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Starry Stonewort

NYS counties in which starry stonewort has been identified
NYS counties in which starry stonewort has been identified

Starry stonewort is an invasive algae with a plantlike structure that is native to Eurasia. 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. Stonewort is associated with several negative social and economic impacts throughout the Great Lakes.

Where is starry stonewort located?

Starry stonewort has been reported in fourteen counties in New York State: Cayuga, Chautauqua, Cortland, Franklin, Jefferson, Lewis, Monroe, Onondaga, Ontario, Oswego, Otsego, St. Lawrence, Tompkins, and Wayne. Unfortunately, starry stonewort is difficult to distinguish from closely related muskgrasses and stoneworts so there may be places where it has not yet been detected.

How do I identify starry stonewort?

Starry Stonewort has branches growing around main stems
Starry Stonewort branches grow around main stems

Starry stonewort has 4-6 long branches growing around each stem and can grow more than 7 ft. (2 m) tall in water more than 30 ft. (10 m) deep. It forms dense mats of vegetation that look like pillows (with plants of different heights) along the bottoms of ponds and lakes with still, alkaline water and forms star-like reproductive structures. It is tolerant of both salt and freshwater and tends to grow on sand and gravel in both shady and sunny areas.

How does it spread?

Starry stonewort is named for its star-shaped reproductive structures, or bulbils, which can be transported in mud. Starry stonewort can also spread by fragments and is often found near docks and marinas indicating that watercraft likely transport this algae from site to site.

Tiny star-shaped bulbils among the branches and stems of starry stonewort star-shaped reproductive structure

Why is it a problem?

We are still in the process of studying and understanding the impacts of starry stonewort, but initial reports indicate that it has the potential to negatively impact native species including outcompeting native plants that provide food and shelter for native invertebrates and fish. Its dense mats of vegetation may also negatively impact native fish spawning and phytoplankton (small native aquatic plants that are eaten by fish and invertebrates).

Dense mass of starry stonewort vegetation along a lake bottom

What are the tools for management?

Both chemical (herbicide) and manual (hand-pulling and harvesting) controls have been used with varying success. Research is currently being conducted throughout the Great Lakes Region for best management practices. Preventing the spread of this invasive is critical.

What can I do to help?

  • Clean, drain, and dry your watercraft, trailer, and equipment before and after each use - Regulation 6 NYCRR Part 576 requires everyone who uses watercraft on public waters to follow these practices.
  • When possible, use the following methods to fully decontaminate your equipment.
    • Clean the outside of the watercraft and trailer with high pressure (2500 psi) hot water (140 degrees F) for 10 seconds.
    • Flush the inside of the motor and all compartments (bilge, live well, bait buckets, ballast, etc.) with hot water (140degrees F) for two minutes.
    • Soak fishing gear and equipment in hot water (140 degrees F) for two minutes.
  • Dump bait bucket water where it came from or on land.
  • Consult the DEC website more information on cleaning your boat.
  • If you think you've found starry stonewort please take several photos and submit a report to iMapInvasives (leaves DEC website).