COVID-19 Alert Level 2 information

See information and updates relating to Council services during Alert Level 2 - many Council facilities are now open, including our offices and customer service centres.

Share this page



Didymo infestation covering a whole riverbed.
Didymo covering rocks in a riverbed.

Didymosphenia geminata (didymo), also known as rock snot is a freshwater diatom (a type of alga). Didymo is currently found in a number of South Island rivers.

The Ministry for Primary Industries has declared the entire South Island a Controlled Area for Didymo. This means waterways are open to recreational activities, but people are legally obliged to prevent the spreading of didymo.

Check, clean, dry

CHECK: Before you leave a river or lake, check items and leave debris at site.

CLEAN: There are several ways to kill didymo.

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

Further Information

Go to the MPI website for more information on didymo