Stop didymo!

Didymo is a concern for our trout streams because it can destoy stream habitat. New Zealand has experienced serious impacts to habitat, fishing, and aesthetics. As you may have heard, didymo is now here in New York State along with our neighbors in Vermont and Connecticut.

Didymo is a single-celled micro-organism that can live for days on waders if moist, and as it is soft and cottony, can stay moist for a while. This stuff is very nasty and easily spread. It can be spread from one river or lake to another by the movement of water, equipment, clothing and any other damp item.

People and their activities, including fishing, are the main cause of spreading. To ensure you don't spread didymo or other aquatic pests, wherever possible restrict equipment, boats, clothing and other items for exclusive use in a single waterway. 

If you are moving items between waterways, you must Check, Clean, Dry.

CHECK: Before you leave a river or lake, check items and leave debris at site. If you find any later, treat and put in rubbish. Do not wash down drains.

CLEAN: There are several ways to kill didymo. Choose the most practical treatment for your situation which will not adversely affect your gear.

* Non-absorbent items:

  • Detergent: soak or spray all surfaces for at least one minute in 5% dishwashing detergent or nappy cleaner (two large cups or 500 mls with water added to make 10 litres); OR
  • Bleach: soak or spray all surfaces for at least one minute in 2% household bleach (one small cup or 200 mls with water added to make 10 litres); OR
  • Hot water: soak for at least one minute in very hot water kept above 60 °C (hotter than most tap water) or for at least 20 minutes in hot water kept above 45 °C (uncomfortable to touch).

* Absorbent items require longer soaking times to allow thorough saturation. For example, felt-soled waders require:

  • Hot water: soak for at least 40 minutes in hot water kept above 45 °C; OR
  • Hot water plus detergent: soak for 30 minutes in hot water kept above 45 °C containing 5% dishwashing detergent or nappy cleaner; OR
  • Freezing any item until solid will also kill didymo.

DRY: Drying will kill didymo, but slightly moist didymo can survive for months. 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.

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