Here is the DEP letter informing property owners of the treatment
July 31, 2025
Dear Lake Arrowhead Shorefront Owner:
A contractor for the Maine Department of Environmental Protection (DEP) will apply herbicide in portions of Lake Arrowhead to control the invasive aquatic plant brittle naiad (scientific name Najas minor). A map showing treatment areas will be posted here: https://www.maine.gov/dep/water/invasives/.
The herbicide treatment is scheduled for Thursday, August 7, 2025. If the treatment is postponed, notification will be posted at the same website noted above. The herbicide application contractor Solitude Lake Management will arrive the morning of August 7th. The treatment will take most of the day.
The aquatic herbicide AquaStrike (Active Ingredients: Dipotassium salt of endothall and Diquat dibromide) will be applied via subsurface injection through perforated hose from an airboat into the treatment areas. Maine DEP will collect water samples from the treatment area for endothall and dibromide analysis by A&L Laboratory.
The treatment goals are to reduce occurrences of brittle naiad to 1) limit spread within Lake Arrowhead and to other waters and 2) enable future control of this infestation with non-chemical measures.
The following restrictions on the AquaStrike label (http://www.cdms.net/ldat/ldBRQ006.pdf) apply to the treatment areas:
- drinking water restriction for 3 days post application
- livestock/domestic animal consumption restriction for 1day post application
- irrigation to turf and landscape ornamentals restriction for 3 days post application
- irrigation to food crops and production ornamentals restriction for 5 days post application
Please do not swim or boat in the area where the airboat is operating during the treatment. While there is no swimming restriction for AquaStrike, we ask you to refrain from swimming in the event of a spill or other accidental release of herbicide. Keeping your boat ashore avoids collisions that invite such accidents.
Questions can be directed to Maine DEP: John McPhedran, john.mcphedran@maine.gov (207) 215-963 or Toni Pied, toni.pied@maine.gov (207) 955-0810.