‘I’m encouraged’: Minerva Lake herbicide shows promising results

By Gwendolyn Craig

An herbicide used to treat invasive Eurasian watermilfoil for the first time in the Adirondack Park appears to have worked and could be used in other water bodies, though state officials say it’s too soon to say for sure.

The 79-acre Minerva Lake in Essex County has been battling milfoil since around 2007. Milfoil is a frustrating aquatic invasive species. It grows quickly, grows new plants from fragments, outcompetes native plants and turns lakes into swampy areas. It’s bad for the ecology and biology of the lake, but it’s also bad for boating, swimming and fishing.

David LaBar, a town councilman and owner of a rental cabin business on the lake, said the town has used various harvesting methods over the years.

The town typically spends about $70,000 a year on diver-assisted suction harvesting. That is where divers pull up the milfoil from the roots and shoot it up a vacuum hose onto a boat.

Harvesting milfoil is a bit like the Greek myth of Sisyphus, eternally rolling a rock up the hill, only to have it fall back down. Similarly, the milfoil always comes back.

But in May, the Adirondack Park Agency approved the one-time use of a new herbicide called ProcellaCor EC to add to Minerva Lake’s milfoil-fighting arsenal. The herbicide was registered with the U.S. Environmental Protection Agency in 2018 and approved for use in New York in 2019.

Solitude Lake Management, the contractors hired to perform the herbicide application, spread it in Minerva Lake on June 5. The management company has a GPS grid of where the dense milfoil beds are located. They targeted the herbicide using drip lines off the back of an air boat.

At first, LaBar said he couldn’t tell if it had worked. The problem weeds still poked up from the lake bottom almost two weeks after the application. But by about 2 ½ weeks, they disappeared.

“I would say we got the intended results, and perhaps a little more out of the application of the herbicide,” LaBar said.

Glenn Sullivan, of Solitude Lake Management, called the application “excellent” adding that “the native plant community was thriving.”

Sullivan and the APA have conducted a preliminary look at how the treatment went, and a spokesperson for APA confirmed that the milfoil “was cleared from the treatment area.”

“As expected, nearly all Eurasian watermilfoil stems have dropped from the water column and those that are still present have a blackened appearance,” the spokesman added.

There’s more monitoring to do, however. Milfoil does a good job of growing a strong root system and the APA will periodically monitor the treatment through 2021 and beyond.

So will ProcellaCOR be a solution for other lakes in the Adirondacks?

An APA spokesperson said “the Agency believes it is premature until future surveys and monitoring are completed.”

The APA did highlight how the herbicide has its positives. For example, it only needs low concentrations, it targets milfoil and avoids harming most native vegetation. The chemical also has a short lifespan in a waterbody. The APA also said there were no wetland impacts downstream of Minerva Lake at its sample locations.

“We had some resistance,” LaBar said, about originally pursuing use of an herbicide. “It’s like, ‘Geesh, chemicals.’ … But, (ProcellaCOR) checked all of our boxes for effectiveness and had low impact on human and animal life, so we were excited to give it a go.”

LaBar said the town is hoping the herbicide will have an impact for 2-3 years but they will continue hand-harvesting in the interim.

The herbicide application cost about $25,000, which includes the initial plant survey, the application, permitting measures and the follow-up surveys.

“I’m encouraged,” LaBar added. “I hope it’s promising for the entire Adirondack Park.”