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War on milfoil resumes in state's lakes

Mark Richardson of DiveMasters Dive Services hoists a clump of milfoil onto his harvesting platform while a diver hand pulls the weeds from Lee's Pond in Moultonboro. Donna Rhodes. (click for larger version)
June 24, 2009
LAKES REGION — A growing problem in N.H. is again drawing attention as crews set out to tackle milfoil problems in the lakes.

Spring is an opportune time to begin the task of eradication of this noxious weed as plants have not yet grown to their full potential. The state Department of Environmental Services has targeted areas like Jay's Marina in Tilton to address through a five-year plan of weed eradication.

2-4d, a chemical component known to not just defoliate but spread to the roots of the plant, was sprayed at the marina's dock area earlier this month. It is the first step in attacking the problem when it grows out of control.

"It's a process," said state limnologist Jody Connor. "They sprayed on Friday and will go back and spray again later when they can move some of the boats out of the way to get underneath them, too."

The chemical disperses in the water column quickly, heading into the root system of the milfoil. Although bass have nested in the area, they leave when disturbed by the spraying and return later. Connor assured that the chemical does not affect them as a part of the food chain.

"This chemical (2-4 d) is an herbicide and we use such a low concentration of it in the spraying," Connor said. "It's taken up through the root system of the plant very quickly and kills it, especially the crowns."

Following the spraying, Connor said a crew would most likely be sent in to hand harvest some of the remaining plants.

Left alone, these weeds can be extremely detrimental to the aquatic environment. Some sportsmen claim it to be a boon to bass that nest alongside a milfoil field, which later provides shelter to their young spawn. Connor said bass populations can actually be harmed in the long run.

"The milfoil can actually take oxygen from the water and kill off other aquatic plants that are native to the area and used by the fish," he noted. "It can choke a small body of water."

Fighting milfoil isn't an easy task, as it can grow at the rate of an inch a day in the right conditions. Chemicals and harvesting are just a few of the battles in the war against the plant.

"Prevention," stressed Connor, "is the key. Keeping it (milfoil) out of lakes is very important. The next stage is to keep it from spreading."

A Weed Watcher Program instituted by the state has helped in keeping the problem in check. Volunteers are trained to identify milfoil and to report it to the proper officials but cannot try to hand harvest the milfoil themselves. Milfoil spreads by a process called "fragmentation." A small piece can drift off and begin to grow elsewhere, causing the infestation to actually spread. Currently it is against the law to pull milfoil without proper certification.

On local company certified for milfoil harvesting is DiveMasters Dive Services of Gilford. Owner Mark Richardson and his team have been instrumental in working with the state to develop methods for harvesting along with training other divers in the process. Richardson has modified a pontoon boat to serve as a milfoil harvesting platform for his crew.

"It's still a work in progress as we learn more ways to deal with the milfoil," Richardson said during a recent harvest on Lee's Pond in Moultonboro.

Simply put, he has set up the boat with a drainage net built into the flooring and a vacuum system. Certified divers like Jason McCarthy go underwater with the vacuum hose, pull the weeds and vacuum them up into the drainage net onboard the boat. Water pulls the weeds up through the hose, which then flows through the mesh bag and back into the lake. Richardson scoops up the weeds and transfers them into 20-gallon bags to be later disposed of far from the lakes where they thrive.

"You have to be careful not to stir up a lot of silt," cautioned McCarthy on a break from harvesting. "Silting is not good for a pond or lake either. We want to just get as many of the plants as possible without disturbing the bottom or the native plants in the area."

On an average day they can remove close to 300-400 gallons or more of milfoil. It's a labor-intensive job but works well in ridding the waters of the weed.

Removing the root ball is essential in clearing patches or fields of milfoil. Divers like McCarthy are trained to get all of the plant as they pull and deposit it in a bag or through a vacuum hose.

"Suction harvesting," said Richardson, "really puts hand-pulling in a new dimension. You can pull the plant and send it right out of the water quickly. Hand pulling is really an effective way to fight the problem."

DiveMasters was part of the clean-up effort in Gilford's Smith Cove in 2006. They put in many hours harvesting virtual forests of the plant.

"There were 12-foot tall plants coming up in the cove," Richardson said. "It was unbelievable, but it's much better now."

McCarthy said situations like that can be hazardous. The plants grow so tall and so thick that he said divers literally swim into darkness as they enter a field of milfoil. It can entrap and confuse a diver caught amidst the weeds.

Connor pointed out another downside to milfoil is its effect on lakeside property values. Should a waterfront property be encumbered with a milfoil infestation, it loses its desirability.

"Regionalization in fighting this would be helpful," Connor said, noting how some lakes encompass many towns along the shoreline. "The problem is with the economy. There isn't a lot of money out there to fight it."

Last year the state worked on the north end of Lake Winnisquam and money has been relegated to deal with milfoil in Sanbornton at their recent Town Meeting in May. Laconia and Tilton have funded spraying in the past as well, but the size of the lake makes an all-out effort unfeasible.

New Hampshire is not alone in dealing with milfoil, but is known for its proactive stance in handling the problem. A lot of time and effort is put into research and the state has been working with a scientific group in Florida to learn more about milfoil's components and methods used to address infestations.

New Hampshire has also developed the "Lake Host Program" to combat milfoil. Lake associations, concerned property owners and others are trained to monitor boat launches in their area. The common method of transportation for milfoil is by boats brought from one body of water to another. The slightest piece of milfoil entangled in a boat propeller is enough to create a new infestation. Still, the state urges boat owners to inspect their equipment before placing it in a body of water. Signs at launches alert them of their responsibilities in keeping the lakes clean and milfoil-free.

Interested citizens or groups can find out more about Weed Watchers and Lake Host Programs by going to www.des.nh.gov and click on "Programs."

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