Waterscapes 101

Eurasian Watermilfoil submerged pond weed

Myriophyllum spicatum is a submerged pond weed that is widespread throughout the United States. This is a rooted weed that produces reddish brown stems that grow up to 8 feet long. Feather-like leaves grow in whorls of 3 to 5 around stems.

Another very similar pond weed is parrot feather. While leaves are very similar, parrot feather will emerge up to a foot above the water surface. Attempting to determine pond weed species while it is still in water can lead to misidentification. Coontail and bladderwort are also weeds that look similar while still underwater.

Where does milfoil grow?

Eurasian watermilfoil can grow in 1-15 feet of water. It can grow even deeper in very clear water.

Prolific growth can make this weed very problematic. Once introduced into a body of water, watermilfoil spreads mainly through fragmentation. Broken stems produce new roots. Breakage is often caused by boat motors and wake from boats. Stems can also naturally break off on their own. 

Is watermilfoil an invasive species

Watermilfoil creates a number of issues for both aquatic life and humans. Watermilfoil forms dense mats at the water surface which blocks sunlight from reaching more desired aquatic plants. These weed mats can cause issues for boaters and anglers.

Heavy infestations can even result in decreased dissolved oxygen levels. Aggressive growth can choke out desired native plant species. This is a non-native aquatic plant in the US and also classified as an invasive species.

eurasian water milfoil

Non chemical milfoil removal options:

Raking can be used to remove watermilfoil, BUT it is crucial that all broken stems are removed because of fragmentation.

LakeMats can be installed along docks and shorelines to control milfoil grass in these areas. The mats will need to be maintained, clearing any sediment and debris, so that watermilfoil doesn’t take root.

Grass carp can NOT be used to manage watermilfoil. This is not a desired weed species that they want to eat.

Eurasian Water Milfoil Herbicide Treatment: 

Navigate granular herbicide is an excellent treatment option. This is a systemic herbicide that will provide long term control of milfoil weed. Early season control is ideal.

Sonar provides excellent control with granular and liquid treatment options. This is a long term treatment that kills the roots of pond weeds. This treatment can take 30-60 days for complete control. Because this is a “slow kill”, this provides fish with a safe treatment that does not deplete oxygen levels.

Tsunami DQ is a liquid herbicide that provides good control of watermilfoil. This is a fast acting treatment that produces results within days after treatment. 

Aquathol provides good weed control in both liquid and granular treatments. This treatment carries no water use restrictions.

Watermilfoil Control Treatments