Starry stonewort confirmed in just 17th Minnesota lake

Starry stonewort forms dense surface mats in lakes.

The Minnesota DNR has confirmed the invasive algae starry stonewort in Pimushe Lake, about 20 miles northeast of Bemidji in Beltrami County.

Beltrami County Environmental Services contacted the DNR after finding starry stonewort during an early access detection check. The DNR is conducting searches to determine the locations and extent of starry stonewort in the lake.

The DNR will work with Beltrami County and the Beltrami County Lakes and Rivers Association to consider management options. Funds are available for an immediate response that could include hand pulling, herbicide applications and other methods as appropriate.

Starry stonewort has never been eradicated from any U.S. lake, but treatment or careful removal can help reduce the risk of spread and provide nuisance relief for water-related recreational activities. Early detection is key to effective management.

With the addition of Pimushe Lake, starry stonewort has now been confirmed in 17 of Minnesota’s 11,842 lakes. It was first confirmed in Minnesota in 2015.

Pimushe Lake is in close proximity to other Beltrami County lakes with confirmed populations of starry stonewort, but Pimushe is not directly connected to any of those lakes.

As summer progresses, starry stonewort’s small white star-shaped bulbils become more visible, making it easier to distinguish from other aquatic plants. Information on how to identify starry stonewort can be found on the DNR’s website. People who think they’ve found starry stonewort or any other invasive species new to a lake should report it to the DNR by contacting their area invasive species specialist.

About 200 Minnesota lakes are searched annually for starry stonewort during the “Starry Trek” event coordinated by University of Minnesota Extension, scheduled for August 21 this year. In each of the past three years, one Minnesota lake has been newly confirmed with starry stonewort following the “Starry Trek” searches.

Starry stonewort is an alga that looks similar to native aquatic 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 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.

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