EWM

Milfoil management a top priority on the Eagle River Chain

Eurasian water milfoil (EWM) is native to Eurasia and North Africa, and was accidentally introduced to North America in the1940’s. Eurasian milfoil is one of the worst aquatic plant pests in North America. It is believed to have been introduced to Wisconsin in the 1960’s and is currently known to be present in approximately 600 lakes and rivers.

Eurasian water milfoil is an emergent, herbaceous aquatic plant.  Stems grow to the water surface, usually extending 3 to 10, but as much as 33, feet in length. EWM can form large, floating mats of vegetation on the surface of lakes, rivers, and other water bodies, preventing light penetration for native aquatic plants and impeding water traffic. This was the situation on the Eagle River Chain around 2007 before the milfoil management program began. Eurasian water-milfoil infestations negatively affect birds and fish, and decaying mats of Eurasian water-milfoil reduce oxygen levels in the water.

The stems are reddish-brown to whitish-pink. New plants generate mostly from rhizomes and fragmented stems. It does not spread rapidly into undisturbed areas where native plants are well established. Therefore it is important to promote native aquatic plant growth on the Chain.

Eurasian water milfoil can easily be confused with a number of other plants, including native Northern water-milfoil and native coontail.

Transporting Eurasian water-milfoil fragments on boats, trailers, and in livewells is the main introduction route to new lakes and rivers. So, clean your boat before you leave the ramp!

Click here to visit the DNR website for more information.

In 2008, the Unified Lower Eagle River Chain of Lakes Commission received a WDNR grant to begin management of EWM on the Eagle River Chain using herbicide treatments. The Commission has received grants yearly since then, and the management program continues. Treatment on the Eagle River Chain has been extremely successful in terms of controlling the density and occurrence of EWM. Over the course of annual treatments from 2008 to 2016, EWM acreage has been reduced from 278 acres in 2007 to acres 20 acres in 2016.

At this time, the management strategy has shifted to maintaining the positive strides by balancing a level of EWM tolerance while not allowing the population to return to pre-management levels.

Due to the relatively low population of EWM, no herbicide treatment was conducted in 2016. No herbicide treatment is planned for 2017.

It is never the intent of herbicide treatments to impact native species, and for this reason, native plant surveys were conducted on all lower Chain lakes in 2012.  Results indicated the native aquatic plant community of the lower Eagle River Chain of Lakes is of exceptional quality, and if anything, is of higher quality at present than in 2005/2006 before herbicide treatments began. Native plant surveys will be conducted again in 2017.

Complete information on Chain EWM management can be found on the Commission’s website at http://www.eagleriverchaincommission.org.

You can view the treatment on Cranberry Lake by clicking on the links below.