Ashland County Land & Water Conservation Department
315 Sanborn Ave., Suite 100
Ashland, WI 54806-1014
Scott Caven - Ashland County AIS Coordinator
E-mail: ais.ashlandlwcd@centurytel.net Phone: (715) 682-7187 Fax: (715) 682-0042
June __ , 2012
FOR IMMEDIATE RELEASE
This article was submitted by Scott Caven, Aquatic Invasive Species (AIS) Coordinator for the Ashland County Land and Water Conservation
Department. For more information, please contact him at (715) 682-7187 or ais.ashlandlwcd@centurytel.net.
Alien Invaders: Eurasian Watermilfoil
Of all the aquatic invasive species found in Wisconsin, only a select few have been as detrimental to the environment, economy, aesthetics, human
health, and recreation as Eurasian watermilfoil (Myriophyllum spicatum). Native to Europe, Asia, and northern Africa, Eurasian watermilfoil is the
only exotic milfoil found in Wisconsin (there are seven native milfoil species found in the state). This submersed aquatic plant was accidentally
introduced into the United States in the 1940s and reached Wisconsin’s waters in the 1960s. To date, Eurasian watermilfoil has been confirmed in 45
U.S. states and parts of Canada.
Eurasian watermilfoil has whorls of four feathery leaves, each containing 12 to 21 pairs of delicate leaflets. They have thin, flexible stems that are
often a pinkish-red color. Each individual plant produces four-petaled pink flowers on its spike, a central axis that sticks two to four inches out of the
water. Eurasian watermilfoil can grow to lengths of more than 10 feet, outcompeting native vegetation and creating a monoculture.
Northern watermilfoil (Myriophyllum sibiricum), a native “look-a-like” common in many of Wisconsin’s waters, is often misidentified as Eurasian
watermilfoil. Although the two aquatic plants look very similar, northern watermilfoil only has 4 to 11 pairs of leaflets per leaf; clearly distinguishing
itself from its destructive relative. Coontail (Ceratophyllum demersum), one of the most common native aquatic plants found in Wisconsin’s waters, is
also mistaken for Eurasian watermilfoil; however, coontail does not have individual leaflets.
Eurasian watermilfoil has a huge competitive advantage over the majority of aquatic plants. Although it prefers waters that have high nitrogen and
phosphorus concentrations, warm water temperatures, and highly disturbed lake beds, it can survive in a variety of habitats, depths, temperatures,
levels of sunlight, and nutrient levels. It is especially invasive in highly disturbed environments like boat landings, docks, beaches, and fishing piers, as
well as alkaline waters with high concentrations of dissolved inorganic carbon.
Unlike many aquatic plants, Eurasian watermilfoil doesn’t rely heavily on reproduction by seed. Rather, it reproduces vegetatively by way of
fragmentation, producing and dispersing viable fragments that invade new locations. To complicate matters even further, Eurasian watermilfoil and
northern watermilfoil can hybridize, creating an extremely invasive hybrid. Humans exacerbate the spread by transferring plant fragments on boats,
motors, trailers, equipment, live wells, bilges, and bait buckets; reinforcing the importance of following the aquatic invasive species prevention steps!
Established populations of Eurasian watermilfoil reproduce via shoot fragments and stolons, runners that run along the lake bed. Stolons, stems, and
roots can endure the winter months and store carbohydrates for growth in the early spring. This allows it to start growing long before most aquatic
plants (with the exception on curly-leaf pondweed, another devastating aquatic invasive species, and a few others) and gives it a huge competitive
advantage! But it doesn’t stop there. The plants continue to grow exponentially, blocking out sunlight for native aquatic plants and creating a
monoculture.
Eurasian watermilfoil can have detrimental effects on the environment, economy, aesthetics, human health, and recreation; reduced growth and vigor
of warmwater fisheries, decreased property values for lakehomes on infested waterbodies, floating “milfoil-mats” make the waterbody look “infested”
or “dead,” degraded water quality and increased algae blooms that can threaten human health, and severe drop offs in the quality of boating, fishing,
swimming, and other recreational activities.
If Eurasian watermilfoil does become established in a given waterbody, control efforts – mechanical, chemical, and biological – can be used to prevent
its spread. All of the control efforts have significant upsides and downsides that should be carefully considered before implementing treatment.
Mechanical control is a common method for reducing Eurasian watermilfoil colonies in Wisconsin’s waters. Harvesters cut approximately the top five
feet of the plants, effectively clearing out milfoil from beaches, boat landings, docks, and other high use areas. But this option isn’t species specific,
cutting the desirable native aquatic plants as well. It could also create plant fragments, contributing to Eurasian watermilfoil dispersion. Handpulling is
the preferred mechanical control method for Eurasian watermilfoil. Although highly effective, handpulling is extremely time consuming and is only
logical on relatively small colonies (100 plants or less).
Ashland County Land & Water Conservation - Sound Land and Water Stewardship through Local Leadership
Chemical control is extremely effective at killing off colonies of Eurasian watermilfoil when used properly. Herbicide treatment should be conducted
in spring or early summer when most native aquatic plants are still inactive. This will not only maximize the amount of Eurasian watermilfoil that gets
killed, but increases the likelihood for native aquatic plants to survive and flourish.
Biological control, or the use of an invasive species’ natural enemies to reduce (or hopefully eradicate) its population, has been an effective and publicfriendly approach to reducing populations of Eurasian watermilfoil. Eurhychiopsis lecontei, an herbivorous weevil native to North America, feeds
primarily upon Eurasian watermilfoil and can severely reduce its population in a given waterbody.
Hand-Pulling. Weevils. Harvesters. Drawdowns. Herbicides. Dredging. Bottom-Screening. The list goes on and on. Once established in a given
waterbody, controlling Eurasian watermilfoil can be a nightmare; a frustrating, time-consuming, expensive nightmare.
Controlling established populations of Eurasian watermilfoil is a daunting task and eradication is almost impossible. Like all aquatic invasive species,
the most effective way to control Eurasian watermilfoil is preventing its invasion in the first place. Educating the public to follow all of the aquatic
invasive species prevention steps, protecting and maintaining high aquatic plant biodiversity, and reducing nutrient input (especially nitrogen and
phosphorus) are all required to combat the spread of Eurasian watermilfoil.
Scott Caven, Aquatic Invasive Species Coordinator for the Ashland County Land and Water Conservation Department, has witnessed first hand how
destructive Eurasian watermilfoil can be on a waterbody and everyone that depends on it.
“No matter what you value most about our water resources – recreational opportunities, water to drink, economic value, ecological processes,
aesthetics, or a million other reasons – preventing, containing, and controlling the spread of Eurasian watermilfoil is critical to the sustainability of
enjoying these activities in the future.”
Take these steps to ensure that your actions are not part of the problem, but the solution!

INSPECT your boat, trailer, and equipment.

REMOVE any attached aquatic plants or animals.

DRAIN all water from boats, motors, and equipment.

NEVER MOVE live fish away from a waterbody.

DISPOSE of unwanted bait in the trash.

BUY minnows from a Wisconsin bait dealer.
END