On Wednesday the firm SOLitude Lake Management began treating DEC-designated areas of the lake with the chemicals Aquathol K and Navigate, which are intended to kill lake vegetation.
The firm is hired by Chautauqua Lake Partnership along with the participating municipalities, including the villages of Celoron and Lakewood and the towns of Ellicott, North Harmony and Ellery.
About 400 acres is being treated. The application of the chemicals began Wednesday morning and will continue through the day Friday, weather permitting.
The CLP has said that herbicide treatments are meant as a last resort to manage invasive weed species Eurasian milfoil and curly-leaf pondweed.
Despite concerns from some county residents and other lake groups regarding the negative health and environmental impact the herbicides may have on people, wildlife and the environment, the state DEC moved forward at the start of this month to grant permission for the herbicides to be used.
Residents are advised not to swim during the treatments and 24 hours after they finish. In addition, Lake water should not be used for irrigation until 21 days after treatment is completed.