An updated ten-year management plan has been released to tackle lagarosiphon in Lake Wānaka, one of three plans designed to protect the lakes from one of New Zealand’s most invasive aquatic weeds.

The updated plans, prepared for Toitū Te Whenua Land Information New Zealand (LINZ) by Earth Sciences New Zealand (formerly NIWA), also cover Lakes Dunstan and Wakatipu.

They are tailored to reflect the unique conditions of each lake and, for Wānaka, the focus is on steadily reducing infestations that have plagued parts of the lake for decades.

LINZ biosecurity manager Tracey Burton said the local focus is to “make inroads clearing Lake Wānaka”.

Earlier this year LINZ installed more than 4.5 hectares of hessian matting in a recent effort to reduce the aquatic weed.

Read more: Big push to clear lake of lagarosiphon

“If left unchecked, lagarosiphon can form dense weed beds that smother native aquatic plants and restrict recreational access,” Tracey said. 

“With lagarosiphon currently confined to only a few lakes in the South Island, our updated management plans will help us stay ahead of the spread and ensure these iconic lakes remain healthy for people and nature, now and into the future.” 

The plans incorporate the latest research and best practices for controlling lakeweed, including hessian mats, divers hand-cutting weeds in high-use areas, aquatic herbicide, ongoing monitoring and surveillance, and public awareness initiatives to encourage lake users to check, clean, and dry their gear.  

They were developed in collaboration with stakeholders - the Wānaka plan was updated with the help of the Lake Wānaka Aquatic Weed Management Committee, which has members from LINZ, Otago Regional Council, the Department of Conservation, Queenstown Lakes District Council, Guardians of Lake Wānaka, Kāi Tahu, Wānaka Marina Limited, and Fish and Game.

“These plans are a great example of collaborative biosecurity in action,” Tracey said. “Everyone has a role to play in protecting our lakes, from government agencies to lake users.” 

PHOTO: Clare Toia-Bradley