A Toitū Te Whenua — Land Information New Zealand (Linz) spokeswoman said divers located the invasive lake weed and used a pipe to remove the plant, including its roots, pumping it to the surface and collecting it in bags for disposal.
This season’s control work started in October and was expected to be completed by the end of June or mid-July.
"Our divers also carry out regular surveillance in cleared areas to ensure the weed has not reinvaded," the spokeswoman said.
The Otago Regional Council website says the fast-growing freshwater pest plant is found in Lakes Dunstan and Roxburgh and parts of Lake Wānaka.
Lagarosiphon was once sold as a decoration for aquariums or ponds and is believed to have been accidentally introduced to waterways through disposal into drains or ponds, it says.
