Invasive Plants in the Watershed

Invasive Hydrilla

In 2009 an invasive aquatic plant called hydrilla was discovered in a small lagoon on the western shore of Damariscotta Lake. Hydrilla is considered to be the worst invasive aquatic plant in North America and is currently found in only one other Maine Lake: Pickerel Pond in Limerick. Damariscotta Lake is the 31st Maine Lake known to host an invasive aquatic plant, and the first known in Lincoln County. A significant Hydrilla infestation would negatively impact recreation, property values and native plants and animals.

It is unknown how this plant was introduced into the lake and how long it has been here. Hydrilla is native to parts of Africa, Australia and Asia. The plant typically occurs in dense, rooted stands but can also be found drifting in mats. It out-competes native plants because it can photosynthesize earlier and later in the day, grows in a variety of conditions, grows fast and spreads easily.

Volunteers Tim and Kate Joy survey the lake for invasive plants.

These volunteers survey sections of the lake’s shoreline once a year looking for invasive aquatic plants. DLWA provides training and equipment, and volunteers complete surveys at their leisure. Survey areas are small and assigned so most volunteers are checking the areas near their homes. Contact Julia for more information or check out the Events Calendar for training dates.

In 2010 more than 175 DLWA volunteers and staff surveyed more than 95 percent of the lake's 45 miles of shoreline. In 2011 DLWA volunteers and staff checked the few places that weren't checking in 2010 and re-checked almost 50 percent of the shoreline and shallow areas. Hydrilla has been found in just one additional location. Since the plant is persistent and spreads so easily, it is important to continue to survey the lake in future years.

Hydrilla Pulling Crew

In September 2011, hydrilla was found in Davis Stream in Jefferson. Davis Stream is one of the major tributaries to Damariscotta Lake, and it is a popular place for boaters, fishermen and wildlife enthusiasts. DLWA and Maine DEP worked together in the fall of 2011 to gauge the extent of the infestation and remove the plants growing there. Though the infestation is not extensive, controlling hydrilla in Davis Stream will require an ongoing effort by DLWA staff and volunteers.

The following resources are available for download to invasive plant patrollers and anyone else interested in protecting their lake from invasive aquatic plants:

• A DLWA brochure: Combating Hydrilla: A Community Effort to Protect Damariscotta Lake
• A presentation on how to identify hydrilla and other invasive aquatic plants
• A presentation on invasive plant survey techniques
• Quick Key to ruling out Maine's 11 most unwanted Invasive Aquatic Plants
• Blank screening survey form
• Instructions for completing screening survey form
• Correctly filled in screening survey form

More information about invasive aquatic plants is available at the Maine Volunteer Lake Monitoring Program's website and the Vital Signs' website.

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