High Quality Content by WIKIPEDIA articles! In 2004 Didymosphenia geminata, a diatom commonly known as didymo or rock snot, was discovered in New Zealand, the first time it was found in the southern hemisphere. To restrict its spread, the whole of the South Island of New Zealand was declared a controlled area in December 2005. All items, such as boats, fishing gear, clothing, and vehicles, that have been in a stream, river or lake, must be cleaned before they enter another waterway. Biosecurity New Zealand working with Environment Southland, AgriQuality and Fish and Game launched an extensive public awareness campaign to encourage river users to clean their equipment after use in affected waterways. This campaign was highly successful, with 99% of freshwater users surveyed in 2008 in the South Island being aware of didymo.