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Wolfeboro makes major progress against milfoil

Limited chemical treatment planned for Sept. 15

September 03, 2009
WOLFEBORO — As the Wolfeboro Milfoil Control Committee completes the second full season of its five-year plan to eliminate variable milfoil from Back Bay, there is much to celebrate and a fresh reason to be wary.

According to Milfoil Committee Chair Ken Marschner, the combination of hand harvesting and limited chemical treatment has reduced the stands of milfoil in Back Bay substantially. Eight days of harvesting using a diver and a Diver Assisted Suction Harvester (DASH) this year removed 4,800 gallons of plants between June and August. This will be followed by treatment with the herbicide 2,4-D on Sept. 15 in the five areas indicated on the aerial view of Back Bay that accompanies this article.

Last year the entire area was treated with the herbicide, followed by five days of hand harvesting. Marschner says there are nine days of harvesting planned for 2010.

Harvesting with DASH, used for the first time last year, greatly improves results. The DASH is an aquatic vacuum cleaner used by divers to remove hand-pulled plants and their roots from lake bottom sediments. The suction from a boat-mounted pump draws the pulled material clear of the working area and deposits it into nets that collect the plants and roots while allowing the water to drain. Because the boat and pump are located well away from the area where the diver is pulling plants, the area stays clear of disturbed sediment, allowing the diver to see better and do a more thorough job of plant removal.

Hand pulling without DASH produced more limited results, since the disturbed sediment made it difficult to see how much of the plants remained.

Variable milfoil is a very aggressive plant that spreads quickly and puts down roots readily, driving out all native plants, so efforts to eradicate it have to be just as aggressive. Careful monitoring is also necessary to watch for spread.

On Aug. 6 the state Department of Environmental Services (DES) discovered isolated patches of milfoil in Wolfeboro Bay. While milfoil had been reported in Back Bay as early as the 1960s, there was no milfoil in Wolfeboro Bay in 1991, according to Marschner, and growth conditions in the harbor are not as favorable to milfoil growth as they are in Back Bay, where years of sawdust deposits from sawmills and the shallower bottom provide a substantial medium in which milfoil can thrive. Wolfeboro Bay is deeper and the wave action there is stronger, so putting down roots and staying in place is more difficult.

Having identified the milfoil locations (show in red in the aerial photograph on page A18), DES will next develop a five-year plan to remove it.

A long-term problem

Variable milfoil has been a growing problem throughout New England. Because it propagates so readily and spreads downstream, it is essential to take a comprehensive approach to eradicating it. Even though the state DES water division is involved in the process of developing environmentally-safe plans to control it, armies of volunteers, organized town by town or lake by lake are required to carry on the battle.

In Wolfeboro water flows from Lake Wentworth through Crescent Lake and the Smith River to Back Bay and then into Lake Winnipesaukee. Controlling milfoil thus has to involve all of these bodies of water, beginning with Lake Wentworth. Fortunately, the private Lake Wentworth Association (LWA) got involved and developed with DES treatment plans for Lake Wentworth, thus covering Crescent Lake and the Smith River as well. The LWA effort is one year further along on its five-year plan than that of the Wolfeboro Milfoil Control Committee for Back Bay.

The Wolfeboro Milfoil Control Committee was formed in 2005 with four goals: "1) limit the spread and reduce the harmful effects resulting from infestations of invasive aquatic plant species by managing and controlling those plants that cannot be completely eradicated; 2) educate Wolfeboro residents and visitors about the threat of invasive aquatic plants to the degree that they do not facilitate the continued multiplication of these plant through activities over which they have control; 3) prevent introduction of new invasive aquatic plant species into Wolfeboro's waterways that currently do not have the presence of those plants; and 4) purse sustainable funding to develop long-term programs to prevent the spread of existing invasive aquatic plant species and the introduction of new exotic aquatic plants."

Current members of the committee include, in addition to Marschner, Linda Murray (selectmen's liaison), Ralph Cadman, Skip Lorimor, Kurt Dietzer, and Bill Swaffield.

Marschner was the administrator of waste management programs at DES prior to his retirement. Since coordination with DES is crucial to the success of the milfoil program, having someone with his experience and knowledge on the committee has been greatly helped the committee meet its goals.

The program got off to a rocky start due to the abnormal floods in 2006 and 2007 that severely limited what could be done. The strong water flows and high water levels ruled out herbicide application. As a result, the variable milfoil in the Back Bay had more time to grow and establish itself. The January 2008 "Long-Term Variable Milfoil Management and Control Plan for Back Bay" prepared by DES stated that most of the 35-acre bay "had a variable milfoil percent cover ranging from 65-75+ percent with some isolated areas with growths that were less than 50 percent." The entire bay was targeted for chemical treatment with 2,4-D on June 5, 2008. That treatment was followed by five days of suction harvesting in August and October.

The chemical 2,4-D is encapsulated in clay pellets that are applied at the rate of 100 pounds per acre using a GPS positioning system that insures a uniform application. The pellets sink to the bottom of the lake, where the clay dissolves, releasing the chemical, which is taken up by the plants' root systems. By clearing away growing plants with the DASH system, remaining root systems are exposed to the chemical treatment, making that treatment more effective.

Water is tested 15 days following treatment. Following the 2008 treatment, water was tested by DES on June 23 and showed seven parts per billion of 2,4-D remaining. The standard for the Federal Safe Water Drinking Act for 2,4-D is 70 parts per billion, so the result was 10 times lower than the standard. By Aug. 15, 2008 the traces of 2,4-D were below the limits on the equipment used by DES for water analysis.

The DES 2008 plan allowed for treating up to 15 acres in 2009. Based on the major success of the 2008 efforts and the eight days of suction harvesting this summer, the area to be treated on Sept. 15 is smaller.

Looking forward

The five-year plan for Back Bay enters its third year next year and, according to Marschner, nine days of harvesting are planned.

Funding the milfoil effort is one on the committee's major challenges. While the Town of Wolfeboro contributes to the effort ($17,685 of the $39,000 budgeted for 2009), funds also come from the Abenaki Water Ski Club, the Lake Host program, and the New Hampshire Charitable Foundation. DES also has a grant program but, due to state budget problems, that source has been greatly reduced. For 2009 the DES Exotic Species Program provided a 30 percent cost grant for only the chemical treatment part of the plan, amounting to $3,145.50. According to Marschner, the Wolfeboro application was one of only 13 applications approved out of 33 submitted.

Now that milfoil has been detected in Wolfeboro Bay, a separate five-year plan for that location will have to be developed by DES, working with the Milfoil Control Committee.

"It's a continuous process," Marschner said. "You have to stick with it."

Martin Lord & Osman
Varney Smith
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