Eurasian watermilfoil

Descriptionmilfoil_07

Eurasian watermilfoil (Myriophyllum spicatum) is an “exotic” aquatic plant. Exotic meaning that it is not native to this area, but it is native to Europe, Asia and Northern Africa. Eurasian watermilfoil has slender stems whorled by submersed feathery leaves and tiny flowers produced above the water surface. The flowers are located in the axils of the floral bracts, and are either four-petaled or without petals. The leaves are threadlike, typically uniform in diameter, and aggregated into a submersed terminal spike. The stem thickens below the inflorescence and doubles its width further down, often curving to lie parallel with the water surface. The fruits are four-jointed nut-like bodies. Without flowers or fruits, Eurasian watermilfoil is nearly impossible to distinguish from Northern watermilfoil. Eurasian watermilfoil has 9-21 pairs of leaflets per leaf, while Northern milfoil typically has 7-11 pairs of leaflets. Coontail [which is native and prevalent in Liberty Lake] is often mistaken for the milfoils, but does not have individual leaflets (Wisconsin Department of Natural Resources, 1999).

Problems

Eurasian watermilfoil reproduces by fragmentation, thus it does not rely on seed for reproduction. This reproduction allows for the plant fragments to be dispersed and carried by water currents and wind or inadvertently picked up by boaters. Milfoil reproduces extremely rapidly and can infest an entire lake within two years of introduction to the system (Washington State Department of Ecology, 2002). Milfoil is most commonly transported via boats, motors, trailers, bilges, live wells, or bait buckets, and if moist can stay alive for weeks.

Eurasian milfoil is very invasive and can provide only a single habitat by replacing the native plant species and in turn threatening the integrity of aquatic communities. It also inhibits the aesthetic and recreational uses like swimming, boating, and fishing. Severely infested waters display a dense yellow-green matt of vegetation and give off the appearance that the water is “infested” or “dead.” The decomposition of the plant mass at the end of the season results in nitrogen and phosphorus loading, and the cycling of nutrients from sediments to the water column by Eurasian watermilfoil may lead to deteriorating water quality and algae blooms of infested lakes (Wisconsin Department of Natural Resources, 1999).

Eurasian watermilfoil was believed to have been introduced to the eastern United States around the 1940s, but it is possible that it may have arrived as early as the late 1800s. The first known herbarium milfoil specimen in Washington was collected from Lake Meridian near Seattle in 1965 (Washington State Department of Ecology, 2002).

Distribution

Eurasian watermilfoil has been spreading throughout Liberty Lakes’ perimeter since it was first discovered in 1995. Removal was controlled by divers until 1997, when the infestation became to great to handle, then Aqua-Kleen® Granular 2,4-D became the primary treatment. Each spring, aquatic weed diving surveys are conducted by Clearwater Scuba, L.L.C. and the LLSWD to evaluate potential growth and effective treatment. 2,4-D treatments have occurred since 1998 in northern and southern sections of the lake where the infestation remains in the shallow shoreline areas of approximately 1 to 3 meters in depth.

It is of concern of the district and the community that if the density of the milfoil increases that it could potentially crowd out native vegetation and impede human recreation and aquatic habitat. Another very important concern of the district and the community is the potential for the spread of Eurasian watermilfoil to other lakes in the surrounding area. There are other waterbodies in the area that currently are not infested with Eurasian watermilfoil, and it is our concern to reduce the chances of infestation, or reduce the further spread of milfoil to other lakes or waterbodies. Liberty Lake is a popular recreational lake for the greater community and residents, unified with its history; the community has a strong affinity to protect it. Thus in response to the numerous concerns, the Liberty Lake Sewer and Water District wants to evaluate all control options and means of management for the invasive weed for suppression and future control of milfoil within Liberty Lake.

Management

The Liberty Lake Sewer and Water District has taken the community concerns acutely and researched the means of management for the invasive weed. In October of 2002, the Liberty Lake Sewer and Water District was awarded a grant by the Washington State Department of Ecology (DOE) to develop an Integrated Aquatic Weed Management Plan for Liberty Lake. The report is the result of collaboration and research for a probable solution to the Eurasian watermilfoil infestation at Liberty Lake. As part of the plan’s development, the Liberty Lake Sewer and Water District encouraged representation from the community, neighboring lake communities, aquatic consultants, Washington State Department of Ecology, Washington State Department of Natural Resources, and the Washington Department of Fish and Wildlife. A special thanks to the Washington State Department of Ecology and Kathy Hamel for their time and funding to make this project possible.

More recently, the Liberty Lake Sewer and Water District received grant funding for the Liberty Lake Milfoil Management Implementation Project from Washington Department of Ecology’s Aquatic Weed Management Fund. Up to $100,000 was offered to the Liberty Lake Sewer and Water District to cover 75 percent of the eligible project costs for the Liberty Lake Milfoil Management Implementation Project for five years (2004-2009). The project funded was implementation of the Aquatic Weed Management Plan that was drafted and funded in October 2003. It is the intent of the Liberty Lake Milfoil Management Implementation Project to implement the management strategy outlined in the plan. The full text of the Liberty Lake Integrated Aquatic Weed Management Plan is available below. For more information, please contact Jeremy Jenkins at (509) 922-5443 ext. 230.

Liberty Lake Integrated Aquatic Weed Management Plan (17.02MB)
Updated February 24, 2004

also on the DOE website at:

http://www.ecy.wa.gov/programs/wq/plants/planning.html

Public education is an important element in the control of aquatic nuisance plants. Signs have been developed by DOE to bring attention to the Eurasian watermilfoil infestation in lakes and to show fishermen and other lake users how to avoid transporting aquatic plants from one lake to another. These signs have been installed at the public boat launch at Liberty Lake. Educational flyers are available at the District’s administrative building and have been distributed to residents and concerned citizens. Mailings and newspaper articles are also written to inform residents of the infestation and best management practices that can be applied to limit the spread and future degree of infestation.

The Sewer and Water District recognizes that the effective management will be an on-going concern and will require a long-term commitment. The Liberty Lake Sewer and Water District is willing to fund the follow-up activities necessary to ensure continued milfoil eradication and management. Monitoring of the plant community and beneficial uses such as fishing, boating, and swimming needs to be continued.

Other Information

For more information about Eurasian watermilfoil (Myriophyllum spicatum), please check out the links listed below.

http://www.ecy.wa.gov/programs/wq/plants/weeds/milfoil.html

http://www.ecy.wa.gov/programs/wq/plants/plantid2/index.html

http://www.ecy.wa.gov/programs/wq/plants/grants/fy2004.html

http://www.ecy.wa.gov/programs/wq/pesticides/final_pesticide_permits/noxious/noxious_index.html