The Lake George ProcellaCOR lawsuit is a still-open legal fight in which the Lake George Association and a coalition of towns, a waterkeeper group, and lakeshore property owners have sued New York state agencies to stop the use of the aquatic herbicide ProcellaCOR in Lake George. The plaintiffs won an early ruling voiding the state’s first permits, lost on appeal in May 2024, failed to secure an injunction against a second round of permits later that June, and the herbicide was applied in two bays on June 29, 2024. A broader constitutional challenge filed in Warren County remains pending, and a September 2025 study on sediment persistence has reopened the underlying scientific dispute.
Why the Lawsuits Were Filed
Eurasian watermilfoil, an invasive aquatic weed, has been in Lake George since 1985. For decades the response was diver-assisted suction harvesting, and the Lake George Association has put nearly $2 million into hand-harvesting since 2009, spending up to $140,000 per year to manage about 40 sites annually.1Lake George Association. ProcellaCOR
In 2022 the Lake George Park Commission, the state agency responsible for managing invasives in the lake, sought permits from the New York State Department of Environmental Conservation and the Adirondack Park Agency to apply ProcellaCOR to two roughly four-acre sites in the town of Hague: Blairs Bay and Sheep Meadow Bay.2Lake George Association. ProcellaCOR Timeline SOLitude Lake Management, a Virginia Beach–based lake management firm, was contracted to perform the application.3News10. Lawsuit Filed to Prevent Use of Herbicide in Lake George
ProcellaCOR’s active ingredient is florpyrauxifen-benzyl, which mimics a plant growth hormone and is designed to kill milfoil while sparing most native plants. The EPA registered it in 2017 and New York’s DEC approved it in 2019.4Adirondack Explorer. ProcellaCOR Herbicide Explained Opponents argued that Lake George is atypical: an unusually clear, nutrient-poor oligotrophic lake that also serves as a drinking water source, and one that has never had chemicals intentionally introduced. The LGA also argued the product was designed for “calm and quiescent waters,” which it says does not describe Lake George.1Lake George Association. ProcellaCOR
The First Lawsuit and the Appellate Reversal
On May 12, 2022, the Lake George Association, Lake George Waterkeeper, the Town of Hague, and property owner Helena G. Rice filed a petition in New York State Supreme Court challenging the DEC and APA permits as arbitrary and capricious.2Lake George Association. ProcellaCOR Timeline The core legal claim was procedural. The petitioners argued that the APA should have held an adjudicatory hearing, a formal trial-like proceeding with expert testimony and cross-examination, before approving the permits. They also alleged the agency had not adequately considered hand harvesting as an alternative, had relied on a biased staff report, and had not properly assessed the risks of drift beyond the target bays or of harmful algal blooms.5FindLaw. Matter of Lake George Assn. v NYS Adirondack Park Agency
The trial court sided with the plaintiffs. On March 3, 2023, the New York State Supreme Court voided the permits, holding that the APA’s approval without an adjudicatory hearing was arbitrary and capricious.2Lake George Association. ProcellaCOR Timeline The Lake George Park Commission reapplied for permits, and the state appealed.
On May 2, 2024, the Appellate Division’s Third Department reversed. In Matter of Lake George Association v. NYS Adirondack Park Agency, the panel held that the APA has broad discretion to decide whether an adjudicatory hearing is needed and that the petitioners had not shown “substantive and significant issues” that would trigger one. Because the APA had not held a fact-finding hearing, the court said, judicial review was limited to whether the agency’s determination was rational, and a court could not substitute its own judgment.6New York Appellate Digest. Lake George Assn. v NYS Adirondack Park Agency, Third Dept The LGA said it would seek leave to appeal to the New York Court of Appeals.7Lake George Association. LGA Response to Appellate Court Ruling
The Second Lawsuit and the Failed Injunction
The state moved quickly after the appellate ruling. On June 20, 2024, the APA voted to approve new permits, with one dissenting vote from board member Zoë Smith.8Adirondack Explorer. Adirondack Park Agency Gives Go-Ahead to Herbicide in Lake George The DEC issued its pesticide permits the next day, opening an application window of June 26 through June 30.
