New York State Conservation Council, Inc.

Didymo is an invasive algae that has come to several of New York’s waters.  Nicknamed “rock snot,” it can be distinguished from other algae by its characteristics.  Touching it will feel like wet wool, but not slimy.  Its color is beige/brown/white, but not green.  It securely attaches to stones, and does not fall apart when you rub it between your fingers.

D.E.C. has confirmed finding didymo in the Batten Kill and one tributary in Washington County; also in the West Branch of the Delaware River downstream from the Cannonsville Reservoir, in the East Branch of the Delaware River downstream from the Pepacton Reservoir, and in the mainstem of the Delaware River. The Esopus Creek, downstream of the Shandaken Portal, is infected as well. Didymo grows on the bottom of flowing and still waters and can develop thick mats even in fast flowing trout streams.

While didymo is not considered a significant risk to human health, it creates problems on the bottoms of waterways that it inhabits and is very easily spread from one body of water to another.  It forms thick mats that are barriers to native organisms such as caddis, mayflies and stoneflies, and can potentially smother aquatic plants and destroy fish habitat.  In turn, trout and other fish that feed on those organisms also decline.

The microscopic algae cling unseen to waders, boots, clothing, boats, lures, hooks, sinkers, fishing line, other fishing gear, or any other damp item.  If items are not cleaned and dried completely, the algae can live for months and spread to other bodies of water the next time they are submerged.  Anglers, kayakers, canoeists, boaters and jet skiers can all unknowingly spread didymo by transporting the cells on boats and other gear.  DEC is encouraging anglers to use alternatives to felt-soled waders, such as rubber-studded boots. Felt soles are able to absorb didymo cells and stay damp for long periods of time, and are a major factor in spreading didymo.

DEC is urging anglers and other water recreationists to help prevent the introduction and spread of didymo by doing the following: 
  •  Before leaving a river or stream, remove all obvious clumps of algae and look for hidden clumps. Leave them at the affected site. If you find any later, do not wash them down drains; dispose all material in the trash.
  •  Soak and scrub all items for at least one minute in either hot (140 degrees F) water, a two percent solution of household bleach or a five percent solution of salt, antiseptic hand cleaner or dishwashing detergent. Be sure that the solution completely penetrates thick absorbent items such as felt soled waders and wading boots.
  •  If cleaning is not practical, after the item is completely dry to touch, wait an additional 48 hours before contact or use in any other waterway. Check thick absorbent items closely to assure that they are dry throughout. Equipment and gear can also be placed in a freezer until all moisture is frozen solid.

NOTE: If cleaning, drying or freezing is not practical, restrict equipment to a single water body. While DEC recommends that anglers always take these precautions, it is especially important that any gear used out of state be treated before using in New York waters. 

Currently, no known methods exist for controlling or eradicating didymo once it infests a water body.


UPDATE:  May 12, 2010     
Didymo Found In Kayaderosseras Creek 
DEC announced that didymo (“rock snot”) has been confirmed in the Kayaderosseras Creek in Saratoga County. The Kayaderosseras is a celebrated trout stream, with the downstream sections popular as well for kayaking and canoeing. It flows 35 miles from its source just inside the Adirondack Park to its mouth on the northwest shore of Saratoga Lake.