Watermilfoil, myriophyllum spicatum, is a widespread submerged pond weed throughout the United States. This is a rooted weed that can grow in 1-15 feet of water, even deeper in very clear water. Watermilfoil produces green shoots with feather-like leaves.
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.
Watermilfoil creates a number of issues for both aquatic life and humans. Aggressive growth can choke out desired native plant species. Watermilfoil grows to the water surface in dense mats, which blocks sunlight. These dense mats can cause issues for boaters and anglers. Heavy infestations can even result in decreased dissolved oxygen levels.
Non chemical treatment 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 watermilfoil growth 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.
Watermilfoil treatment options:
Navigate granular herbicide is an excellent treatment option. This is a systemic herbicide that will provide long term control. 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.