Didymo Discovered in Lower Yough
Inside the Outdoors, June 15
, 2012

Fishermen and boaters beware. Didymo, also known as rock snot, was confirmed as of last week to be present in the Lower Youghioheny River, so stated Stacie Hall, assistant manager of the Department of Conservation and Natural Resources at Ohiopyle State Park.

It is a microscopic alga known as a diatom that’s invading our rivers and streams. Didymosphenia geminata can smother entire stream beds with mats as thick as eight inches and can ruin just about any river or creek.

According to the Pennsylvania Fish and Boat Commission website, “Didymo can be found on rocks in moving water and is often mistaken for fiberglass or toilet tissue. Unlike most other algae, didymo feels like wet cotton and isn’t slimy. It is generally brown, tan or yellow in color.”

It spreads from place to place via fishing equipment, waders, boats and anything that comes in contact with it. To put a stop to those entering on or in waters known to carry this algae, all boats, trailers, boots and other gear must be disinfected before moving to a new stream.

Before leaving at body of water, always check all items and floatation devices to make sure algae is not clinging to surfaces. If by chance it is found at a later time, treat and discard. “Do not wash down drains,” the PFBC said.

There are various methods one can use to kill this algae. Following are some of the Commission’s suggestions:

  • Detergent – soak or spray all surface for at least one minute in 5% dishwashing detergent or (2 cups (16 oz,) or 500mls with water added to make 2.5 gallons or 10 litres);
  • Bleach – soak or spray all surfaces for at least one minute in 2% household bleach (1cup (8 oz.) or 200 mls with water added to make 3 gal. or 10 litres);
  • Hot water – soak for at least one minute in very hot water kept above 140 Fahrenheit (60 degrees Centigrade) (hotter than most tap water) or for at least 20 minutes in hot water kept above 113 Fahrenheit ( 45 degrees Centigrade) (uncomfortable to touch).

Some items need a longer soaking saturation time. For example, felt-soled waders require 40 minutes of soaking in hot water kept above 113 degrees Fahrenheit or hot water plus detergent calls for 30 minutes in hot water kept at 113 degrees or 45 Centigrade containing 5% dishwashing detergent. Freezing any item until solid will also kill didymo.

Once the items are dry, that also will kill this algae. Keep in mind, slightly moist didymo can survive for months. The Commission states, “To ensure didymo cells are dead by drying, the item must be completely dry to the touch, inside and out, then left dry for at least another 48 hours before use. If cleaning or drying is not practical, restrict equipment to a single waterway.”

Here again, check the item as to thickness. “The denser the material,” the PFBC said,
“the better it will be at holding moisture. (and live cells), the slower it will be to dry out and the more difficult it will be to soak completely with cleaning solutions.”

Here again, additional recommendations were made so as to not spread this infestation.

  • Soak porous materials for longer than the specified times to ensure saturation with cleaning solution;
  • Choose a decontamination solution that will not adversely affect your equipment;
  • Follow manufacturer’s safety instructions when using products;
  • Dispose of cleaning waste well away from waterways.

There is a little more work when it comes to boats. Inspect every inch of your boat, trailer, and equipment – the hull, drive unit, trim plates, props, anchor, centerboards, paddles, wheels, hitch chassis, etc. – and remove aquatic plants, animals, and mud from the boat, trailer and equipment before leaving the area.

We who have had boats know the importance of draining the boat before heading home. This is no different. Do the same, making sure all water is on land and not any in the boat or on equipment.

Do not dump leftover bait in the water. When it comes to crawlers, kill them. Invasive earthworms may be packed with Canadians. If so, when they are discarded on land, they will eat the roots of hardwood trees.

Disinfect live wells and bait wells, bilges, cooling systems, hulls, and decks with a 1:9 solution of household bleach and water allowing at least 10 minutes contact time. Rinse well to remove all residual chlorine.

Rinse your boat with hot water. If it is not available, then let it sit for five days to become completely dry before entering a new water body.

The Commission advised boat owners not to transport live fish, other critters, plants or water from one body of water to another.

Hall said, “We want to contain this infestation as much as possible. We will be putting together educational materials as well as surveying our waterways within Ohiopyle to get a better idea of the problem.”


- Paul J. Volkmann
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