the boat launch is open to any boater, local or otherwise.

Officials say milfoil has been in the state since 1965, although it’s only recently that the plant has become a problem.

In 2002, according to the state Department of Environmental Services, there were a few rooted plants in several shoreline locations in Lake Potanipo. But DES biologists are predicting that over the next 10 years, the entire shoreline zone could be dominated with invasive weeds.

Dougherty said that’s why the Conservation Commission is taking $20,000 from its budget, earmarked for land purchases, to treat the milfoil in Potanipo.

He said local volunteers and a few paid employees inspected more than 1,000 boats this summer before they were put in at the lake and intercepted one boat, from Hudson, that was carrying fanwort, another invasive weed.

The town contributed $1,000 to run the education and inspection program, and the New Hampshire Lake Hosts Association chipped in another $750.

But there was a shortage of volunteers, and once the money ran out, the local program fizzled.

“Very few stepped up to the plate,” Dougherty said. “We hired college kids, but when the money ran out, they left.”

Still, there were some reasons to celebrate.

“They stopped the trailer (with fanwort) from going into Lake Potanipo,” Dougherty said. “That’s how milfoil got here. Someone with a dirty trailer.”

Dougherty and other conservationists say the more often boats are checked for milfoil, the higher the odds are of keeping it out of the lake.

But equally important, he said, is a buy-in from the public, through education and license fees for all boats, not just those with motors.

In addition, Dougherty suggested charging out-of-state boaters, who under a federal law are allowed to put in at lakes and ponds anywhere in the country for up to 29 days, without charge.

“Everyone wants the lake to be nice, but not on their nickel,” Dougherty said.

Brumley, the pontoon boat captain, said years back lakeside residents tried to organize a residents’ association. But there was little, if any, interest.

It’s still that way, despite the high stakes.

“There’s not a lot of physical support, people coming out and helping,” Dougherty said.

Hattie Bernstein can be reached at 673-3100, ext. 24, or