Eurasian Watermilfoil

Eurasian Watermilfoil at a Glance

The Plant:

A perennial plant that grows in fresh or brackish water, (Myriophyllum spicatum). Generally grows 3’--7’ tall but can grow to 20’. May hybridize with native milfoils.

The Problem:

Invasive! Grows to a lake’s surface, creating large surface mats that limit light penetration necessary for native species. Mats can impede navigation and recreational activities and dense colonies may impede the movement of fish.

How It Spreads:

Primarily through vegetative fragmentation—fragments break off, settle in sediment, grow roots, and establish new plants.

First Discovered:

2023. By a Volunteer Monitor!

Where Identified (2023):

Confirmed plants or colonies have been found in Manitowish Lake and n the channel between Alder Lake and Manitowish Lake.

Need for Volunteer Monitors:

Yes! North Lakeland Discovery Center staff and Onterra LLC cannot be all places at all times.  Efforts to control Eurasian Watermilfoil and to keep it from spreading throughout the Chain and down the Manitowish River will require knowing where it is.  Volunteer monitoring is essential.

Eurasian Water Milfoil, Trout River ( Channel Between Alder & Manitowish Lakes), August 2023
Eurasian Water Milfoil Trout River 2023

Eurasian Watermilfoil in Manitowish Waters

Eurasian Watermilfoil discovered. Eurasian Watermilfoil was found on July 15th 2023 by an AIS volunteer. Eurasian Watermilfoil had not previously been identified in Manitowish Waters’ lakes or rivers. Suspected floating fragments were found in Alder Lake and rooted plants in the channel between Alder and Manitowish Lake.

Follow-up Surveys: Follow up surveys were conducted by Vilas County Land and Water Conservation Department and North Lakeland Discovery Center staff including visual inspection, snorkeling and rake throws. No further floating or rooted samples were found in Alder Lake, but three medium colonies and 27 other locations of rooted plants were found in the channel between the Alder and Manitowish Lakes, as well as at four sites in Manitowish Lake during additional surveying. Removal could not be attempted in the fall of 2023 due to the plants being brittle, a seasonal occurrence.

The Path Forward: A Rapid Response Grant has been applied for and awarded to the North Lakeland Discovery Center with the MWLA providing the cost share for the grant. In 2024, monitoring will resume and the removal process will begin. Removal through pulling and anticipated diver assisted suction harvesting (D.A.S.H.) will be done by Discovery Center staff and Aquatic Plant Management LLC, an environmental services provider.

For further information on Eurasian Watermilfoil monitoring, check out the Events page or contact the Discovery Center at [email protected]

It is critically important that control efforts are supplemented through monitoring of our waters to ensure that appropriate steps are taken to limit or prevent the spread of Eurasian Watermilfoil. 

Join the effort.

Eurasian Watermilfoil Video

Paul Skawinski, from the UW Extension Lakes program, talks about Eurasian watermilfoil in Wisconsin.