Starry stonewort is a grass-like form of algae that are not native to North America. The plant was first confirmed in Minnesota in Lake Koronis in late August of 2015. Plant fragments were probably brought into the state on a trailered watercraft from infested waters in another state.
Starry stonewort is similar in appearance to native grass-like algae such as other stoneworts and musk-grass. Native stoneworts and musk-grass are both commonly found in Minnesota waters. Starry stonewort can be distinguished from other grass-like algae by the presence of star-shaped bulbils.
Starry stonewort can interfere with recreational and other uses of lakes where it can produce dense mats at the water's surface. These mats are similar to, but can be more extensive then, those produced by native vegetation. Dense starry stonewort mats may displace native aquatic plants.
Like all plants, starry stonewort may grow differently in different lakes, depending on many factors. At this time, we cannot predict how it might grow in any one Minnesota lake.
Means of spread
Starry stonewort is believed to be spread from one body of water to another by the unintentional transfer of bulbils, the star-like structures produced by the plant. These fragments are most likely attached to trailered boats, personal watercraft, docks, boat lifts, anchors or any other water-related equipment that was not properly cleaned.
What can people do to prevent its spread?
The most important action you can take to limit the spread of starry stonewort and other non-native aquatic plants is to remove all vegetation and animals from your watercraft and any water-related equipment before you move it from one body of water to another. Make sure you drain all water from your watercraft and bait bucket and dispose of any unwanted bait in the trash.
What can be done to reduce starry stonewort?
The potential to manage the plant is not well documented. It appears that treatment with herbicides can suppress starry stonewort. Some states use hand pulling, which may be a way to reduce biomass in small areas. Mechanical removal can also be effective. In the case of a newly discovered population of starry stonewort that has a limited distribution in the lake, mechanical harvesting is not recommended because it might create fragments that would speed the spread of the invasive plant within the lake.
(Information provided by the Minnesota Department of Natural Resources)