Starry stonewort confirmed in Wright County’s Pleasant Lake

Two small, dense patches of starry stonewort, 12 to 15 inches tall and covering about 4 square feet, were found in 8 to 10 feet of water, near the county-managed public access on the north side of the lake.

The Minnesota DNR has confirmed the invasive algae starry stonewort in Pleasant Lake, near Annandale in Wright County in central Minnesota, the agency said in a news release Friday, Aug. 10.

This is the second new confirmation of starry stonewort in Minnesota in 2018. A week prior, the DNR confirmed the invasive algae in Medicine Lake, located within the city of Plymouth in Hennepin County, in the Twin Cities metro area. There are now 13 lakes in Minnesota where starry stonewort has been confirmed.

A DNR invasive species specialist confirmed starry stonewort when investigating a report of zebra mussels in Pleasant Lake, which turned out to be negative. Two small, dense patches of starry stonewort, 12 to 15 inches tall and covering about 4 square feet, were found in 8 to 10 feet of water, near the county-managed public access on the north side of the lake.

Staff from the DNR, Wright County and the Pleasant Lake Association are coordinating treatment. Because the patches of starry stonewort are small and deep under the surface, hand-pulling is considered the most effective treatment option in this case.

Following treatment, the access area will be carefully monitored to watch for new growth.  Wright County has closed the public access until further notice. Starry stonewort has never been eradicated from any U.S. lake, but treatment can help reduce the risk of spread and provide nuisance relief for water-related recreational activities.

Since starry stonewort was first confirmed in Minnesota in 2015, most new populations 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. If people think they’ve found starry stonewort, they should report it to the DNR.

Starry stonewort is an alga 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.

Details about starry stonewort and other aquatic invasive species are available at mndnr.gov/ais.

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