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Extensive search leads to first new confirmation of starry stonewort in a Minnesota lake in 2017

The invasive algae starry stonewort was recently found in Stearns County's Grand Lake. (Minnesota DNR)

Following an organized search of 178 lakes in 20 counties by 200 trained volunteers, the Minnesota DNR has confirmed the invasive algae starry stonewort in Grand Lake in Stearns County.

This is the first new confirmation of starry stonewort in a Minnesota lake in 2017, the DNR said in a news release Tuesday, Aug. 15.

Two other Stearns County lakes were previously confirmed to have starry stonewort: Rice Lake last year and Lake Koronis in 2015. Koronis was the first Minnesota lake where starry stonewort was confirmed.

DNR invasive species specialists confirmed a light, isolated growth of starry stonewort near Grand Lake’s public access. Treatment options are being considered. To date, starry stonewort has not been eradicated from any lake in the United States.

“Although we were hoping to find no new populations, we are glad this one was discovered early, thanks to the people who participated in the coordinated search known as ‘Starry Trek,’ said Heidi Wolf, DNR invasive species unit supervisor. “We’re also encouraged that there hasn’t been a greater number of lakes found to have starry stonewort during this major search.”

“All but one of Minnesota’s nine cases of starry stonewort have been reported in August, when the telltale star-shaped bulbils are most abundant and visible,” Wolf said. “Now is the time for people to look.”

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, the DNR said in the release.

According to the DNR LakeFinder report on Grand Lake, the 650-acre fishery located two miles south of Rockville in eastern Stearns County “has a maximum depth of 34 feet and a modest watershed dominated by row crops, forest and pasture. … Grand Lake is primarily managed for northern pike and walleye and was last surveyed in 2008. Anglers can expect good fishing for smaller northern pike and good-sized walleye.

“Emergent and floating leaf vegetation was common along the south and west shoreline, primarily wild rice, yellow waterlily and bulrush,” the DNR continued in the report. “Submerged vegetation was not surveyed, but coontail and chara were the dominant species in 2008. Curly leaf pondweed was present but rare. Water clarity was good.”

The Aug. 5 “Starry Trek” event was coordinated by the Minnesota Aquatic Invasive Species Research Center, University of Minnesota Extension and the Minnesota DNR. A tandem event, called “AIS Snapshot Day,” involved the River Alliance of Wisconsin, University of Wisconsin Extension and Wisconsin DNR.

This new confirmation is a reminder to boaters and anglers to follow Minnesota laws to prevent the spread of aquatic invasive species, the DNR said in the release. 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.

“We also encourage anyone interested to consider becoming part of an even larger group of trained detectors next year through University of Minnesota Extension,” Wolf said.

Details about starry stonewort and other aquatic invasive species are available at More information about citizen science at the Minnesota Aquatic Invasive Species Research Center and the AIS detector program is available at

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