Didymo

Didymosphenia geminata

Didymo

Didymo

Legal Status: Unwanted Organism - MPI
Status in New Zealand: Investigating
Organism: Marine and freshwater plants

Pest and disease search

Didymo, hornwort, lagarosiphon and other freshwater pest plants are spread by a range of human activities. If you are moving between waterways, you must Check, Clean, Dry.

Information for Sporting Event Organisers

Interactive PDF resource Link to PDF document (2667 KB) to help event organisers encourage participants to Check, Clean, Dry.

Video

  • Check, Clean, Dry DVD
    A guide to clean water related equipment to help slow the spread of freshwater pests

Information for trampers Link to PDF document (393 KB)

Freshwater pest brochures

Cleaning methods

Cleaning methods for specific activities

  

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 500mls 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 200mls 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.

When cleaning equipment, we recommend that you:

  • soak porous materials for longer than the specified decontamination times to ensure cleaning solution has soaked right through the item before soaking for the required decontamination time
  • 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

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.

NOTE: The thicker and denser the material, 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.

Cleaning factsheets