Eurasian Watermilfoil (Myriophyllum spicatun L.)
Description: Eurasian watermilfoil is a submersed, perennial aquatic plant with leaves arranged in whorls of four around the stem. Each leaf is finely divided into many paired Leaflets, giving the plant a delicate, feathery appearance. The plants are rooted in the bottom and usually branch heavily as they reach the water surface, forming a dense mat. The tops of Eurasian watermilfoil plants frequently have a reddish color. Erect flower spikes rise above the water surface. Flowers are small and are reddish in color. The spread of Eurasian watermilfoil can occur through seeds M most frequently a result of vegetative fragmentation. Eurasian watermilfoil is similar in appearance to several species of native watermilfoils.
Habitat: Eurasian watermilfoil can be found in lakes, ponds, reservoirs, rivers, canals, and drainage ditches. Eurasian watermilfoil grows in shallow shoreline areas as well as in deeper water, 25 feet deep or more. It is tolerant of a wide range of environmental conditions.
Threats: Eurasian watermilfoil is highly invasive and competes aggressively with native aquatic plant species, thereby reducing biodiversity. Dense milfoil infestations can severely impair swimming, boating, and fishing facilities. When the plant grows densely, water quality and fish abundance and distribution can also be affected.
Distribution: Eurasian watermilfoil is native to’ Europe and Asia. It was first introduced into North America in the mid 1940s. The first sighting of the plant was in a pond in Washington, D.C. Since then it has spread to at least 40 states and three Canadian provinces. The quick spread of Eurasian watermilfoil across the country has been attributed mainly to boat traffic, where plant fragments have been transported accidentally from one site to another on motorboat propellers and trailers.
The dumping of aquaria has also been the suspected source of some new Copulations. Eurasian watermilfoil infests 42 lakes and several rivers throughout Vermont, including the Connecticut River.
Control: Eurasian watermilfoil is controlled through various mechanical, chemical, biological, and physical methods. Mechanical methods include harvesting, hydro-raking, diver-operated suction harvesting, and dredging. Some aquatic herbicides, such as fiuridone, triclopyr, and 2,4-D can be effective. Biological methods include the use of the herbivorous Asian fish known as the grass carp (not currently legal in Vermont) and a milfoil-eating weevil (Euhrychiopsis lecontei) native to North America. The use of the weevil is experimental at this time but it has shown some promise. Other techniques used for milfoil control are overwinter drawdowns (lowering lake water levels to expose milfoil to drying and freezing), bottom barriers (mats anchored to the bottom that kill plants by blocking out sunlight), and hand-pulling.
Ayriophyllwn spicatum in North America, Richard Couch and E. Nelson. In: Proceedings of the First International Symposium on Watermilfoil and Related Haloragaceae Species. Vancouver, British Columbia, Canada. July 23-24, 1985.
Aquatic Vascular Plants of New England: Part 6. Trapaceae, Haloragaceae, Hippuridaceac. G.E. Crow and C.B. Hellquist. New Hampshire Agricultural Experiment Station, University of New Hampshire, Durham, New Hampshire. Station Bulletin 524. June, 1983.
For more information about Vermont’s invasive exotic plant species or if you would like to know how you can help. Please contact:
The Nature Conservancy of Vermont, 27 State Street, Montpelier, VT 05602 Tel: 802-229-4425
Vermont Department of Environmental Conservation, 103 S. Main St., Bldg. 10 North, Waterbury, VT 05671-0408 Tel: 802-241-3777
Vermont Department of Fish and Wildlife, 103 S. Main St.. Bldg. 10 South, Waterbury, VT 05671-0501 Tel: 802-241-3715
For additional information about Eurasian Watermilfoil, see Eurasian Watermilfoil.