Starry Stonewort Discovered in Three Waukesha County Lakes


Republished from a Wisconsin DNR news release, Monday, September 9, 2019.


Contact: Amy Kretlow, Southeast Wisconsin AIS Specialist: Amy.Kretlow@wisconsin.gov and (920) 893-8552


Starry stonewort was confirmed in three new Waukesha County lakes – Okauchee Lake, Pewaukee Lake, and Lower Nemahbin Lake – this summer.  One finding was a result of work done by a private lake management company, while the other two findings were found by a citizen as part of a statewide citizen-monitoring event sponsored by the DNR, the University of Wisconsin Extension Lakes, and the River Alliance of Wisconsin.


Starry stonewort is a submerged macro-alga. Though the specific impacts of it are largely unknown, anecdotal evidence suggests that the macro-algae can grow in thick mats at high densities, adversely impacting the fishery and recreational and aesthetic uses. The DNR is working with partners around the country to determine its effects and how best to control it.


"A thoughtful and coordinated approach to managing these new populations will ultimately be most successful in limiting their impacts," said Amy Kretlow, the DNR aquatic invasive species specialist for southeast Wisconsin. "The DNR and invasive species partners will work together with local organizations to manage these findings."


At this time, there are no known effective eradication measures for starry stonewort. Chemical treatment has been attempted but did not effectively reduce the reproductive bulbils that are in the sediment. Mechanical treatments such as hand-removal and diver-assisted suction harvesting (DASH) have seen short-term success followed by regrowth. Wisconsin and other neighboring states are continuing to research control options that can kill or remove the plant while reducing harm to native plant communities.


Starry stonewort is now known to be in 13 waterbodies in Wisconsin and because of its limited distribution, it is still possible to limit its spread throughout Wisconsin. Water users can learn to identify starry stonewort so that it can be reported to the DNR if they come across a new population.


Boaters can help prevent the spread of aquatic invasive species like starry stonewort by performing the following prevention steps:

  • INSPECT your boat, trailer, and equipment.

  • REMOVE any attached aquatic plants or animals (before launching, after loading, and before transporting on a public highway)

  • DRAIN all water from boats, motors and all equipment

  • NEVER MOVE live fish away from a waterbody


The most up to date list of waterbodies with starry stonewort can be found on the DNR website here: https://dnr.wi.gov/lakes/invasives/AISLists.aspx?species=STARRY_STONEW





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