After herbicide use, Lake George divers see desired results

Lake manager says 30-day look at bays treated with ProcellaCOR are showing dead milfoil, green natives

By Zachary Matson

Thirty days after the first chemical control of invasive plants on Lake George, divers assessing two bays treated with herbicide found dead Eurasian watermilfoil and growing native plants on the lake bottom, just as prescribed.

Staffers with the Warren County Soil and Water Conservation District on Tuesday joined Dave Wick, executive director of the the Lake George Park Commission, and a representative of the herbicide manufacturer for a 30-day-post-treatment qualitative plant survey at the two northern basin bays the commission used as demonstration sites for ProcellaCOR treatments that targeted the invasive milfoil.

Swimming across the demonstration sites, each about 4 acres in size, the team recorded native plants and their density. They also documented the state of milfoil within the sites, taking underwater photographs and videos. 

Most Eurasian watermilfoil was killed, completely deteriorated in some places and turned to little brown stems in other places.

At the Blairs Bay site, a dense milfoil bed on the northern edge of the treatment zone was still partly green but flopped over on itself. Wick’s group hoped the milfoil would die in coming weeks. 

The divers were buoyed by the presence of native plants in areas they had been previously and in areas once dominated by milfoil. The native plants support fish and other wildlife and the healthy functioning of the lake.

“Bringing back the native ecology, that’s exactly what the project is about,” Wick said. “Take the cancer out of the system and let the rest recover.” 

The Warren County divers will return for a formal quantitative survey in August, recording the plants found in locations also surveyed in 2021 using the same methods. That survey is required under the state permits approving the project. 

As it evaluates the outcomes of the June herbicide treatments — at Blairs Bay and Jeliffe-Knight Bay, near Huletts Landing — the lake commission is also weighing where, when and whether to use the herbicide next. 

Representatives of the Adirondack Park Agency plan to visit Lake George this month to assess three potential sites for the next herbicide treatment: Harris Bay in the southern basin; Sunset Bay, just north of Huletts Landing in the northern basin; and Hague Brook delta, also in the northern basin.

While the APA visit would be necessary for a permit for next year, Wick said the agency was still determining whether to wait longer before pursuing another herbicide application. 

“It’s still up in the air,” he said. 

A long and contentious process

Lake managers and advocates for nearly 40 years have worked to fight the spread of invasive milfoil in numerous bays throughout the lake, spending hundreds of thousands of dollars each year on hand-harvesting techniques. In 2021, the commission proposed testing ProcellaCOR, at the time a new product garnering increased interest for its targeted use against milfoil. But shortly after merging with the Fund for Lake George, the Lake George Association raised concerns that the product had not been studied enough and challenged the commission’s herbicide plan.

That challenge, both in the courts and the court of public opinion, and the commission’s commitment to its plan has driven a wedge between the state agency charged with managing the lake and the well-heeled nonprofit committed to its protection.

After years of litigation, a Warren County judge in June allowed the herbicide plan to move forward.

Opponents of the plan have argued that not enough is known about the long-term effects of its use on the environment and human health, despite government assurances that it’s safe. They said the consequences of the herbicide may not show up in initial water testing and plant surveys but will come to harm the lake. The LGA is conducting its own study of the demonstration bays, promising to release results of water sampling and plant and macroinvertebrate surveys. 

A closer look at the impact

On Tuesday, Nick Rowell, a natural resource specialist with the conservation district, and Jake Dunkley, a district technician, donned scuba gear and dipped under the water’s surface with waterproof checklists of native plants. They explored the lake bottom, checking off plants they identified along the way. They also filmed the underwater plant community to present to the commission and public at future meetings.  

“It’s wild looking down and actually seeing natives,” Dunkley said. 

They said there were clear lines of demarcation between where the milfoil beds had been and the areas populated by native plants. As they return to survey the plant community in future years, they expect the native plants to gradually start to fill in the areas once dominated by milfoil. Since milfoil grows taller than many native plants and forms dense beds, its absence altered the feel of the lake to the divers.  

“The bay feels so deep,” Rowell said.  

The team was also joined by Jon Gosselin, an aquatics specialist in the northeast for SePro, the company that manufacturers ProcellaCOR, and Bob Bombard, who has also surveyed milfoil and native plants before and after herbicide treatments throughout Warren County. 

Gosselin said the Lake George project has drawn more attention than most all proposed in the Northeast. 

He said he wasn’t aware of a project with as much water sampling for the size of the herbicide application. They pulled up over 15 different native plant species at Jeliffe-Knight Bay, spreading them across the boat deck. Swimming around the bay, they identified turtles and a handful of fish species, including sunfish, pumpkinseed, bass, northern pike, perch and others. 

Wick said he doesn’t expect to ever need to treat the two bays with ProcellaCOR again. The commission and the milfoil harvesters it contracts with will continue to check the bays for milfoil and remove any plants by hand.

Wick has said about a dozen bays around the lake would be candidates for ProcellaCOR use, areas with persistent and widespread milfoil infestations that have proved difficult to manage by hand. If the herbicide helps reduce the agency’s milfoil control budget, he said, that money can be shifted to green infrastructure, salt reduction, stream restoration, culvert replacements and other priorities. 

“All of those opportunity costs come back on the table,” Wick said. 

In nearby Sunset Bay, longstanding milfoil beds had grown up to a few feet from the water’s surface. The beds were thick with milfoil, which towers over other underwater plants. Small pockets of larger native plants squeezed into areas within the broader milfoil infestation, but many of the lower-lying native plants could not be seen from above.

Top photo: Native plants found in Lake George during an assessment of sites treated with an herbicide in June. Photo by Zachary Matson

Following our water resources

Keep up with Zach’s reporting by signing up for his free weekly “Water Line” newsletter