Eurasian Watermilfoil

One of the most aggressive and noxious invasive species of aquatic weed found in North American lakes, Eurasian watermilfoil (EWM), has established itself in Lake Leelanau. This determination was confirmed conclusively in 2019 by Brian Price, biologist for the Lake Leelanau Lake Association and former Executive Director of the Leelanau Conservancy, and Jeff Sanborn, past president of the Lake Leelanau Lake Association (LLLA).

Eurasian watermilfoil (Myriophyllum spicatum) is native to Europe, Asia, and North Africa, but has a wide geographic and climatic distribution among some 57 countries, extending from northern Canada to South Africa. Eurasian watermilfoil (EWM) is a rooted, submerged aquatic plant that grows in water from two to 30 feet deep, but most commonly in Lake Leelanau at depths of 8-12 feet. It prefers still or slow-moving water and is considered to be a highly invasive species. Eurasian watermilfoil is known to hybridize with the native northern watermilfoil (M. sibiricum) and the hybrid has also become invasive in North America. This hybridization has been observed across the upper midwestern United States (Indiana, Minnesota, Michigan, Wisconsin) and in the Northwest (Idaho, Washington).

By obstructing water‐based recreation and decreasing a lake’s aesthetic value, infestations of EWM can also lead to a decline in lakefront property value (Eiswerth et al. 2000, Horsch and Lewis 2009, Zhang and Boyle 2010).

EWM was likely first introduced to North America in the 1940s and is now found across most of Northern America, including a number of lakes in Michigan. The plant is now established in Crystal Lake, Duck Lake, Higgins Lake, Houghton Lake, Long Lake, Paradise Lake, Portage Lake, and Walloon Lake, among others. It is recognized as a serious threat by Michigan’s Department of Natural Resources.

Eurasian watermilfoil (EWM) aquatic invasive species beneath Lake Leelanau's surface water.


In lakes or other aquatic areas where native aquatic plants are not well established, the plant can spread quickly. It has been known to crowd out native plants and create dense mats that interfere with recreational activity, including boating, fishing and swimming. Left unchecked, the plant can grow so densely that it can render some lakes virtually unnavigable, seriously affecting property values. By blocking out sunlight to native aquatic plants and preventing them from photosynthesizing, the plant can create zones where the amount of dissolved oxygen is sufficiently depleted that the levels are detrimental or fatal to aerobic organisms. EWM grows primarily from broken-off stems, known as shoot fragments, which increases the rate at which the plant can spread and grow. EWM can also reproduce by producing flowers if it is able to grow up to the surface. Luckily, no flowers have been found in Lake Leelanau due to it being controlled as soon as it was discovered.

Means of Control

When EWM was discovered in Lake Leelanau, LLLA teamed up with the Grand Traverse Band of Ottawa and Chippewa Indians (GTB) to develop a plan. Although biological and chemical control of Eurasian watermilfoil has been employed extensively since roughly 2000, LLLA and GTB decided to tackle this invasive species without the use of chemicals. The partners devised a plan primarily using biodegradable burlap blankets, otherwise known as benthic barriers, to cover the infestations. The barriers do not allow sunlight to reach the plant, eliminating its ability to photosynthesize, and killing the plant below the barrier.

Photo by Joe VanderMeulen
Photo by Joe VanderMeulen

The buoy flags below mark areas where our burlap barriers are placed. Please stay clear of these areas and do not anchor near the buoys, as your anchor could move or tear the burlap and prevent them from killing EWM below.

"Do not anchor invasive species work" LLLA graphic

Action Plan

Since surveying the lake and discovering the extent of the infestation in Lake Leelanau in 2020, LLLA and GTB have spent an enormous amount of time and money actively controlling EWM. Focus has been placed on preventing EWM from spreading into North Lake Leelanau, where it has not yet been discovered, and on tackling the largest infestations that have the highest ability to produce fragments and spread the infestation.

The team of people between LLLA and GTB, which has significantly expanded since work began in 2020, will continue working throughout the summer field season to control Eurasian watermilfoil and keep Lake Leelanau beautiful for all to enjoy.


Reporting Form: Lake Leelanau AIS Prevention

Here comes the big question: What to do if you spot a plant you suspect is an aquatic invasive species? Please report it to us! LLLA has developed an easy-to-use digital form to submit findings if you suspect you have identified an AIS. If it looks like an AIS of concern, one of our biologists will contact you to investigate it further.

Learn More

Each year that the partners have worked to control EWM in Lake Leelanau, a detailed Field Report has been prepared. To learn more about our methods and lessons learned, click below to read the full reports.

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