The ORC’s Environmental Data Portal is experiencing high traffic volumes affecting its effectiveness at present. The site is being worked on at present and people are asked to be patient. Please be considerate in using this tool, some people require access to the EDP for important decision-making today.
Environmental Data PortalThe ORC’s Environmental Data Portal is experiencing high traffic volumes affecting its effectiveness at present. The site is being worked on at present and people are asked to be patient. Please be considerate in using this tool, some people require access to the EDP for important decision-making today.
Common name: | Didymo |
Scientific name: | Didymosphenia geminata |
Management programme: | Unwanted organism |
Didymo - also known as 'rock snot' - is a type of algae. It can form massive blooms on the bottom of streams, rivers and lakes, and its spread is highly undesirable.
Didymo impacts on water quality, biodiversity and economic and social values.
This microscopic pest can be spread by a single drop of water. Even if you can't see it, you could be spreading it.
The algae is native to northern Europe and North America, and was first reported in New Zealand in 2004. Since then, Didymo has been confirmed in various lakes and rivers across Otago, however, are many waterways in New Zealand that still require safeguarding. The Ministry for Primary Industries has declared the South Island a Controlled Area for Didymo. This makes it a legal requirement to clean all gear used in the water before going from one waterway to another.
Didymo is not yet present in the North Island of New Zealand.
To prevent the spread of freshwater pests, including didymo, whenever you move between waterways you must check, clean and dry any equipment that comes into contact with water.
Before you leave any river or lake:
Check - remove any plant matter from your gear and clothing and leave it at the site. Don’t wash plant material down the drain.
Clean - soak or scrub all items using one of the below treatments:
Cleaning option | Amount | Duration |
---|---|---|
Dishwashing detergent or nappy cleaner | 10% mix (1 litre to 10 litres of water) | Soak or spray all surfaces and leave wet for at least 10 minutes |
Bleach | 2% mix (200mls to 10 litres of water) | Soak or spray all surfaces for at least 1 minute |
Hot water above 60°C |
Soak entire item
|
Soak for at least 1 minute
|
Hot water above 45°C |
Soak entire item |
Soak for at least 20 minutes |
Freezing | Until solid |
Note: 60° C is hotter than most tap water; 45°C is uncomfortable to touch. Allow longer times for absorbent items.
Dry - ensure your gear is completely dry to touch, inside and out, then leave to dry for at least another 48 hours before you use it. Didymo can survive for months on moist gear.
If it’s wet, it’s a threat.
Remember to check, clean and dry all equipment, before you leave any lake, stream or river.
An unwanted organism is not managed under the ORC Pest Plan but may be controlled as part of our Biosecurity Strategy.
CHECK your gear for stowaways and remove the pests either at the site or put it in the rubbish bin. CLEAN your gear thoroughly (one way is to use 10% dishwashing detergent mixed with water and leave the item wet for 10 minutes, visit this page for more ways). DRY it for 48 hours before relocating to another waterway!