Battle against milfoil continues at Lake Iroquois

Invasive milfoil hampers activities at Lake Iroquois. Photo by Rogo Senior
Invasive milfoil hampers activities at Lake Iroquois. Photo by Rogo Senior

It’s been the site of many a beach day and family picnic. But too often this summer, folks showed up at Lake Iroquois, got  a look at the dense green tangles below the surface, and left.

Eurasian milfoil, an invasive plant species that was first found near Lake Iroquois’ boat launch in 1990, is taking over. Spread easily among waterways on boats and fishing gear, “milfoil’s really become the dominant plant in the lake, and it’s really creating a monoculture in the lake,” notes Lake Iroquois Association (LIA) Director Jamie Carroll.

Carroll, who leads the LIA’s milfoil working group, describes the lake as a place of both ecological and economic importance. Lake Iroquois and tributary streams provide habitat for various animals, including amphibians that breed in fresh water, notes Carroll. Waterfowl and beavers make use of the lake, of course fish live there, and a nearby forest is home to deer, bear, and other large animals.

And the economic importance of the lake to its hosting towns is also considerable. Hineburg’s waterfront homes on the lake value over $22 million dollars, and contribute over $485,000 dollars in taxes annually.

The lake’s users typically include both homeowners and day visitors, but in addition to people arriving at the beach, taking a look (or a whiff), and leaving, the LIA notes a reduced use of the fishing access this year, notes Carroll.

The natural lake was dammed at one point, raising its level, but as a fairly shallow body of water, Lake Iroquois is a good place for milfoil to thrive, Carroll says. Nutrient inputs to the lake could also have contributed to the current problem.

A 1984 survey of aquatic plants in the lake found 45 species; in 2012 the lake only hosted 35 species, and by just two years later, another two species could no longer be located. Plant species are being lost over time as milfoil advances. Currently, says Carroll, milfoil occupies about 70 acres, out of 105 acres of the lake that could support the plant. Further milfoil expansion is therefore possible unless preventive measures are taken. This summer, suction harvesting of the milfoil took place at the lake – the first attempt at milfoil control there. On a small scale, for example along personal waterfronts, benthic mats laid on the lake’s floor prevent milfoil growth, but are pretty nonspecific in their impact; other species are affected by the mats, too. The use of these mats is limited by the state, and they can only be used when fish aren’t spawning.

Although invasive milfoil is a persistent and challenging problem, most of Vermont’s lakes and ponds remain free of milfoil infestation, says Carroll. And “that’s one of the things we hope to prevent, is other infestations.” To this end, a boat wash station complete with high-pressure spray will be installed at the lake’s fishing access, to stop invasive species from entering or exiting the lake.

And according to LIA’s website, since 2009, greeters, both paid and volunteer, have been on-hand at the fishing access to educate lake users about invasive species, and offer a free voluntary inspection of their boats and gear to prevent introduction of invasive species into the lake – or transport of such species out of Lake Iroquois. Results of these control measures will be published on the LIA website, says Carroll.

The costs of not addressing the milfoil problem are multiple, he adds: “The ecological costs will be reduced diversity of the plant community, which will then impact the other communities, whether it’s the fish communities or the algae communities.” And studies from the New England region indicate that infestations like these can decrease surrounding property values by 10-40%. “We may already be seeing some of that, or it certainly could get worse if the infestation is left uncontrolled,” Carroll notes.

At a public information meeting about the milfoil issue last week in Williston, many voiced their worries about the lake’s future.  Carroll understands their concern for a place that means a great deal to them. “My sense is that people around the lake love the lake and they want to improve the water quality for their use and for the use by others,” Carroll observes. “That’s the sense I’ve gotten.”