The work is led by Toitū Te Whenua Land Information (Linz) as part of its annual biosecurity control programme.
Linz biosecurity manager Tracey Burton said from today divers would be in the lake over the next two months working hard to build on progress made over the past 20 years to clear lagarosiphon from the lake’s shoreline.
"The initial focus of divers will be monitoring the weed-free part of the lake and hand-weeding any isolated plants," she said.
"They will then turn their attention to controlling the weed outside of the weed-free area, working their way away from the western side of the lake towards Roys Bay, near the township.
"In this part of the lake, divers will install around 4.5ha of hessian mats to smother the weed."
Hessian matting was first trialled in New Zealand in 2016 at Lake Wānaka and had been a game-changer for eradicating lagarosiphon.
The matting was biodegradable, disappearing after the job was done. Native plant regrowth was fast because native seedlings could grow through the weave of the hessian.
The ultimate goal continued to be eradicating lagarosiphon from the lake.
"We’ve made good progress over the last few years, and we’re excited to see what impact we can make this season," she said.
"We’re hopeful these efforts will enable us to clear the weed from more parts of the lake and enable us to move the containment line further towards the township as we push to progressively clear the lake."
The containment line represents the divide between weed-free areas in the lake and areas infested with lagarosiphon. At present it stretches from the southern point of the peninsula to the southern point of Bishops Bay.
The goal this season was to move the containment line further south to include Paddock Bay, Parkins Bay and Glendhu Bay in the weed-free areas, she said.
"Little by little we’re pushing the containment line out and we’re hopeful we can do that again with these continued efforts."
The community has also contributed to the success of containing the weed through checking, cleaning and drying their gear to prevent it spreading.
The control work will be carried out by Linz biosecurity delivery partner Boffa Miskell Ltd and was partly funded by Queenstown Lakes District Council. A Lake Wānaka lagarosiphon management committee, led by Linz, has members from the Otago Regional Council, Queenstown Lakes District Council, Department of Conservation, Fish & Game New Zealand, the Guardians of Lake Wānaka and WAI Wānaka. Lake users are asked to avoid the area. — APL
