Eurasian Water Milfoil

Scientific name: Myriophyllum spicatum L.

Eurasian Water MilfoilEurasian Water Milfoil is an "exotic" aquatic plant. Exotic means that it isn't native to Minnesota -- it is native to Europe, Asia and Northern Africa. Aquatic means that it lives in the water. Eurasian Water Milfoil was brought to North America in the 1940s.

Eurasian Water Milfoil likes to live in lakes, ponds, shallow water reservoirs and slow moving rivers and streams. It reproduces very fast and in many different ways. If a stem breaks off, it can start a new plant. It also produces flowers and seeds that appear above the water, while the rest of the plant is under water. And it spreads by roots or runners (stolons) in the ground. It is also very tolerant of cold water, so it can grow fast in cold Minnesota lakes in early spring.

Eurasian Water Milfoil grows and spreads really fast. So fast, that it can choke out native plants and reduce the amount of light that reaches into the lake. This aggressive growth kills off other native aquatic plants. And when the native plants can't grow, other aquatic species that rely on the native plants for food and shelter have trouble surviving. Eurasian Water Milfoil's dense growth makes it difficult for invertebrates and other organisms that fish eat to survive. So, with less to eat and less open water, fish populations also decrease.

Have you ever tried to swim in weeds? Kinda' hard, isn't it. Well, imagine a whole lake full of Eurasian Water Milfoil -- so full that it's almost impossible to swim in, fish in, or drive a boat through. If you were a fish it would be really hard to live in a lake so full of milfoil that you couldn't swim around and catch food.

Eurasian Water Milfoil on a LakeThis is a picture of Eurasian Water Milfoil on the surface of Lake of the Isles in Minneapolis, Minnesota during the summer of 1991. You can see that most of the lake was covered with Eurasian Water Milfoil.

What does it look like?

Eurasian Milfoil looks almost like Northern Milfoil, which is native to Minnesota. But, Eurasian Milfoil has 12 to 21 leaflet pairs, while Northern Milfoil has only 5 to 10 leaflet pairs. But, the best way to tell the two apart is to pick them up. Eurasian Milfoil is limp and soft, while Northern Milfoil (the native species) is stiff and bristly.

What do I do if I find Eurasian Water Milfoil in my lake?

Eurasian Water Milfoil - UnderwaterPeople can do a lot to stop the spread of Eurasian Water Milfoil. If you find some, call the Minnesota Department of Natural Resources at 651-297-8021 or 1-888-MINNDNR.

To prevent introducing Eurasian Water Milfoil into other lakes, be sure to do the following:

  • Remove all plant materials from your boat, anchor, trailer and anything that entered the water after you take the boat out of the water and before you leave the boat access area.
  • Drain livewells and bilge water before you leave the boat access area.
  • Make sure your bait bucket doesn't have any plant material in or on it. Be sure to empty your bait bucket on land -- never dump live fish from a bait bucket into a body of water.
  • Wash down your boat, trailer and tackle with hot water when you get home to kill off any hitchhikers that could be transported into other lakes.

So, what are scientists doing to stop Eurasian Water Milfoil?

Glad you asked. Scientists and researchers in Minnesota are trying all kinds of different ways to stop the spread of Eurasian Water Milfoil. Here are some of the things they're working on.

  1. Biological Control. Biological control means using natural methods to control a pest. This includes natural predators or disease organisms that eat or infect the pest to kill it or slow its growth. The most effective control method so far is to use the Milfoil Weevil. This weevil is native to North America and normally feeds on our native Milfoil. However, if given the choice, it prefers to feed on Eurasian Water Milfoil. these little weevils lay their eggs in the stems of the milfoil and when the larvae hatch, they eat the milfoil and cause lots of damage. Here's what the weevils look like:


    Weevil  Weevil


  2. Chemical Control. Chemical herbicides can be applied to Eurasian Water Milfoil every one to three years to control its growth. But since Eurasian Water Milfoil is similar to our native milfoil, the herbicides can often kill the good, native plants that we don't want to hurt. This method is also expensive and can cost from $200 to 2,000 per acre.


  3. Mechanical Control. This is where the Eurasian Water Milfoil is pulled out or cut with a machine and removed from the water. But, since this stuff grows so fast, it usually comes right back. Cutting and removing the milfoil will open up an area for a little while, at least. This type of control must be repeated all summer and it can cost from $300 to 600 per acre.

Coloring page

Milfoil Weevil
Milfoil Weevil
gif or PDF icon Eurasian Water Milfoil


Credits: The photos on this page are courtesy of the University of Minnesota Department of Fisheries, Wildlife & Conservation Biology and are used with their permission.