Lake George groups at odds over plan to use herbicide that targets milfoil

By Dana Holmlund

The Lake George Park Commission (LGPC) is seeking Adirondack Park Agency approval to trial the herbicide ProcellaCOR EC in two dense patches of invasive Eurasian watermilfoil in Lake George. After years of milfoil management, the expense is adding up and the results are discouraging. Park commissioners believe ProcellaCOR is the solution they’ve been looking for. Other environmental organizations are not so sure. 

The two treatments would test the effectiveness of the herbicide in Lake George and, if successful, mark the beginning of an integrated milfoil management plan. The targeted infestations are both on the lake’s east side, in Blair’s Bay and Sheep Meadow Bay near Huletts Landing. (Due to town boundaries in the lake’s waters, both applications go through town of Hague.)

For over three decades, LGPC has used various methods to quell the invasive plant in Lake George, such as diver-assisted suction harvesting—where divers uproot the milfoil and feed it through a vacuum tube to be ejected onto a boat—and laying benthic mats to smother growth. Residents and businesses have seen boating, angling and swimming hampered by stands of invasive milfoil clouding the water. In 2021 nearly 68 tons of milfoil were removed from the lake, according to the Lake George Park Commission’s website.  

Historically, annual management in Blair’s Bay has averaged $15,000-$20,000 per acre, according to the park commission. In contrast, the ProcellaCOR pilot treatments average $8,000 per acre. Executive Director David Wick said in a March meeting that the park commission believes ProcellaCOR is a cost-effective and ecologically beneficial solution to be used in “areas that have not responded well” to conventional management practices. 

The LGPC is encouraged by the success of the only other Adirondack lake to be treated with ProcellaCOR. The town of Minerva struggled to suppress the Eurasian watermilfoil problem in its lake until in 2020 the APA granted their appeal to use the herbicide. There, a stretch of 41 acres was dosed with 8.73 gallons of ProcellaCOR. Within two weeks the milfoil disappeared. No Eurasian watermilfoil growth, save for a single stem, was found in a plant survey of Minerva Lake last summer administered by SOLitude Lake Management. Non-target plant growth rebounded, and three new species were identified. 

Questions about safety

Still, some environmental organizations have reservations about the use of an herbicide that has been registered by the EPA only since 2018. 

The Lake George Association (LGA) feels ProcellaCOR is not a proper management tool for the lake. Chris Navitsky, LGA waterkeeper, believes there is a lack of conclusive research regarding ProcellaCOR’s full and long-term effects on native species including insects and other small animals that live at the bottom of the lake. He points to the EPA’s registration for the active ingredient in ProcellaCOR, florpyrauxifen-benzyl, which reads, “For freshwater benthic invertebrates, the submitted study showed toxicity at all of the levels tested, resulting in uncertainty regarding what level of [ProcellaCOR] in the environment would be below the threshold for toxicity.” 

The EPA review describes ProcellaCOR as effective at much lower dosages and with minimal non-target impacts when compared to older herbicides. The maximum application rate permitted is far lower than the contaminants allowed for in the New York State Drinking Water Standard. 

Risk to native plants 

Though it might be safer than its predecessors, ProcellaCOR still harms other species besides Eurasian watermilfoil.

Native milfoils showed they were nearly as sensitive to ProcellaCOR EC as Eurasian watermilfoil, according to a technical summary by environmental management firm SePro. Several kinds of water lily, including watershield and yellow water lily, also had temporary reactions to the herbicide. While there are no species of water lily in the pilot sites, there is a native milfoil. 

Alternate-flower watermilfoil (Myriophyllum alterniflorum) was detected in Blair’s and Sheep Meadow bays, initial plant surveys found. M. alterniflorum is on New York State’s rare and endangered species list and is common in Lake George. In response to concerns about native milfoil, Wick said in the March meeting that the DEC was not worried the ProcellaCOR pilot applications would wipe out native milfoil from the lake. He said the treatment covers 4 acres in a lake of 28,000 acres, and that annual surveys following ProcellaCOR application will check for native plant regrowth.  

The LGA does not share the park commission’s confidence. Navitsky reads from the EPA permit registering ProcellaCOR as an herbicide to be used in “slow-moving/quiescent waters with little or no continuous outflow”—a description he says does not match Lake George, which is a deep oligotrophic lake. He fears the current would disperse the herbicide far beyond the confines of the treatment sites. Navitsky says the absence of Eurasian milfoil in the entirety of Minerva Lake—not just the areas dosed with ProcellaCOR—proves the herbicide cannot be isolated in one place. He worries about the consequences to non-target species and says even though native milfoil is widespread in Lake George, it is still endangered and should be protected.  

The LGA’s claim that ProcellaCOR will cause harm by spreading throughout the lake, the Park Commission said, does not consider the fact that the herbicide would become highly diluted in lake water. As for concerns about ProcellaCOR’s suitability in the moving waters of the lake, the park commission emphasizes the pilot sites have been visited and approved by APA and DEC staff, as well as a member of SOLitude Lake Management. 

Navitsky, the waterkeeper, is not alone in his concerns. 88% of the comments submitted during the APA’s public comment period spoke against ProcellaCOR use in Lake George. Commenters say they feel there are too many unknowns to justify applying the herbicide without further study. Many commenters worry the herbicide will compromise drinking water supply and harm the ecosystem.

Adirondack Council Director of Communications John Sheehan said until there is robust evidence proving the herbicide is safe over the long term, the Council will continue to support things like more vigilant control of boat launches instead. “It is unlikely that you will hear an endorsement for any herbicide chemical treatment from the organization just because of our long-term concerns over long-term impacts,” Sheehan said. “There are no pesticides or herbicides that are considered to be 100% safe by any government entity.”

The Adirondack Lakes Alliance supports the Lake George pilot treatments. Executive Director Scott Ireland says the decision to hand-harvest or use ProcellaCOR isn’t “an either-or solution. It’s all part of a comprehensive solution to fighting this.”

Likewise, Wick told commissioners at a municipal briefing in March, “We’re not looking to replace our current diver-assisted methods solely with ProcellaCOR,” and that the herbicide is “another tool in the toolbox.”

The DEC has already granted the park commission a permit to use the herbicide. Now the commission awaits the APA’s verdict. The decision is likely to arrive at the next APA meeting on Thursday. Following endorsement, application would occur in early June of this year. With a treatment area of approximately 8 acres, the process should be completed in a single day. 

Dana Holmlund holds a degree in environmental studies and creative writing from SUNY Potsdam and is interested in the interaction between science and human society in the Adirondacks. She enjoys reading, outdoor recreation, and playing music.

Editor’s note: This story has been updated to clarify the proposed herbicide test site locations and to correct references to the park commission.