Starry stonewort confirmed in Pope County’s Lake Minnewaska

The Minnesota Department of Natural Resources has confirmed the invasive algae starry stonewort in Lake Minnewaska in Pope County. This is the second new confirmation of starry stonewort in a Minnesota lake in 2017. 

DNR invasive species specialists confirmed an abundant growth of starry stonewort among native aquatic plants in the narrow Lake Minnewaska marina off the main body of the lake. Additional searches are being conducted to determine whether it is anywhere beyond the marina.

Treatment options are being considered. Starry stonewort has never been eradicated from any U.S. lake, but treatment can help ease lake access and water-based recreational activities.

There are now 11 lakes in Minnesota where starry stonewort has been confirmed. Two were confirmed in 2015, seven in 2016, and two this year. It has been present in at least some of these lakes for several years, rather than being spread to many lakes in a just a year or two.

Since the first case was confirmed in 2015, all but one have been reported in the month of August, when the telltale star-shaped bulbils are most abundant and visible. Now is the best time of year to look for it. Information on how to identify starry stonewort can be found on the DNR’s website, and any suspicious plants should be reported to the DNR.

Starry stonewort is an alga that 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.

This new confirmation 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; and
  • 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 Fahrenheit for at least two minutes or 140 degrees Fahrenheit for at least 10 seconds).
  • Dry for at least five days.

Details about starry stonewort and other aquatic invasive species are available on the aquatic invasive species page.