Residents: Starry stonewort a 'lake killer' for Minnesota lakes

- Starry stonewort. It has a strange name, but a potentially devastating impact on lakes. While the macro algae has only been spotted on two Minnesota lakes, some Minnesotans are already calling the invasive species a “lake killer.” And they want to warn the rest of the state to “worry.”

The weed — stringy and dense — was first found on Lake Koronis, near Paynesville, about a year ago. Since then, it has spread to much of the lake.

Mike Mackedanz, who has lived on the lake for 41 years, told Fox 9 the weed looks like “raw sewage” and he fears the day when it will make recreation on the lake almost impossible.

The invasive algae is very dense, so swimming through it is dangerous and it can entangle motors.
“It will take over a lake area,” Kevin Farnum, a member of the Koronis Lake Association board, told Fox 9. “It’s important for everyone to realize this is kind of a state issue, and that we need to be very aggressive on this.”

Fighting the invasive is difficult: it is dense so chemicals do not always reach enough of the macro algae, and each cell is an individual that must be individually killed. The lake association started a pilot project to fight the invasive algae: removing weeds before adding chemicals — hoping that thinning the weeds will allow chemicals to better penetrate them.

Meanwhile, the Minnesota Department of Natural Resources offers the same recommendations for reducing the spread of invasive species in Minnesota lakes.

How to prevent the spread of invasive species in Minnesota lakes

  • 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

More information can be found here.

In addition to Lake Koronis, starry stonewort has also been found on the connected Mud Lake and, most recently, on Turtle Lake near Bemidji. 


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