April 27, 2018
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Could an invasive weed threaten boating and fishing this summer?

By Heather Steeves, BDN Staff

With boating season comes the risk of infecting clean Maine lakes with invasive plants. These plants can overtake entire bodies of water, clogging them with dense, thick weeds that can render the lakes and ponds essentially useless for boating, swimming and fishing.

The invasive plants, which have no predators, are dangerous both environmentally and economically, as they deteriorate water quality, threaten tourism and sink property values, according to Roberta Hill, program director of the Volunteer Lake Monitoring Program’s center for invasive aquatic plants.

“They basically take over areas that were inhabited by native plants, and they can outgrow those habitats and become a complete monoculture,” Hill said.

Pieces of invasive plants from one body of water can stick to boat trailers or propellers, and when a boater travels to a clean lake and launches the boat, the plant takes root and spreads almost immediately.

Aquatic, exotic invasive plants include varieties of milfoil and hydrilla that can overtake a lake from shore to shore.

“They look like wet fields,” Hill said.

So far 32 Maine lakes have been infected, according to Paul Gregory, an environmental specialist for the invasive species program for the Maine Department of Environmental Protection. Of those bodies of water, 28 have milfoil, two have hydrilla, one has curly leaf pondweed and one has European naiad.

Gregory said the infected lakes line Interstate 95, which could indicate that the weeds are being brought in from out of state.

“People are able to travel more now than ever before,” he said. “The fact that folks can move their crafts over greater distance more quickly, it’s an opportunity for plants to hitchhike with these watercraft and move to new lakes.”

All of the infected lakes in Maine are located south of Knox County. That number is relatively low considering there are about 6,000 lakes and ponds in Maine and when compared with infestations in other states, but without some vigilance the invasive plants could spread north.

“Most other states in the country, if you ask them which of their lakes are infected, most all of them are,” Hill said. “Most other lakes in America are battling these aquatic invaders, but in Maine less than 1 percent of our lakes and ponds are known to be infected.”

Gregory said Maine is in one of the better situations in the nation, because the lakes are harder to get to, and there are so few infestations here so far.

The cheapest way to manage the invasive species is never to let them touch new water, Gregory said. The Maine DEP invests about $700,000 into invasive species work, with most of that money going into prevention.

Considering the $3.5 billion economic impact that camp owners, vacationers, fishermen and other lake users have on Maine each year, Gregory calls DEP’s annual investment “cheap insurance.”

“The prevention is so, so simple,” he said. “Bend over and look at your boat. It’s very simple to do.”

Getting people to do that, however, can be a “monumental challenge,” he said.

Hill and her army of more than 2,000 trained plant patrollers help out to protect Maine lakes by waiting for the plants at boat ramps and public landings and going after the plants as they try to hitch rides on boats, kayaks and canoes.

The volunteers and some paid workers look the vessels over carefully and remove any attached plants or seeds before they are launched into the water.

Gregory said this is Maine’s best defense against the plants.

“The most major environmental threat to Maine’s economy and Maine’s lakes can be prevented if people simply inspect their boats,” Gregory said.

Once a lake or pond is infected, the plant can seed. Or if a propeller chops part of the plant off, the chopped plant fragments can root. Eradication becomes difficult and costly, according to Hill.

Once a lake is overtaken, some methods of controlling the invasive plant include placing black mats over infected areas to kill the plants by starving them of sun, sending divers into the water to pluck the plants or using vacuum machines to suck the weeds up.

The Little Sebago Lake Association, for instance, reports spending $50,000 each summer to pay diving crews to use a suction machine to pull milfoil out of the lake, which is located in Windham and Gray.

But Hill stressed, “If we can keep the invaders out, one lake at a time, we can do the most cost-effective thing going.”

The Volunteer Lake Monitoring Program’s center for invasive aquatic plants will hold plant patroller training sessions throughout the summer.

The Liberty town office will offer a free session 2:30-8:30 p.m. July 20.

For information visit maine.gov/dep or mainevolunteerlakemonitors.org.

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