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eurasian watermilfoil: fact sheet

 


 

Eurasian watermilfoil (Myriophyllum spicatum) is an invasive, submersed (underwater) aquatic plant accidentally introduced in the 1940s to North America from Europe, where it is widespread. It most likely reached eastern North America through the aquarium trade, entering the waters when aquarium owners released the contents of their aquariums into local lakes. Eurasian watermilfoil flourished and began to spread westward by clinging to recreational boats. People using Lake Minnetonka near Minneapolis, reported the first Eurasian watermilfoil infestation in Minnesota in 1987. Eurasian watermilfoil now occupies over 120 water bodies throughout the state.

WHY IS EURASIAN WATERMILFOIL A CONCERN?

Eurasian watermilfoil can form thick underwater stands of tangled stems and vast mats of vegetation on the water's surface, especially in shallow, nutrient-rich water. These mats can limit boating, swimming, and fishing. Milfoil generally does not produce mats on the surface in water more than 15 feet deep, and doesn't usually grow in water more than 20 feet deep.

Eurasian watermilfoil can disrupt the ecology of a water body by crowding out important native aquatic plants needed for a healthy fishery. It can potentially reduce property values. Under severe conditions, property owners and lake associations can expect increased costs to keep boat channels open by mechanical harvesting and for costs associated with disposal of rotting vegetation. However, it does not cause problems in every body of water where it is established. In lakes with low water clarity, milfoil does not produce mats in water more than six feet deep, if at all. In parts of lakes where bottom fertility is low, for example in sandy areas, the growth of milfoil and aquatic plants tends to be low.
See
FACTS below for more information.

HOW DOES EURASIAN WATERMILFOIL SPREAD?
Eurasian watermilfoil plants spread naturally through stem fragments and underground runners. Accidental cutting of the plants can start new plants when the fragments are transported by watercraft or on waves and currents to new areas where they can root and grow.


Aquatic weeds (macrophytes) caught on a boat trailer at a Lake St. Clair boat access. Ladd Johnson NOAA/Great Lakes Environmental Research Laboratory

 

HOW CAN YOU HELP PREVENT THE SPREAD OF EURASIAN WATERMILFOIL?
Eurasian watermilfoil may become tangled in boat propellers, transducers, trim tabs, bow lines, fishing nets, and on trailers. Actions you take as a responsible boater are critical in preventing the spread of Eurasian watermilfoil to other Minnesota waters.

    Before leaving a lake or river:
  • INSPECT and REMOVE all aquatic plants and animals
  • DRAIN water from motors, live wells and bait containers
  • DISPOSE of unwanted live bait on land
  • RINSE your boat and equipment with hot (104°F) high pressure tap water or
  • DRY your boat and equipment for at least 5 days


Line drawing of boat from the Minnesota DNR

 

WHAT ARE THE REGULATIONS ABOUT EURASIAN WATERMILFOIL IN MINNESOTA?
It is unlawful in Minnesota to:

  • Transport aquatic plants, including Eurasian watermilfoil or other prohibited species on public roads.
  • Place a boat or trailer with attached aquatic plants or prohibited species into Minnesota waters.
  • Transport water from infested waters.
For more information on Minnesota's prohibited species, look for the "On the Waterfront: The Exotic Species Update" publication on the Minnesota Department of Natural Resource's Web site.

IS EURASIAN WATERMILFOIL IN A LAKE OR RIVER NEAR YOU?
For Minnesota, download the Minnesota Department of Natural Resources' INFESTED WATERS LIST.

BE ON THE LOOKOUT!
Detecting infestations early, when they may be kept at manageable levels, is important. Know where infestations are and learn to recognize Eurasian watermilfoil. Report suspected milfoil infestations in Minnesota to the Minnesota Department of Natural Resources (see contact information below).

WHAT DOES EURASIAN WATERMILFOIL USUALLY LOOK LIKE?

