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Didymo Precautions

Help stop the spread of Didymo

Didymo is an unwanted organism under the Biosecurity Act 1933

If you are moving items between waterways you could be spreading Didymo without even knowing it. Didymo is microscopic and can be spread by a single drop of water. So even if you can't see it, you could be spreading it.

Check and Clean

Soak or scrub all items (clothing and bike) for at least one minute with any of the following:


Dry the item(s) to the touch then leave for at least 48 hours before entering another waterway

didymo1.jpgBiosecurity New Zealand has strengthened Didymo control efforts with a South Island-wide Controlled Area, enhanced public awareness activity and a $1 million summer research programme into potential control tools, but personal responsibility remains the key tool in reducing its spread.

Biosecurity New Zealand Director Post-clearance Peter Thomson says the revised strategy still relies on all freshwater users doing the right thing: "Nothing we can do cancels the need to clean between waterways anywhere in New Zealand. It applies to everyone, everywhere, everytime."

The new Controlled Area replaces all existing Didymo Controlled Areas and came into on Friday 9 December 2005, making it a legal requirement to clean items that have been in contact with lakes and rivers when leaving the South Island and before entering another waterway.

Spot checks at entry and exit points will be conducted, and the need to clean with Biosecurity New Zealand-approved "soak-scrub" cleaning methods promoted.

Extending the Controlled Area to the whole of the South Island acknowledges how big this issue is. The idea is to get ahead, rather than play catch up. To restrict access locally every time a new river is found to be affected is not a sustainable option. Didymo could survive in more than half of New Zealand's waterways, but it is a risk that can be managed if people are responsible."

Mr Thomson says the strategy acknowledged several factors

"Public awareness is our main tool and that campaign is being strengthened. Didymo is still an unwanted organism, and it is an offence to knowingly spread it. Breaching the Controlled Area could also result in severe penalties," Mr Thomson says.