Eurasian Watermilfoil    (Myriophyllum spicatum)

DESCRIPTION

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. Eurasian watermilfoil is a stringy, submerged plant that quickly proliferates in North American water bodies. It is highly invasive and agressively competes with native plant communities reducing biodiversity. Dense mats clog propellers, impair swimming, restrict boating and fishing accesses, and affect water quality. 

 

Identification Eurasian watermilfoil is recognized primarily by its whorls of four feather-like leaves around the stems. Each leaf is finely divided into paired leaflets, typically 12 to 21 pairs per leaf. The number of stems per plant increases as the plant ages. Each individual stem branches several times as it nears the water surface, creating a dense floating mat over the surface of the lake. Dense Eurasian watermilfoil beds usually occur in water between 3 and 20 feet deep. The tops of the milfoil plants, both stems and leaves, often turn red in color.

(Source: 1. Vermont Agency of Natural Resources, Department of Environmental Conservation, http://www.anr.state.vt.us/dec/waterq/ans/ewmcontrol.htm; 2. Minnesota Sea Grant, eurasian watermilfoil: Fact sheet, http://www.seagrant.umn.edu/exotics/eurasian.html; 3. Minnesota Sea Grant, eurasian watermilfoil ID card, http://www.seagrant.umn.edu/exotics/eurasianid.html).

IMPACTS

Eurasian watermilfoil competes aggressively to displace and reduce the diversity of native aquatic plants. It elongates from shoots initiated in the fall, beginning spring growth earlier than other aquatic plants. Tolerant of low water temperatures, it quickly grows to the surface, forming dense canopies that overtop and shade the surrounding vegetation (Madsen et al. 1991, Link). In other words, 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. 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. 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 has less value as a food source for waterfowl than the native plants it replaces (Aiken et al. 1979, Link). And although fish may initially experience a favorable edge effect, the characteristics of Eurasian watermilfoil's overabundant growth negate any short-term benefits it may provide fish in healthy waters. At high densities, its foliage supports a lower abundance and diversity of invertebrates, organisms that serve as fish food (Keast 1984, Link). Dense cover allows high survival rates of young fish, however, larger predator fish lose foraging space and and are less efficient at obtaining their prey (Lillie and Budd 1992; Engel 1995). Madsen et al. (1995, Link) found growth and vigor of a warm-water fishery reduced by dense Eurasian watermilfoil cover. The growth and senescence of thick vegetation degrades water quality and depletes dissolved oxygen levels (Honnell 1992; Engel 1995, Link). Typical dense beds restrict swimming, fishing and boating, clog water intakes and result in decaying mats that foul lakeside beaches.

(credit: Colette Jacono (Author), USGS Nonindigenous Aquatic Species, Eurasian watermilfoil, http://nas.er.usgs.gov/dicots/my_spica.html; 2. Minnesota Sea Grant, eurasian watermilfoil: Fact sheet, http://www.seagrant.umn.edu/exotics/eurasian.html).

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(credit: Colette Jacono (Author), USGS Nonindigenous Aquatic Species, Eurasian watermilfoil, http://nas.er.usgs.gov/dicots/my_spica.html)

As of September 2001 Eurasian watermilfoil has been found in 55 Vermont lakes and ponds.

A variety of physical, chemical, and biological control methods have been used in attempts to manage infestations of Eurasian watermilfoil. Unfortunately, complete eradication is rare. According to Department of Fisheries & Wildlife, University of Minnesota, mechanical or manual, chemical, and biological. Biological controls, with pathogens and insects, are currently being evaluated; operational biological controls are available. Mechanical and manual control, either by hand pulling, raking, or harvesting, is effective at reducing current abundance of plants and is useful to clear channels or maintain access. Water level management and bottom barriers may also be used in some locations. Chemical control can be effective, however, chemical control often needs to be repeated every year to every three years.

YOU CAN HELP

Prevent further spread of Eurasian watermilfoil and other nonnative aquatic species.

Learn to identify Eurasian watermilfoil. Know which lakes are infested.

Get involved! Participate in the Milfoil Watchers Program and help search for Eurasian watermilfoil in one or more of the many still uninfested Vermont lakes.

Contact the Department of Environmental Conservation immediately if you think you have found a new occurrence of Eurasian watermilfoil.

Spread the word, not the plant! Public participation in Eurasian watermilfoil control and prevention is essential to the success of the control program.

Remove all plant material

Discard removed material in a trash receptacle or on high, dry ground where there is no danger of them washing into any water body.

Drain all water boat, boat engine, and other equipment.

Rinse all boat parts with tap water (preferably hot) or leave boat out of water and in sun for at least five days.

Source from 1. Vermont Agency of Natural Resources, Department of Environmental Conservation, http://www.anr.state.vt.us/dec/waterq/ans/ewmcontrol.htm; 2. Department of Fisheries & Wildlife, University of Minnesota, http://www.fw.umn.edu/research/milfoil/milfoilbc/milfoil.html; 3. Aquatic Plant Information System Online Version, http://www.wes.army.mil/el/aqua/apis/methods.html)

Eurasian Watermilfoil: Vermont Department of Environmental Conservation
    http://www.anr.state.vt.us/dec/waterq/ans/ewmpage.htm
This site includes very specific and useful information about eurasian watermilfoil in Vermont: Literature; Spread Prevention and Control; Distribution; and Links.

Purple Pages: Michigan State University
    http://www.msue.msu.edu/seagrant/pp/
This page introduces the Purple Loosestrife Project at Michigan State University. You can learn more about the biological control project, which engages citizens and young adults in the control of purple loosestrife using the plant own natural enemies.

Department of Fisheries & Wildlife: University of University of Minnesota
    http://www.fw.umn.edu/research/milfoil/milfoilbc/milfoil.html
This site provides various control methods for eurasian watermilfoil: Mechanical and manual;  Chemical;  Biological  methods.

Non-Native Invasive Aquatic Plants in the United States: Center for Aquatic and Invasive Plants, University of Florida and Sea Grant 
    http://plants.ifas.ufl.edu/seagrant/myrspi2.html
This site includes well-organized information and pictures about eurasian watermilfoil: Habit;  Habitat;  Identification;  Origin;  Distribution; Control and Literature.   

Eurasian Watermilfoil Factsheet: Minnesota Sea Grant
    http://www.seagrant.umn.edu/exotics/eurasian.html
This sites includes the following information on watermilfoil in Minnesota: their impact, spread methods, control methods, contact information, and useful materials. 

Eurasian Watermilfoil ID Card: Minnesota Sea Grant
    http://www.seagrant.umn.edu/exotics/eurasianid.html
This page provides photographs and information on control and identification of eurasian watermilfoil. 

Grant Lakes Information Network (GLIN): Invasive Species in the Great Lakes Region     
     http://www.great-lakes.net/envt/flora-fauna/invasive/invasive.html
This site includes a comprehensive information on invasive species in the Great Lakes. 
Eurasian Watermilfoil    http://www.great-lakes.net/envt/flora-fauna/invasive/milfoil.html

Aquatic Plant Information System Online Version
    http://www.wes.army.mil/el/aqua/apis/methods.html
This page provides the following information on five aquatic plants (alligatorweed, eurasian watermilfoil, hydrilla, waterhyacinth, and waterlettuce): plant information, control methods, and ecology.