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Special Newsletter Starry Stonewort (SSW)

Updated: Sep 21, 2022


The last aquatic plant survey was done in August 2020. In July 2022, the LDLD Board of Commissioners(BOC) discussed and approved a proposal for an Aquatic Plant Survey to be performed in August of this year by Brian Suffern of Marine Biochemists.

On August 23, Brian Suffern notified the LDLD BOC of a “potential” finding of Starry Stonewort(SSW) on the southeast shore of Lake Denoon. Brian contacted the WI DNR.

On August 29, the potential finding of SSW was shared at the annual membership meeting.

On September 2, the WI DNR was on the lake and found a few more SSW plants in the same area as Brian’s finding. Plant samples have been taken by the WI DNR for further analysis and confirmation.

On September 8, the finding of SSW was confirmed by Patrick Siwula, WI DNR Southeast Region AIS Coordinator.

What is SSW and Why do we care?

Starry Stonewort is an invasive, non-native, aquatic algae belonging to the order Charales (includes all Chara and Stonewort species). It is identified by its “whorls” (arrangement of leaves that radiate from a single point and surround or wrap around the stem or stalk) of 4-6 branchlets (leaves) with blunt tips, irregular length branchlets are arranged along the main thallus (stem). SSW reproduces via fragments or vegetative structures called "bulbils" which is the main identifying characteristic

SSW forms dense mats of vegetation that can reduce the diversity of native aquatic plants in a lake. It can also impede movement of fish and other animals, and may impact spawning activity of some fishes. Mats growing to the surface can reduce water flow and make recreational activities difficult. It can grow in water depths up to 9 meters or 30 feet.

SSW was found only in only one relatively small area in the lake (out of 460 areas sampled). It is reasonable to assume that our SSW patch is small and young. However, the WDRN noticed that the collected specimen contains many bulbils which indicates that the plants have been around long enough to create ‘seeds’ in preparation for reproduction next season. However, in our favor, the area in which SSW was found is crowded with other native species. The WDNR has seen SSW patches not expanding due to resource competition with other plants.

How did SSW get here?

It was likely introduced to the Great Lakes from ballast water and has spread to inland lakes in New York. It was first discovered in the United States in the St. Lawrence Seaway in 1978. SSW has spread primarily to states surrounding the Great Lakes including NY, MI, IN, WI, and MN. The first discovery in WI was in Little Muskego Lake in 2014.

Most likely, SSW “hitched a ride” on a trailer, boat, PWC or barge that had been in an infected lake, such as Little Muskego, Big Muskego or Wind Lake, and was NOT properly “decontaminated” prior to launching on Lake Denoon. SSW was found in front of a few houses east of the Hart Drive boat launch.

Requirements for Vendors Hired to Install/Remove Piers and Boat Lifts

When hiring a business or person(s) to install/remove your pier or boat lift, be sure to ask how they comply with the WI DNR decontamination and disinfection regulations prior to making any commitments or signing a contract.

The DNR Manual Code #9183.1 outlines the minimum decontamination and disinfection steps to be taken every time a barge, boat, gear or equipment is moved between any bodies of water or wetland to prevent the spread of aquatic invasive species.

Decontamination steps include inspection and manual removal of plants, animals and mud. Drain all water from boats, motors, live wells, bilge and transom wells as well as equipment, gear and vehicles. Disposal of plants and animals appropriately to prevent transport to other bodies of water or rerelease where they came from.

Disinfection must follow decontamination and be effective for known invasive species. One of the following must be used:

  1. Store dry for 5 consecutive days after cleaning with soap and water and/or high pressure water

  2. Wash with 212 F (steam) or >140 F water

  3. Apply a 500 ppm Chlorine solution for 10 minute contact time

  4. Apply a 2:100 solution of Virkon Aquatic for 20 minutes contact time

What can we do to manage and control SSW?

Manual removal of starry stonewort is difficult, but can be an option for small populations. Diver-assisted suction harvesting (DASH) has been used to increase the efficiency of manually removing starry stonewort. Care must be taken to remove the bulbils as well, or these bulbils will sprout new plants.

Some chemical herbicides have been able to reduce starry stonewort, but effectiveness tends to decrease as the strands get taller and more dense. An effective biological control agent is not known at this time.

Next Steps

The LDLD BOC and the WDNR have developed a preliminary action plan to monitor growth of our SSW patch several times next year. Details are yet to be worked out but the WDNR may be able to assist with monitoring. The LDLD BOC will also begin to prepare an application for a ‘AIS Rapid Response’ grant which will help with costs in the event that Diver Assisted Suction Harvesting or other actions are deemed appropriate. The WDNR warns against over aggressive treatment at this stage as we can easily make the situation worse by over-clearing plants in the affected area and thereby making more real estate for SSW to grow.

We will publish updates on this situation as they emerge.

Additional Resources:

You can find out more about Starry Stonewort on the WDNR Starry Stonewort website page.

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