As the 2019 fishing and boating season gets underway, the Minnesota Department of Natural Resources (DNR) is continuing and expanding a multi-faceted approach to combating the spread of starry stonewort, an aquatic invasive species.

The agency is issuing permits for pilot projects, working with local governments and lake associations, and partnering with researchers to limit starry stonewort in Minnesota after it was first confirmed in 2015 in Lake Koronis in Stearns County.

Starry stonewort is an algae that looks similar to other native plants and can form dense mats, which can interfere with use of a lake and compete with native plants. It is most likely spread when fragments have not been properly cleaned from trailered boats, personal watercraft, docks, boat lifts, anchors or other water-related equipment. 

The invasive plant is not in White Bear Lake, nor does Wendy Crowell, DNR aquatic invasive species management consultant, believe it’s inevitable that starry stonewort will reach the lake. 

“There are no lakes in Washington or Ramsey county that are known to have this plant,” she said. “Currently, the species is only known to occur in 13 waterbodies in Minnesota. The treatments of small starry stonewort infestations, particularly near water accesses, help to prevent the spread of the species.  In addition, all of the efforts that people make to clean their equipment, in order to prevent the spread of plants and animals from one waterbody to another, play a very important role in preventing the spread of starry stonewort to new lakes.”


Monitoring and research efforts have led to important new information:

• Starry stonewort may double or triple in size within two to three years in a lake, once it becomes well established.

• Hand removal by divers in small, localized areas appears to be effective, if done carefully. Repeated hand-pulling efforts or follow-up copper treatments may be necessary. Similar to other invasive plants in Minnesota, starry stonewort requires management on an annual basis if suppression is the goal.

• Repeat copper treatments can reduce abundance and slow spread in a given season. Most native plant communities have seen minimal impacts from copper treatments, though a native type of algae that looks similar to starry stonewort, Chara, has been damaged by treatments.


The DNR reminds boaters and anglers to follow Minnesota laws to prevent the spread of aquatic invasive species:

• Clean aquatic plants and animals from watercraft.

• Drain all water by removing drain plugs and keep drain plugs out while transporting watercraft.

• Dispose of unwanted bait in the trash.

   Some invasive species are small and difficult to see at the access. To remove or kill them, take one or more of the following precautions before moving to another waterbody, especially after leaving infested waters:     

• Spray with high-pressure water.

• Rinse with very hot water (120 degrees for at least two minutes or 140 degrees for at least 10 seconds).

• Dry for at least five days.

Details about starry stonewort and other aquatic invasive species are available at


Debra Neutkens 

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