Invasive Plant Species

The Diamond Lake AIS Monitoring System. In an effort to prevent the spread of HWM and EMF into Diamond Lake, we have installed an invasive species monitoring system at the boat launch on the south end of the lake. A sensor detects the presence of a vehicle either launching or retrieving a boat. The motion triggers a recording that warns users about the dangers of hitchiking vegetation and requests that they check boats and trailers and dispose of any plants well away from the lake. A camera also records all of the activity during the launch or retrieval and retains the images for review by our AIS monitors. Bayfeld County has a strong invasive species transport ordinance and violations can (and have) been prosecuted.

Eurasian water milfoil (EWM) (Myriophyllum spicatumis) is a devastating aquatic invasive plant of the highest concern in Bayfield County. Rising from the bed, it grows across the surface causing thick and dense mats of vegetation that can get tangled in boat propellers and block sunlight from native plants below. It is carried from lake to lake on boats and in bait buckets, live wells and ballast water. Eurasian water milfoil can spread quickly and efficiently, primarily because of its ability to produce adventitious roots after fragmenting. A single strand, even after being cut into tiny fragments by a boat propellor, can produce many sprouts, each becoming a new plant.

A hybridized species between EWM and the native Northern milfoil (Myriophyllum exalbescens) is also invasive in our lakes. In many ways HWM is of even greater concern because it appears to be more resistant to herbicide treatment and its growing habits seem to have a competitive advantage over both its parents.

Hybrid Eurasian water milfoil (HWM) is now spreading throughout nearby Lake Namakagon (link here) and is a threat to Diamond Lake and other neighboring water bodies because of possible contamination via boats that visit both lakes.

Hybrid and Northern Milfoil Compared cro

The two strands at the left are hybrid milfoil in comparison to native northern milfoil (redish stem). The image on the right is a closer view of HWM. The native species generally has fewer leaflets (the needles) per leaf, typically 6 to 26. Eurasian and hybrid species typically have more, 24-36 and 16-28 respectivly.  Images by Jenifer Parsons Washington State University Department of Ecology.

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The Wisconsin Department of Natural Resources maintains an informative website on Eurasian water milfoil and describes how to identify EWM and distinguish it from native species. Bayfield County also maintains an AIS website with more information.