That same day, a broader coalition filed a new suit in Warren County Supreme Court. The plaintiffs now included the Lake George Association, Lake George Waterkeeper, the Towns of Hague and Dresden, and six individual property owners. The suit sought to annul the new permits and permanently enjoin the herbicide’s use, invoking the Green Amendment to the New York State Constitution, which guarantees the right to a clean environment.8Adirondack Explorer. Adirondack Park Agency Gives Go-Ahead to Herbicide in Lake George The plaintiffs pointed to private water intake pipes inside the treatment zones as evidence of direct constitutional harm.3News10. Lawsuit Filed to Prevent Use of Herbicide in Lake George
The court issued a temporary restraining order on June 21, 2024, halting the application. It did not hold. On June 28, Warren County Supreme Court Justice Robert Muller lifted the restraining order, ruling that he “did not have the discretion to ignore agency determinations” and that the evidence did not support an injunction.9WAMC. ProcellaCOR Used in Lake George Following Warren County Supreme Court Decision The next morning, June 29, SOLitude applied ProcellaCOR in Blairs Bay and Sheep Meadow Bay, using roughly four gallons per site at a concentration of 7.7 parts per billion.10Lake George Park Commission. ProcellaCOR
What the Treatment and the 2025 Study Showed
Early results appeared to favor the agencies. Post-application SCUBA surveys on July 30, 2024, found milfoil in Sheep Meadow Bay effectively eliminated within the treatment zone, with most milfoil in Blairs Bay collapsing, though the northwest edge of that bay showed reduced effectiveness attributed to water currents during application.11Lake George Park Commission. ProcellaCOR Treatment Results Water samples analyzed by the University of Connecticut showed ProcellaCOR dropped below detectable levels in the water column within 24 hours.12Lake George Association. LGA Announces Initial Results of ProcellaCOR Monitoring
The sediment picture was different. On September 25, 2025, researchers from the Lake George Association, Rensselaer Polytechnic Institute, and Paul Smith’s College posted a preprint on bioRxiv reporting that florpyrauxifen-benzyl and its byproducts persisted in Lake George’s bottom sediments for at least one year after application. The study said the herbicide had migrated vertically deeper into the lakebed than earlier research predicted, which the authors suggested explained why the EPA had been unable to establish sediment half-lives in prior lab studies. Measured concentrations in the sediment exceeded the EPA’s 28-day “no observable adverse effect concentration” for chironomids, the small insects that live in lakebed mud. The researchers also documented that lake circulation had spread the herbicide beyond the original treatment boundaries.13bioRxiv. Persistence of Florpyrauxifen-Benzyl in Sediments Following Application to a Large Oligotrophic Lake
The LGA said the findings showed prior regulatory reviews had underestimated sediment persistence, while acknowledging no evidence of risks to drinking water, human health, or recreational use of the lake.14Lake George Association. Lake George Association Releases New Study on Herbicide Persistence in Lake Sediments The Lake George Park Commission’s executive director, Dave Wick, responded that the observed sediment concentrations were “sparse and declining” and did not change the established safety profile. The study was undergoing peer review as of late 2025.15Adirondack Explorer. ProcellaCOR Sediments
Where the Case Stands Now
The broader Warren County suit filed in June 2024 is still pending, and it is unclear whether further court proceedings will follow the release of the sediment study.15Adirondack Explorer. ProcellaCOR Sediments As of 2026, the Lake George Park Commission has said it has no plans to treat milfoil beds in other bays with ProcellaCOR in 2026 and has characterized the 2024 applications as demonstration projects whose data would inform future decisions.16Lake George Mirror. The Knowns and the Unknowns: LGA Releases First Results of Year-Long Study of ProcellaCOR The LGA has called on the commission, the APA, and the DEC to fold the sediment persistence findings into any future management decisions and is examining whether similar persistence has occurred in other Adirondack lakes where ProcellaCOR has been used.