In New Hampshire’s battle against invasive species, the state has long treated its lakes and ponds with herbicides.
The applications are effective, but controversial, because of their potential long term environmental impacts.
So this past summer, the state has been testing a new tool that could reduce its reliance on chemicals.
New Hampshire Public Radio Correspondent Shannon Mullen reports.
MULLEN: (in field) Smith Cove on Lake Winnipesaukee is a quiet little inlet with dozens of homes along the shoreline, a pair of yacht clubs, and a boat yard. For the last few decades, it’s also had one of this Lake’s worst infestations of the underwater invasive species variable milfoil.
THARPE: I’m getting too old for this. This here’s cold water!
MULLEN: Well, it used to be a quiet little inlet, before Chuck Tharp and his business partner Mark Richardson got here.
They own Gilford Diver Services, and the state hired them to test the newest weapon in its fight against milfoil.
RICHARDSON: It’s an underwater vacuum cleaner.
MULLEN: …also known as DASH – a Diver Assisted Suction Harvester.
The DASH is a pair of small engines, each attached to a water pump and a 40 foot vacuum hose.
And the whole unit is mounted on bright red pontoons with an overhead canopy, so it looks like a party barge from a distance.
The divers take the hoses to the bottom of the shallow cove, uproot the milfoil plants by hand, and use the hoses to suck them up to the barge.
THARP: It’s not just grabbing these plants and pulling them. You have to get underneath, get the entire root ball out, and you find they’re intertwined with each plant.
MULLEN: (in field) Milfoil grows in shallow water, usually 6 to 12 feet where the sun can reach the plant. Under water it looks like one of those tube shaped brushes you might use to clean a fishtank filter, but when you pull it out… it looks like a green hairy weed with a flexible stem. It has thin green filaments growing off in every direction. And even a 2 inch piece of this plant can spawn a new one when it’s broken off by a passing boat, or inadvertently, a diver trying to get rid of it.
RICHARDSON: The idea is to fragment it as little as possible when it comes up from the bottom of the water here to the site where we’re going to dispose of it.
MULLEN: Richardson says harvesting milfoil by hand, without the DASH, can cause a lot of breakage, and it’s a much slower process.
RICHARDSON: A diver that’s down for an hour with a hand bag will come up with anywhere from 2 to 4 gallons of milfoil, and we’re seeing rates significantly higher, we’ll typically pull up 100 gallons in an hour and a half, with 2 divers.
MULLEN: Working for about 2 months, Richardson and Tharp have harvested more than 15-hundred gallons of milfoil from Smith Cove.
They’ve trained 5 other divers on using DASH so far, and the state plans to get more of these barges for other lakes.
But as effective as DASH is proving to be, the Department of Environmental Services says, it was chemical treatment that killed off most of the milfoil in Smith Cove.
D-E-S Exotic Species Program Coordinator Amy Smagula says herbicides are controlling populations of the plant around the state.
SMAGULA: We’ve seen a decrease in the rate of spread, we used to see 3 or 4 new infestations every year, and now we just don’t see that. It’s none or maybe just one…
MULLEN: D-E-S has been treating lakes and ponds with the agricultural herbicides since the late 1980s, sometimes several years in a row.
Smagula says the state restricts public water-use for 7 days after an application, much longer than product recommendations.
And she says the chemicals don’t pose a human health threat in the amounts used per treatment.
SMAGULA: There’s a lot of misconception out there, about the use of herbicides, and when they’re done correctly by licensed applicators, and they’re coordinated by people that are scientists that know what they’re doing, they’re safe, when done according to label restrictions.
MULLEN: But little is known about the chemicals’ potential long term impacts on wildlife and the environment.
So the state has a new plan: use herbicides once, then follow-up with divers and DASH for a few years to make sure milfoil doesn’t grow back.
And D-E-S says prevention will be key to whether the new plan works.
Its volunteer “Lake Hosts” educate boaters about milfoil at public launch sites, and “Weed Watchers” spot new plants and call in tips so the state can send divers before it spreads.
MORRISETTE: At one point out in front of the docks where we’re standing, the milfoil was so thick it was about 70 feet across, it was so thick it looked like you could walk on it. It was like a platform out there…
MULLEN: Smith Cove homeowner Peter Morrisette heads the Glendale Cove Association; most members are his neighbors.
The group and the state split the cost of treating Smith Cove with herbicides in May.
Morisette says he doesn’t like chemicals, but he’s happy with the result of the treatment, and even happier that the DASH could prevent the need for another one.
MORRISETTE: I’m not going to ever tell you there’s not one little piece of milfoil in the cove, but with any kind of luck, we can keep it under control and keep working at pulling it so it gets better and better each year.
MULLEN: Even some neighbors who fought the use of herbicides have backed off.
Retired chemist Joe Paterno was one of the most adamant opponents.
PATERNO: On the one hand earlier this year I was writing checks to our attorney to fight this thing, and about a month ago I wrote a check to the Glendale Cove Association in support of it… and if the plan continues to be implemented with …no more chemicals, I’m all in favor of it.
MULLEN: That might be possible now, says D-E-S’s Amy Smagula, with few, if any new infestations in New Hampshire each year.
She says the state has the spread of milfoil under control, but admits the list of 58 infested lakes is not shrinking.
Once a water body gets invaded, the milfoil is almost impossible to get rid of.
SM: (on tape) Do you ever feel like you’re on a fool’s errand with this stuff? It’s so good at getting where it’s not supposed to be!
SMAGULA: Sometimes you do feel like you’re on a fool’s errand with it, but there’s always new technology to try, and I haven’t given up hope yet, I’m still very optimistic. Milfoil has not won!!
For NHPR News, I’m SM.
