Scientists have made a breakthrough in the battle against didymo, a noxious pest sometimes known as rock snot.
Researchers at the Cawthron Institute in Nelson have bred didymo, an invasive alga, in the laboratory.
Dr Susie Wood said the research took four years and will allow them to more accurately identify what conditions promote its growth.
They have already discovered some chemicals prevent didymo attaching to rocks - which could be used to manage the spread of the pest.
However, didymo will probably never be completely eradicated.