Group of eelgrass underwater.

Control Eelgrass

Many people ask how to get rid of eelgrass, also called Vallisneria. The following options can be considered for how to control Vallisneria eelgrass.

Click here to read more about identifying this plant.

 

Manual/Mechanical Control:

If you are considering how to remove eelgrass, physically raking this plant and digging up the roots can be a somewhat effective method of control. While physically removing Eelgrass  can be difficult. It is the most sure vallisneria control method. Eelgrass can re-grow from any roots or fragments remaining in the water.

 

Herbicide Control:

There are multiple options for how to kill eelgrass that offer some control. Mostly these herbicides can brown and damage the vallisneria, but may not result in full control. Combining the application of Aquathol K and Semera or Flumigard, Mizzen or Copper, and/or Diquat can provide higher impact on vallisneria or eelgrass control.

  1. Aquathol K/Super K (for ponds or lakes) – liquid that is diluted with water and sprayed or granules that are broadcast over the plants.
  2. Semera or Flumigard (for ponds or lakes) – granules that are dissolved and mixed or liquids that are mixed and diluted with water and sprayed over the plants (early morning is best), fast-acting
  3. Dibrox (for ponds or lakes) – liquid that is diluted with water and sprayed over the plants, fast acting.
  4. Hydrothol (for lakes) – granules that are broadcast over the plants.

 

Algaecide Control:

Copper algaecides, including Mizzen, have been shown to kill eelgrass plant cells. While generally unable to provide complete control, copper algaecides can be used to boost the effectiveness of the herbicides above in vallisneria control. They also help provide control of algae that will grow in and on the eelgrass plants.

  1. Mizzen [Copper Algaecide] (for ponds or lakes) – liquid that is diluted with water and sprayed. Works together with herbide
  2. Copper sulfate *Max label rate* (for ponds or lakes) – granules that are broadcast in the target area.

 

When treating eelgrass,

  • Treat when the plants are established and actively growing.
  • Dibrox or Hydrothol will give some control of eelgrass. It is very difficult to get rid of completely.
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