Management Techniques

Many techniques are available for controlling unwanted aquatic vegetation. Regardless of the method, knowing the potential harmful effects on non-target organisms is important.

Mechanical Control

Mechanical control includes hand-pulling, machine harvesting, hydroraking, benthic barriers and dredging. Typically, these methods are used in localized areas. Dredging requires permits from local, state and federal agencies.

Water Drawdown

Water drawdown, particularly during the winter, when freezing temperatures can damage plants, is a low-cost weed-control option. The Connecticut Department of Energy and Environmental Protection (DEEP) must be notified before any drawdown.

Herbicides

Chemical aquatic weed control involves applying a herbicide to decrease the population of a plant. Invasive plants are rarely eliminated, but the recreational value of a lake or pond can be improved, and the spread of the invasive plant can be slowed. Selecting the proper herbicide and the time of application requires accurate information on the life cycle of the invasive plant. A permit from the state DEEP is required before an aquatic herbicide can be used. Experts at CAES IAPP and the DEEP can answer questions on the use of aquatic herbicides.

Biological Control

Biological control agents, including beneficial insects and microbes, may someday be viable aquatic weed control alternatives. To date, the only biological control used successfully in Connecticut is a plant-eating fish, the grass carp (Ctenopharyngodon idella). This fish is not native and must be certified as sterile (triploid) to assure it will not reproduce in the environment. The DEEP monitors the release of this fish, and a permit is required before they can be purchased. Typically, grass carp are used in small ponds. Containment of grass carp to the body of water where they are introduced is required, and special screens are needed at inflows and outflows.  CAES IAPP started a project in 2006 to assess the distribution and abundance of biological control agents for Myriophyllum spicatum.  (Follow this link for more information on the biological control study.)

Nutrient Reduction

Because plants need nutrients to proliferate, reducing the nutrients reaching the water body may inhibit the growth of invasive aquatic plants. Maintaining unfertilized shoreline buffer zones and minimizing the misapplication of fertilizer to paved areas can reduce the amount of fertilizer that reaches lakes and ponds. CAES offers soil tests that determine fertilizer amounts based on plant needs.