Don’t forget to check for didymo this summer


People going near a river or stream this summer are urged not to forget to ‘Check Clean and Dry’ as part of the normal practice of cleaning equipment.

Don’t forget to check for didymo this summer
‘Check Clean and Dry’ this summer.

Didymo is currently only found in South Island rivers and lakes where it can form a smelly mat. The Check Clean Dry campaign was started some years ago to prevent Didymo spreading northwards.

Didymosphenia geminata (didymo), also known as "rock snot" is a freshwater diatom (a type of alga) and was first reported in New Zealand in the Lower Waiau River in 2004.

Didymo is currently found in over 150 South Island Rivers. Under the Biosecurity Act 1993, the entire South Island is a Controlled Area. This means people are legally obliged to prevent the spreading of didymo.

Didymo is a microscopic pest that can be spread by a single drop of water. Even if you can't see it you could be spreading it. Therefore to prevent the spread of didymo you must Check Clean, Dry your gear when moving between waterways, and treat every waterway like it is infected with didymo.

Didymo can attach itself to stream, river and lake beds by stalks, and can form a thick brown layer that smothers rocks, submerged plants and other materials. It forms flowing 'rats tails' that can turn white at their ends and look similar to tissue paper. As the 'tails' of the alga get longer they become white in colour.

The ‘Check Clean and Dry’ campaign is now also used to help prevent several weeds in North Island waterways from spreading further, including Hawke’s Bay’s own nasty plant – hydrilla.

Hydrilla is commonly called the world’s worst aquatic weed and in New Zealand is only found in the wild in four Hawke’s Bay lakes - Tūtira, Waikapiro, Opouahi and Eland - where it is being controlled by grass carp.

Only tiny fragments of weed are needed to spread a plant. Aquatic weeds can remain viable almost indefinitely if kept damp, and then grow and spread if they drop into another lake, stream or river from the bottom of a boat, trailer, fishing gear or even a tramping boot.

For suspected didymo finds, contact the MAF hotline 0800 80 99 66.

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