Lake St. Catherine Poultney will be treated with a chemical to control the invasive plant Eurasian milfoil.
The herbicide is expected to be applied today to dense beds around the lakeshore.
The public is advised not to swim, boat or fish in the lake, or Lily Pond, Little Lake and the outlet stream to North Road until Wednesday, the third day after the treatment.
The state also advises against using the water for drinking, or for food and drink preparation until further notice.
Officials say the use of the herbicide is part of a lake-wide plan, which includes manual and mechanical methods to control milfoil.
