Eurasian Watermilfoil

[ Myriophyllum spicatum ]

Eurasian Watermilfoil (Myriophyllum spicatum) is an exotic species most likely introduced in the United Sates by the aquarium industry. EWM grows densely and creates a canopy of vegetation that blocks out sunlight suppressing our native plants. EWM can grow to nuisance levels in lake areas previously devoid of such problematic growth compounding its impact.

Eurasian Watermilfoil
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Water Milfoil is a genus of about 45 species of freshwater aquatic plants, with a cosmopolitan distribution. Its name comes from Greek, "myri" meaning "too many to count", and "phyll", meaning "leaf". The leaves above the water are stiffer and smaller than the submerged leaves on the same plant. The flowers are small with four petals and are borne in the leaf axils or in a terminal, emergent spike. It has a long soft but fairly brittle stem. Various Species of Water milfoil have become invasive species in water bodies of nearly every state in the continental U.S. Furthermore, a common species, Eurasian Water Milfoil, is often controlled with pesticides.

Q. What are the best control options?

Herbicide Application:
Herbicide control of EWM is a slam-dunk – EWM is susceptible to a hand full of herbicides. Large-scale treatments must consider many factors, contact us directly when considering whole lake applications. Below are common scenarios that face the typical lakeshore or pond owner.

Which one when?

  1. Big Problem: 
    Navigate herbicide – If EWM is your big problem this is the herbicide of choice. It just plain works and kills the root structure. Note: Navigate will control lily plants. If many weed types are present that require control a broader spectrum herbicide may be a better choice.
  2. Mixed Submerged Weeds:
    Hydrothol 191 granular and Reward liquid or Aquathol Super K Granular are also effective EWM control agents. All three are very broad-spectrum. If you have a mix of submerged weeds these offer a good alternative to Navigate. The term of control may not be as long as Navigate but all offer good relief. 
  3. Whole Pond Treatment:
    Sonar herbicide is another great choice but is not effective in a small control site due to its long contact time requirement. However, for a whole pond treatment it is our #1 choice.

It is hard to recommend cutting or raking when it comes to EWM. The plant easily regrows by fragmentation facilitating its spread. Herbicides work great, reach places that cutters/rakes cannot and last much longer. If the lake already has EWM throughout then physical maintenance in conjunction with herbicide control is helpful.

Q. When is the best time to treat?

Once water temperatures are around sixty degrees or warmer and the plants are viable. Unfortunately, EWM arrives sooner in the spring and stays longer than our native plants thus the control window is longer.

Q. How do I actually apply the product(s)?

Granular herbicides can be spread by a small Hand held spreader or can be tossed by a hand scoop. Liquid herbicides should be applied by a hand held pump up type sprayer or a Solo Back pack sprayer.

Q. How often do I need to treat?

This varies with EWM depending upon adjacent influences and control products. On average, two applications per season. Your treatment site results will establish there own history and hence the future predictability. Keeping good records of your application will expedite any tailoring that need to be done. Remember, we are here help!

Q. How long before I see results?

Generally within ten to sixteen days things will be cleared up.