Lakeweed control to kick off on Otago lakes

Work to control the invasive lakeweed lagarosiphon in Lake Wānaka and Lake Dunstan will start next 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 says the work is 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. 

“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. 

“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.”

Control efforts in Lake Dunstan will be quite different, as lagarosiphon is much more established, says Burton. 

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

Over the coming weeks, work will also begin in the Upper Kawarau River. 

More control efforts across the lakes will 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.”

LINZ is working closely with a number of groups, mana whenua and the community to help stop the spread of lagarosiphon in the region. This includes the Lake Wānaka Lagarosiphon Management Committee and Lake Dunstan Aquatic Weed Management Group, which are led by LINZ. 

Burton says lake users also have a key role to play in helping protect our lakes from lagarosiphon, which is 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.