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SLELO PRISM

Eurasian Watermilfoil

Eurasian watermilfoil (Myriophyllum spicatum L. ) 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 is not a valuable habitat for larger fish species. 

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.

Leaves:  Submerged, feathery, limb when out of water, 4 – 5 leaves whorl around the stem at each node.  Typically uniform in diameter, consists of 9 – 21 thread like pairs of leaflets that resemble bones on a fish spine.
Flowers:  Tiny, inconspicuous, and located in the axils of flower bracts, either four petals or without.  Flower spike rises 2 – 4” above the water surface.
Fruit:  Four jointed nut-like bodies.
Stem:  Slender, thickened below the flower, doubles in width further down, becomes leafless near the base. Usually 3 -10’ long but can reach 33’ in length.  Often branch repeatedly at the waters surface.
Reproduction:  Primarily by fragmentation due to boating and wave action.  Fragments stay alive for weeks if kept moist.  They also reproduce by runners.
Control:  Hand-pulling is the best method.  Raking is also an option. All plant fragments must be removed from the water and shoreline.  Manipulating the water level may help if that is possible to do.  2,4-D and Fluridone are the most commonly used chemicals used against this species.  However, both of these have mixed results and can affect native plant populations.  Researchers have found a native North American weevil that feeds on Eurasian Water-milfoil, but this method also has mixed results.

Identification

Leaves:  submerged, feathery, limp when out of the water, 4 – 5 leaves whorl around the stem at each node.  Typically uniform in diameter consists of more than 12 thread-like pairs of leaflets that resemble bones on a fish spine.

                                                                                    ewmf-leaves

Flowers:  tiny, inconspicuous, and located in the axils of flower bracts, either four petals or without.  Flower spike rises 2 – 4” above the water surface.

                                                         water-milfoil-flower

Fruit: 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 divides into 4 chunky 3-sided seeds.

      ewmf-seeds

Stem:  slender, thickened below the flower, doubles in width further down the stem, becomes leafless near the base. Usually, 3 -10’ long but can reach 33’ in length.  Often branch repeatedly at the water’s surface.

 ewmf-stem

Reproduction:  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, Dry all watercraft before entering and leaving a body of water.

ZTZ2006_inside2

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:

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.

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Select another species

Black & Pale Swallow-worts |   Giant Hogweed |  Purple Loosestrife |  Water Chestnut | Glossy Buckthorn |  Eurasian Water Milfoil |  Rock Snot, DidymoEuropean FrogbitJapanese Knotweed

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PREVENTION
Prevent the introduction of invasive species into the SLELO PRISM.

EARLY DETECTION & RAPID RESPONSE
Rapidly detect new and recent invaders and eliminate all individuals within a specific area.

COOPERATION
Share resources, including funding personnel, equipment, information, and expertise.

INFORMATION MANAGEMENT
Collect, utilize, and share information regarding surveys, infestations, control methods, monitoring, and research.

CONTROL
Control invasive species infestations by using best management practices, methods and techniques to include: ERADICATION (which is to eliminate all individuals and the seed bank from an area), CONTAINMENT (which is reducing the spread of established infestations from entering an uninfested area) and SUPPRESSION which is to reduce the density but not necessarily the total infested area.

RESTORATION
Develop and implement effective restoration methods for areas that have been degraded by invasive species and where suppression or control has taken place.

EDUCATION & OUTREACH
Increase public awareness and understanding of invasive species.

INNOVATION
Develop and implement innovative technologies that help us to better understand, visualize, alleviate or manage invasive species and their impacts or that serve to strengthen ecosystem function and/or processes.

Rob Williams
PRISM Coordinator

Megan Pistolese
Outreach and Education

Brittney Rogers
Aquatic Invasive Species

Robert Smith
Terrestrial Invasive Species

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