Skip to main content

Why Herbicides are Needed on Chautauqua Lake

Economic Impact of Chautauqua Lake

66% of visitors to Chautauqua County utilize a lake or a waterway

47% of sales tax of the county is generated in the municipalities immediately surrounding Chautauqua Lake

$282 million dollars is spent annually by tourists in the county, with associated state and local taxes generating $36 million dollars for our communities

Chautauqua Lakefront properties pay 25% + of County property tax 

Invasive Species are a problem that requires sustained local actions to control

  • Excessive growth of invasive species in Chautauqua Lake occurs (without herbicide treatments)
  • Native plants do NOT typical reach the surface, form canopies, or reach the density of these invasives (curly leaf pondweed and eurasian water milfoil)
  • Dense stands of invasives 
    • Crowd out and displace native species
    • Inhibit water movement and warmer water temperatures (both conditions that promote HABs)
    • Can lead to fish mortality
    • Eventually decay and lead to muck build-up on the lake bottom
    • Interfere with all types of recreational use


Herbicides need to be considered when the problem can’t be managed by other means

Benthic Barriers – These are similar to landscape fabric placed on the lake bottom; they are not selective (kill everything underneath) and not practical for large areas 

Biological/Milfoil weevils – No proven successes, stocking company went out of business 

Hand-pulling & DASH (Diver assisted suction harvesting) – Not efficient or cost effective for large areas

Mechanical Harvesting – CLA capacity is limited

  • 2.5 acres/day x 6 harvesters x 5 days = 75 acres/week
  • Cut milfoil typically re-grows to the surface within 6 weeks 
  • 6 weeks x 75 acres = 450 acres (Best Case Scenario)
  • The CLA operational season is typically 12-13 weeks, so only 450 acres can be cut 2x over the entire season, then will continue growing into the fall
  • For context, the Chautauqua Lake littoral zone is about 4000 acres, and has had up to an estimated 2345 acres of milfoil infestation (2021)

Herbicides used in Chautauqua Lake since 2020

Aquathol K for Curly Leaf Pondweed    Endothall Fact Sheet_FINAL

  • Applied (not Sprayed) into the lake 
  • Controls Curlyleaf pondweed at an application rate that is lower than what affects other plants 
  • No fishing or irrigation restrictions 
  • Studies show no impact to largemouth bass spawning 
  • Swimming restricted until the day after application (only in New York) 
  • Temporary drinking water restriction (more than 4.5 miles from CI intake)

ProcellaCOR EC for Eurasian Water Milfoil (EWM)    procellacor-fact-sheet-wisconsin-dnr

  • Applied (not Sprayed) into the lake 
  • Systemic – Kills entire plant including roots & impact persists for 3 years!
  • Selective – Minimal to no impact on native plants 
  • No restrictions on drinking water, swimming or fishing 
  • 1ppb limit on irrigation & livestock watering (to prevent having to evaluate the unanticipated impact of livestock manure on terrestrial plants)
  • Extremely low application rates (2-6ppb) 
  • Concentrations unmeasurable (<1ppb) within 3-4 days

Herbicide treatments have contributed to a healthier, more enjoyable Chautauqua Lake


Response to CLA Statements regarding herbicide use in Chautauqua Lake:    Solitude-Chautauqua-CLA-response-022321.docx

Lake George controversy:  The Lake George Commission vs. Lake George Association

Vermont Federation of Lakes: Assessment of control options for Eurasian WatermilfoilJust another weed?

New York DEC:  Invasive Species Tiers,  DEC video The Univited (fast forward to minute 38), Diet for a Small Lake