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Forest Service asks for public help in stopping the spread of invasive Didymo algae to protect rivers and streams

Contact(s): Carol Underhill, Public Affairs Officer, (530) 226-2494

Redding, Calif. – Fishermen and other Trinity River users are being asked to clean their clothing and gear to help stop the spread of Didymo a.k.a. “Rock Snot”, which is a type of invasive algae produces thick mats that cover stream beds, making swimming, fishing and other water activities undesirable.

“People, including fishermen, are thought to be the main way that Didymo is being spread from one place to another,” explained botanist Lusetta Sims. “Recreational equipment, including clothing, can become contaminated and encourage the spread of Didymo if not cleaned properly before being used in another body of water.”

Didymo (Didymosphenia geminate) has a slimy appearance and attaches to submerged plants, rocks, and other hard substrates in rivers and streams by excreting a stalk that is resistant to degradation by bacteria and fungi. It has been documented in several locations along the Trinity River from Trinity Dam to Helena. Land managers are concerned that Didymo could become established in other Forest Service tributaries, potentially altering the natural ecosystem.

“Didymo has extraordinary capacity to negatively impact river and stream ecosystems,” said Sims. “It is invasive and prevention is all we have to protect uncontaminated water bodies, creeks and tributaries.”

If you think you have seen a Didymo bloom, Sims ask that you please write a brief description of what you saw and where. If possible, take GPS coordinates as well. Drop off your information at a Weaverville Ranger located at 360 Main Street Weaverville, CA 96093.

Sims explained these steps river users can take to stop the spread of Didymo:

  1. INSPECT clothing, shoes, waders, and all gear.
    1. Remove all mud and debris that has been in the water.
  2. At home, CLEAN gear with hot water and ONE of the following:
    1. Dish soap: 1 cup per gallon water
    2. Bleach: 1/2 cup per gallon water
    3. Table salt: 1 cup per 1.25 gallons water
  3. SCRUB non-absorbent items thoroughly with one of the solutions.
  4. SOAK clothes, waders, and absorbent items in HOT soapy or salty water for 30 minutes, then rinse.
  5. DRY completely for at least 48 hours or FREEZE gear until frozen solid and completely dry.


The mission of the U.S. Forest Service, part of the U.S. Department of Agriculture, is to sustain the health, diversity and productivity of the nation's forests and grasslands to meet the needs of present and future generations. The agency manages 193 million acres of public land, provides assistance to state and private landowners, and maintains the largest forestry research organization in the world. Public lands the Forest Service manages contribute more than $13 billion to the economy each year through visitor spending alone. Those same lands provide 20 percent of the nation's clean water supply, a value estimated at $7.2 billion per year. The agency has either a direct or indirect role in stewardship of about 80 percent of the 850 million forested acres within the U.S., of which 100 million acres are urban forests where most Americans live.

To view a .pdf version of the news release, click here.