  • Submersed, rooted aquatic plant in shallow waters (less than 30 feet deep)
  • Long branching stems near the surface with soft, feathery leaves
  • Leaves usually attached in whorls of four, but sometimes 3-5
  • Each leaf has 10-21 pairs of leaflets
  • Leaflets are usually closely-spaced
  • Leaves are limp when out of water
  • Top of plants often turn red
  • Small reddish flowers in mid summer
  • Plants can grow up to 15 feet long

DON'T MISTAKE!
Eurasian watermilfoil is only one of six aquatic plants in the watermilfoil family found in Minnesota. It is most commonly mistaken for native Northern watermilfoil which has these characteristics:

  • Leaves attached to stem in groups of 4 (rarely 5)
  • Each leaf has 5-9 pairs of leaflets
  • Leaflets are widely-spaced
  • Leaves are rigid when out of water
  • Plant does not branch at surface

IF YOU THINK YOU HAVE FOUND A NEW INFESTATION OF EURASIAN WATERMILFOIL:
Contact the Minnesota Department of Natural Resources at 651.259.5100 or (888) 646-6367 or mail them a sample of a suspected milfoil plant in a sealed plastic bag.

Mail samples to:

Minnesota-DNR
Eurasian Watermilfoil Program
Ecological Services Section, Box 25
500 Lafayette Rd.
St. Paul, MN 55155-4025

CAN EURASIAN WATERMILFOIL BE ERADICATED FROM A LAKE OR RIVER?
Once Eurasian watermilfoil is established in a lake, it is nearly impossible to eradicate. It does not cause problems in every water body, but for those that it does, three of the most common measures for managing nuisance growth are listed below. Most often, state and federal agencies use more than one of these treatment options to control Eurasian watermilfoil. Increasing public awareness about infestations can help prevent further spread by boaters and anglers to nearby lakes.

CONTROL OF EURASIAN WATERMILFOIL
1. Mechanical Harvesting
2. Biological Control (Univ. of MN Biological Control Research)
3. Chemical Treatment
4. Control Of Eurasian Watermilfoil In Lake Minnetonka

WHAT ARE THE COSTS OF EURASIAN WATERMILFOIL CONTROL?
The Minnesota Department of Natural Resources spent approximately $120,000 for maintenance management of Eurasian watermilfoil in 1999!

FACTS
Impacts of Eurasian watermilfoil based on research:

  • Increased boat repair and maintenance costs (One boat owner in Vermont spent $800 repairing his boat when the motor intake became clogged with milfoil)
  • Declined native plant diversity (Madsen, et, al. 1991; Trebitz 1993)
  • Depressed real estate values (Bates et. al 1985)
  • Inhibited water circulation (Smart and Doyle 1995)
  • Reduced levels of dissolved oxygen, enables nutrients to accumulate…possibly creating unfavorable conditions for macroinvertebrates and fish (Lillie & Budd 1992)
  • Reduced density of invertebrates (fish food) (Keast 1984)
  • Three to four times fewer fish versus native plant beds (Keast 1984)
  • Caused significant increases in permanent pool mosquitoes (Bates et. al 1985)
(Facts compiled and presented by Larry Space and Joanna Wright, "The Impact on Small Lakes of Vermont by the Invasion of Eurasian Watermilfoil: A Property Owner's Perspective.")

NEED MORE INFORMATION?

Lake Minnetonka Conservation District 1999 Eurasian Watermilfoil Final Harvesting Report
(http://www.winternet.com/~lmcd/)

Minnesota Department of Natural Resources 1999 Annual Report of Harmful Exotic Aquatic Plants and Wild Animals in Minnesota
(http://www.dnr.state.mn.us/ecological_services/pubsexotics.html)

Help Managing Eurasian Watermilfoil in Minnesota
(http://www.dnr.state.mn.us/ecological_services/exotics/ewmprog.html)

Nonindigenous Aquatic Species (NAS) Information Resource for the United States Geological Survey
(http://nas.er.usgs.gov/plants/docs/my_spica.html)

Vermont Department of Environmental Conservation
(http://www.anr.state.vt.us/dec/waterq/lakes/htm/ans/lp_ewm.htm)

 

 

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AIS: An Educator's Information and Materials Guide (PDF download)
A Field Guide to Aquatic Exotic Plants and Animals
Eurasian Watermilfoil Factsheet
Eurasian Watermilfoil ID Card
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Exotic Flowering Rush
Exotics To Go! CD
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Purple Loosestrife: What You Should Know, What You Can Do
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Round Gobies Invade North America
Ruffe: A New Threat to our Fisheries
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Sea Lamprey: The Battle Continues
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Three-State Exotic Species Boater Survey
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Zebra Mussel ID Card
Zebra Mussel Overview

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 www.seagrant.umn.edu/exotics/eurasian.html modified January 26, 2010