Greater Lake Sylvia Association

Working to maintain and improve Lake Sylvia


What is starry stonewort?

Starry stonewort is similar in appearance to native grass-like algae such as other stonewort's and musk-grass.

Native stonewort 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.

There is an very good video on identifying Starry Stonewort on YouTube.

Starry Stonewort

Starry stonewort pulled from Minnesota's Lake Koronis

If you suspect you have found a new infestation of starry stonewort, or any other invasive species, note the exact location, take a photo or keep the specimen, and contact the DNR.

Why is starry stonewort a problem?

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 than, 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.

How does it spread?

Starry stonewort is believed to be spread from one body of water to another by the unintentional transfer of plant fragments and bulbils, the star-like structures produced by the plant. These fragments, or mud containing them, can be transferred on trailered boats, personal watercraft, docks, boat lifts, anchors or any other water-related equipment that is 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 Clean, Drain, DisposeClean all vegetation, animals, mud and debris from your watercraft and any water-related equipment before you move it from one body of water to another. Drain all water from your watercraft and bait bucket, keep drain plugs out during transport, and Dispose of any unwanted bait in the trash. Clean, Drain, Dispose is required by law in Minnesota.

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.

Starry Stonewort Treatment Plan 

This is a short summary of our conference call with Dr. Rodgers, his graduate student, Steve McComas, and members from the AIS committee: 

Based on their testing of the sediment sample, water sample, and SSw sample, they are recommending the use of liquid Cutrine Plus, an algaecide with an alternative chemical, Clearigate, if Cutrine is not available.

It will be applied using the “trailing hose” method where the chemical is moved down through the water either in a hose or a pipe until it is near the SSw on the lake bottom which should result in almost instant killing.

Steve McComas will have been out diving on the 24th to GPS mark the specific areas where either plants are found or sprouts are emerging from the sediment and will be the basis for where we will be precision treating.  Steve will determine if the SSw is still within the previously discovered areas or if it has spread outside that area, will  look at the density of the plants in a given area, the dispersion of the plants, and from that and in consultation with Dr. Rodgers, we may ask for an amended application permit.

Precision application such as is planned will keep us from having to close the access to boating and prevent us from having to put up a barrier although our intention is to treat very early in the morning before boaters arrive or the wind picks up.  

Treatment will depend on calm wind conditions and a dye will be placed in the water so that McCommas and Dr. Rodgers student, who will be present, can monitor movement of the water and time the chemical will stay in place.

Specifications, including have an ice chest on board the boat doing the application to keep the chemical as dense as possible prior to injecting it into the lake which will increase the concentration level of the chemical on each plant.

Dr. Rodgers suggested the requirements to be used in the request for proposals that have been sent to applicators.  RFPs have already been sent and we are starting to receive responses.  Before any chemicals are applied, the AIS committee will insure that the applicator is meeting all of the requirements as specified by Dr. Rodgers and confirmed by his student at the boat landing site.

After the chemicals have been applied Steve McCommas and Dr. Rodgers student will assess the results of the application of chemical.

Our permit that has been sent to the DNR requests the potential of multiple applications as additional plant material sprouts or starts to grow a week, two weeks, or whatever later time  as determined by divers.  We have been notified by the DNR that all SSw chemical applications now have to be approved by a committee and additional specific information provided. We anticipate application by the middle of June or thereabout.

Starry stonewort are grass-like algae that are not native to North America. The plant was first confirmed in Minnesota in Lake Koronis, near Paynesville in Stearns County, in late August of 2015. Plant fragments were probably brought into the state on a trailered watercraft from infested waters in another state. In August of 2016, starry stonewort was confirmed in several north-central Minnesota lakes in Beltrami, Itasca and Cass counties. DNR invasive species staff found that a number of other reports of suspected infestations were native species that appear similar to starry stonewort.   

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