INVASIVE ALGA DIDYMO IN THE NORTHEASTERN US

The aquatic algae Didymo, also called “rock snot,” has now been confirmed at several sites in New York and Vermont. Unlike many other aquatic invasive plants, didymo (Didymosphenia geminata) grows on the bottom of both flowing and still waters. It is characterized by the development of thick, gooey mat-like growths – which can last for months – even in fast flowing streams. In addition to making footing difficult, didymo can impede fishing by limiting the abundance of bottom dwelling organisms that trout and other species of fish feed on.

There are currently no known methods for controlling or eradicating didymo once it infests a water body.

Didymo mats look like brown or white fiberglass insulation or tissue paper. While didymo appears slimy and stringy, it feels rough and fibrous, similar to wet wool and does not fall apart when handled.

Didymo (called rock snot) is an invasive freshwater diatom (a form of algae), native to Europe. It is attached to the bottom by stalks. As the stalks lengthen, didmyo can form wavy mats. It is distinguished from native algae (usually green in color) by its tan or brown color. Long strands of didymo can often be washed white at the ends. Didymo cells are microscopic, and thus this invasive algae can be spread by a single drop of water.

Anglers, kayakers, canoeists, tubers, boaters and others engaging in water-based recreation can unknowingly spread didymo. The microscopic algae can cling – unseen – to waders, boots, boats, clothing, lures, hooks, fishing line and other equipment and remain viable for several weeks under even in seemingly dry conditions. Absorbent items, such as felt-soled waders and wet suits, require thorough treatment as outlined below.

Water recreationists are urged to use the “Check, Clean and Dry” method to limit the spread of invasive species.

Check - Before leaving a river, stream or pond, remove all obvious traces of algae and look for hidden clumps and leave them at the affected site. If any is found later, it should be disposed of in trash receptacles, not washed down drains.

Clean – Treatment varies. The solution needs to completely penetrate thick, absorbent items such as felt-soled waders and wading boots.

For non-absorbent items, try these methods:
-- Detergent or salt: Soak or spray all surfaces for at least one minute in a 5% solution (by volume) of dishwashing detergent or salt (7 ounces of detergent or salt added to a gallon of water).
-- Bleach: Soak or spray all surfaces for at least one minute in a 2% solution (by volume) of household bleach (3 ounces of bleach per gallon of water).
-- Hot water: Soak for at least one minute in very hot water (140 degrees F – hotter than most tap water) or for at least 20 minutes in water kept at 115 degrees F (uncomfortable to touch).

For absorbent items, longer soaking times are required. Use these methods:
-- Hot water: Soak for at least 40 minutes in water kept above 115 degrees F.
-- Hot water plus detergent: Soak for 30 minutes in hot water kept above 115 degrees F, containing 5% dishwashing detergent.

Dry – If cleaning is not practical, after the item is completely dry to the touch, wait an additional 48 hours before contact or use in any new 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 use to a single water body. DEC encourages anglers to consider alternatives to felt-soled waders such as rubber studded boots.
ALSO, it is especially important that any gear used out of state be treated before use in New York waters.