SLELO PRISM

Invasive watermilfoil (Myriophyllum spicatum L. ), commonly called Eurasian watermilfoil, is a submerged aquatic plant native to Eurasia and northern Africa.  It has the ability to overwinter and grow rapidly in the spring, blocking out sunlight needed by native plants. It impairs the ability of some fish to spawn and reduces the health of aquatic habitats.

Habitat

Occupies water 3 – 12’ deep, growing best in fertile, fine texture, inorganic sediments.  Prefers highly disturbed lake beds, heavily used lakes and lakes receiving nitrogen- and phosphorus-laden runoff.  Also found in ponds, slow-moving streams, reservoirs, and estuaries.   It is not successful in undisturbed areas where native plants are well established.

Identification

Leaves are submerged, feathery, with a blunt tip, and go limp when taken out of the water. There are four to five leaves that whorl around the stem, each leaf has 12-21 thread-like pairs of leaflets.

Flowers are small red, pink, or yellow, 4-parted flowers on a spike that projects 2-4 inches above the water surface

Fruit are globoid-ovoid in shape measuring 2 mm. Long with 4 lateral lobes; these lobes are smooth, except along their margins, where they may be slightly warty. Each fruit is divided into 4 chunky 3-sided seeds.

Stems are long, slender, branching, hairless, and become leafless toward the base. They can grow up to 2t feet in length. Stems are generally limp when out of the water and often appear reddish, particularly near the plant tips.

Reproduction: Eurasian watermilfoil spreads primarily by fragmentation due to boating and wave action.  Fragments stay alive for weeks if kept moist.  They also reproduce by runners. Therefore, it is important to Clean, Drain, and Dry all watercraft before entering and leaving a body of water.

Control/Management

Physical Control: Hand-pulling is the best method for small infestations.  Raking is also an option. All plant fragments must be removed from the water and shoreline to prevent spreading the infestation. Bottom barrios (sheets of materials, attached to a lake bottom) can be used locally around docks by preventing plant growth by blocking sunlight.

Chemical Control:  2,4-D and Fluridone are the most commonly used chemicals to control this species.  However, both of these have mixed results and can affect native plant populations. Permits are required for chemical applications in aquatic and sensitive habitats; always follow chemical instructions. 

Biological control: Researchers have found a native North American weevil that feeds on Eurasian water-milfoil, but this method also has mixed results. Contact local DEC for more information. 

For more information:

• New York Invasive Species Information

Photo Credits: Title photo, Huron Watershed Counsel, http://www.hrwc.org/category/invasive-species/page/2/.Leaves photo: Lake George Association, http://www.lakegeorgeassociation.org/what-we-do/Invasive-Species/Eurasian-Watermilfoil.asp. Flower photo: Sydney Weed Committee,http://sydneyweeds.org.au/weed/eurasian-water-milfoil/./Fruit photo:USDA,http://plants.usda.gov/java/largeImage?imageID=mysp2_004_ahp.tif. Stem photo: Early Detection & Distribution Center, http://www.eddmaps.org/ontario/distribution/point.cfm?id=3908281.