The Maine Dept. of Environmental Protection’s Invasive Species Program will have Damariscotta Lake’s .3-acre lagoon between Cranberry Point and Bill Judd’s camp treated with the herbicide fluridone (trade name: Sonar) in order to control the hydrilla infestation found last autumn.
Application will be performed on Fri., June 25, between approximately 1 and 3 p.m.
Hydrilla is an especially aggressive invasive species that is able to displace native plants, fish and other wildlife and degrade water quality.
DEP’s confirmation of this problem plant last September is of great concern because this plant can spread easily and quickly beyond the lagoon, both elsewhere in Damariscotta Lake and into neighboring lakes.
The use of the selective herbicide fluridone is part of a comprehensive strategy to curb the infestation of hydrilla within the lagoon to prevent its spread. Fluridone was chosen for its ability to effectively control hydrilla with the least amount of toxicity to humans, fish and other non-target animal species.
The goal in using herbicide is to reduce the hydrilla infestation in the lagoon by at least 95 percent and halt the plant’s ability to produce new root systems. Both goals will restrict the plant’s ability to spread by way of plant fragmentation, seed production and emergent growth from existing roots.
The herbicide will be applied from a john-boat by Aquatic Control Technology Inc., Sutton, Mass., under contract with Maine DEP. Fluridone affects aquatic plants by being absorbed by their leaves and then disrupting the plant’s ability to convert sunlight into food energy. Because of this mode of action and because this herbicide degrades from sunlight, the contractor will likely apply a booster rate of the herbicide one or more times during the 90 days after initial treatment to maintain its effectiveness during this period.
The DEP will also monitor fluridone concentrations routinely during this time both within the treated lagoon and in the cove adjacent to the lagoon. Because Maine DEP has installed impervious plastic curtains at both outlets of the lagoon, it is expected that the herbicide will be confined to the lagoon only.
Herbicide use is one of several tactics within a long-term strategy to control hydrilla in Damariscotta Lake. Last autumn, Maine DEP staff hand removed several tons of hydrilla in order to reduce overall biomass (plant growth) within the lagoon. DEP SCUBA drivers also hand removed individual plants just outside the lagoon and deployed fabric pond bottom barriers to suppress possible continued growth.
In early 2010, Maine DEP had riprap stone installed across the southern inlet/outlet to prevent potential migration of hydrilla into the rest of Damariscotta Lake. We anticipate installing a riprap barrier across the eastern inlet/outlet next winter.
This autumn, Maine DEP will follow up herbicide treatment by deploying fabric barriers on the bottom of the lagoon that will smother subsequent growth. Throughout this summer and into the fall, Maine DEP SCUBA divers will also routinely monitor the cove adjacent to the lagoon and remove any stray hydrilla plants beyond the lagoon.
For questions about this herbicide treatment, please contact the appropriate individual: DEP Aquatic Invasives Program: Paul Gregory, 441-0627, and email: Paul.Gregory@Maine.gov; Pesticides Toxicology: Lebelle Hicks, Maine Board of Pesticides Control, 287-2731, email: Lebelle.Hicks@Maine.gov; and, Certified Pesticide Application: Gerald N. Smith, Aquatic Control Technology Inc., (508) 865-1000, email: info@aquaticcontroltech.com.
