Work to control the invasive lake weed lagarosiphon in Lake Dunstan starts this week.

The control efforts, which are ongoing until mid-December, are part of Toitū Te Whenua Land Information New Zealand’s (LINZ) annual Otago Lakes biosecurity programme.

LINZ biosecurity manager Tracey Burton said the work was essential to ensure the health of the lakes and allow people to enjoy them this summer.

“Left uncontrolled, lagarosiphon can take over lakes, choke waterways, smother native aquatic plants and impact how we use our lakes.’’

Control efforts in Lake Dunstan would be quite different to work in Lake Wanaka, as lagarosiphon was much more established, Tracey said.

“Divers will control the tall, dense weed around high-use areas, including boat ramps and swimming areas, to prevent it spreading further.”

“In Lake Wānaka, divers will be checking eradication zones north of Roy’s Peninsula, as well as carrying out maintenance, such as fixing any wear and tear on hessian mats in the western bays. 

“Eradication zones are where invasive weeds have been completely cleared, and divers will focus on removing the odd weed that may have reinfested the area,’’ she said.

“The maintenance work will build on the progress made in previous years around Parkins and Paddock Bay.

“Ultimately, we’re hoping to clear lagarosiphon from the lake.”

Work in the Upper Kawarau River would also be undertaken in the coming weeks

More control efforts across the lakes would take place between February and May.

“Without funding support from Contact Energy, Otago Regional Council and Queenstown Lakes District Council we wouldn’t be able to carry out this vital work,’’ Tracey said.

LINZ was working closely with a number of groups, mana whenua and the community to help stop the spread of lagarosiphon in the region. 

This included the Lake Dunstan Aquatic Weed Management Group and the Lake Wānaka Lagarosiphon Management Committee, which are led by LINZ.

Lake users also had a key role to play in helping protect our lakes from lagarosiphon, which was easily spread between waterways.

“A tiny fragment the size of a fingernail caught on any gear is all it takes to spread lagarosiphon from one area to another.

“If you are heading out on the water, please check, clean, and dry all your gear – especially if you’re moving between waterways.”

The ‘’Check, Clean, Dry’’ campaign is led by the Ministry for Primary Industries in partnership locally with Otago Regional Council. 

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