Freedom – September 3, 2008 – Danforth Pond could be virtually milfoil-free, at least temporarily, if state and town officials implement an aggressive herbicide treatment of the non-native weed, according to DES limnologist and invasive species specialist Amy Smagula.
Smagula was the speaker at a Labor Day weekend meeting attended by Freedom town officials and lakefront property owners to discuss options for controlling the spread of variable milfoil in the hourglass-shaped body of water that connects to Broad Bay through Danforth Brook.
Topping the state’s list of options is treating the slimy invaders with the herbicide 2,4-D, which is the only approved aquatic chemical that attacks milfoil’s root system. The proposed treatment would be followed by selective hand-pulling by professional divers and the installation of a small number of benthic barriers, which are fiberglass mats that smother the pest by blocking sunlight.
Smagula said the state could pay up to half of the $14,000 cost but cautioned that the application process is competitive, noting that funding requests are usually three times higher than the state’s annual $110,000 budget.
Selectman Les Babb said the town would consider closing the money gap from its milfoil control fund if a majority of property owners supported the state’s recommended plan. Asking for a show of hands, Babb counted 43 votes in favor and 1 opposed.
The herbicide treatment is part of a DES management plan for the pond based on data compiled by the state and volunteers from the Friends of Danforth Pond and Ossipee Lake Alliance. While herbicide treatment is only one of number of options, Smagula said DES had ruled out most of the others. Milfoil-munching weevils will only eat the Eurasian variety, and dredging and mechanical harvesting could make the situation worse. She said the hand-pulling of thousands of pounds of weeds by professional divers during the past three years has been successful but has had limited impact.
“There’s no way divers can pull 24 acres of weeds all at once,” she said, “and the milfoil is spreading faster than it can be eliminated by hand.”
Asked about the safety of 2,4-D, Smagula said the chemical is safe “when used appropriately.” To create a margin of safety, she said the state works with just two professional contractors and has established application and post-application safety standards that exceed the product’s directions for use. She said state tests have shown 2,4-D, which is broadcast using dissolvable pellets, does not migrate into ground water and is safe for fish and native plants.
Introduced in the 1920s 2,4-D has been used to control invasive weeds in New Hampshire lakes for more than 40 years and has been used in all of the New England states, especially Massachusetts and Connecticut where milfoil problems are similar to New Hampshire’s.
“Maine and Vermont have less milfoil and are more restrictive in their use of herbicides,” she said, “although Maine has used it to control hydrilla, which is even more aggressive than variable milfoil.”
Asked about controlling shoreline runoff as part of the plan, Smagula acknowledged that the pond’s thick layer of sediment is an ideal breeding ground for milfoil, but said the weed is so adaptable it would continue to spread even if the bottom were sandy. She said reducing the pond’s nutrient load should be part of an overall watershed management plan that includes “limiting development and encouraging smart growth.”
If approved, Danforth Pond’s milfoil control plan will not be the first time an aquatic herbicide has been used in the Ossipee Lake system. Diquat, which kills invasive plants but not their root system, was used in Danforth Pond in 2002 and subsequently in Phillips Brook and Leavitt Bay in Ossipee. In all three instances the weeds returned in full force the following year. In contrast, Smagula says 2,4-D will knock the plants back for 3-5 years, making follow-up control methods, like hand-harvesting, more effective.
Long Term Issue
Hovering over the meeting was the reality that Danforth Pond’s milfoil issue is a permanent one. While no one knows how the indestructible weed entered the pond, biologist and long-time lake resident Barre Helllquist said he believes the weed has been an unwelcome resident since the mid-1980s.
Several members of the audience asked why the state continues to fund new boat ramps providing unmanaged access to state lakes while underfunding milfoil control. Several others suggested that businesses bringing boats to the lake should pay more of the control cost.
Friends of Danforth Pond spokesperson Marcia Murphy said more than $90,000 has been spent to date. She and Selectman Babb said Danforth Bay Camping Resort had paid a large part of that amount, and Ossipee Lake Alliance director David Smith added that the campground has an excellent record of educating their boaters about milfoil.
Babb asked that a formal request for town financial support be submitted by September 9 to meet the state’s funding application deadline of September 15. Comments on the plan can be posted here or addressed to DES at firstname.lastname@example.org.