Lake George commission eyes weed killer that worked on Minerva Lake

By Gwendolyn Craig

The Lake George Park Commission is considering a new herbicide in the fight against an invasive and pervasive plant, Eurasian watermilfoil.

The herbicide was used for the first time in the Adirondack Park last year on Minerva Lake in Essex County. Leigh Walrath, freshwater analyst for the Adirondack Park Agency, gave commissioners an overview of the herbicide application at their April 27 meeting.

“I’m not advocating for this product anywhere,” Walrath said. “This is just what I see.”

What Walrath and Minerva town officials have seen so far is progress in the fight against the lake-clogging weed. With 8.73 gallons of ProcellaCOR EC applied to 41 acres of Minerva Lake, no Eurasian watermilfoil was found by the end of October, about 20 weeks after application. Herbicide concentrations declined as predicted, too, throughout the water body.

The Lake George commissioners have not committed to trying the treatment on their lake, but staff members will identify possible sites for a pilot project there.

ProcellaCOR EC is different from other herbicides that have been approved for the Adirondacks in the past. In 2013, an herbicide treatment called Renovate was used on Loon Lake. That involved using 1,200 pounds of the product, versus 8.73 gallons of ProcellaCOR EC. The concentration of this new herbicide is well below state Department of Health drinking water standards.

ProcellaCOR EC mimics a plant growth hormone that gets applied via spray or drip line off the back of a boat. Once milfoil takes it up, Walrath said, the chemical disrupts the plant’s growing process and ultimately kills it.

It has all been positive news for the town, which has watched Minerva Lake become choked with milfoil over the years. The town originally hand-pulled the invasive plants from the water, starting in 2007, and got the milfoil population so low that its lake managers recommended taking a break.

It was a costly mistake to stop harvesting, however, and the milfoil population skyrocketed soon after. In 2015, the town switched to what’s called diver-assisted suction harvesting. Divers collect the aquatic invasives and push the plants and roots through a suction hose that spits them out onto a boat. The harvesting cost $50,000 in 2015 and $75,000 in 2016, which Walrath said “is a very large amount of money for a 79-acre water body.” The herbicide treatment cost about $27,000, which included the permitting and monitoring, Walrath told commissioners.

The town still plans to conduct milfoil surveying and harvesting if needed this year. Walrath said the APA will follow up with the town to see if the herbicide is still keeping the worst of the milfoil at bay. Overall, he said, the APA has determined that the herbicide did clear out Eurasian watermilfoil over the entire water body, though the weed is not considered eradicated. The APA did not find that the herbicide had any negative effects on native plants.

Walrath said the treatment should last through 2022. The APA does not consider an invasive species eradicated unless a water body can go at least three years without any observations.

Joe Stanek, a Lake George park commissioner, asked Walrath and Park Commission Executive Director David Wick if the herbicide could be used in one of Lake George’s bays that is heavily concentrated with milfoil.

Wick said “there is merit” in having a conversation about the herbicide and that he and staff are going to survey potential test sites. He would come back before the board to see if commissioners wanted to move forward with a pilot.

Ken Parker, a park commissioner, asked about any long-term studies of the herbicide. Parker pointed to how the General Electric Co. contaminated area water bodies with polychlorinated biphenyls, or PCBs, once thought safe.

Commissioner Cathy LaBombard said a friend of hers lives on Minerva Lake and has seen the vegetation outside her dock disappear since the herbicide application. LaBombard worried, too, about whether the herbicide would harm waterfowl or cause any lasting problems.

Walrath referenced studies showing that the chemical did not have an adverse effect on wildlife at the concentrations being applied. He pointed to how the U.S. Environmental Protection Agency and New York have both approved the herbicide’s use. States including New Hampshire, Maine and Vermont have used the herbicide, and Walrath said he is in touch with counterparts in those states about longer-term surveys.

“As time does go on, we’ll learn more and more about it,” Walrath said.

LaBombard asked if the APA was going to continue monitoring Minerva Lake. Walrath said he plans for an informal survey this summer, but there is no APA regulatory requirement to conduct additional surveys or do any additional reporting.