The lakeweed lagarosiphon can smother native plants, choke waterways and disrupt recreation.
Divers have started hand-weeding and monitoring in Lake Wakatipu.
The efforts are part of Land Information New Zealand’s annual biosecurity programme, which also includes upcoming work in Lake Wānaka, Lake Dunstan and the Kawarau River, as well as in South Canterbury and Waikato.
LINZ biosecurity manager Tracey Burton said the invasive weed “could have significant environmental, economic and recreational impacts”.
She said one of the biggest risks of spreading the weed into the lake was boats travelling from the Kawarau River.
“We ask boat users to do their bit by turning off their engines at the checkpoint just below the Kawarau Falls Bridge.
“This simple action helps dislodge any weed fragments and prevent them from entering the lake,” she said
Control works will take place at Lake Dunstan from mid-November and Kawarau River in late November.
Further control efforts will take place across the lakes between February and May 2026.
