Lake Wanaka weed control progressing well

16 August 2007

Significant advances have been made in the effort to control the invasive aquatic weed Lagarosiphon major in Lake Wanaka.

Lake Wanaka Lagarosiphon Managers Committee spokesperson Russell McGeorge said the committee was very pleased with progress in the last year, with the weed largely under control at sites north of the "containment line" between Roys Peninsula and The Peninsula.

"More effort can now be focused on controlling lagarosiphon at sites behind the containment line at the southern end of the lake," said Mr McGeorge.

In the past year Land Information New Zealand contractors using suction-dredging and hand-weeding techniques have removed about 350 cubic metres of the weed over the course of 40 days on the water.

The dredged weed is being composted by farmers on neighbouring land, while the local gun club is using the weed as a soft landing for clay birds.

The fast-growing and easily spread weed, introduced in the 1970s, is considered a significant threat to the lake's iconic values. A comprehensive 10 year weed management programme was launched in 2005 with the aim of combating the weed and preventing its spread and accidental re-introduction.

Based on inspections and expert advice from the National Institute of Water and Atmospheric Research, a work programme for the next 12 months will see suction-dredging and/or hand-weeding of lagarosiphon in Glendhu and Roys bays, the western side of The Peninsula and Bishops Bay.

This week the herbicide diquat was used to bring under control dense weed beds in Paddock and Bishops bays and off Stevensons Island.

Clearing lagarosiphon from amenity areas such as boat ramps and jetties will continue as usual, while at-risk, historic and active sites outside the containment line will be checked with a view to manually removing any regrowth or re-infestation.

Mr McGeorge thanked landowners who provided access through their properties enabling the work to be carried out. He also thanked Lake Wanaka users for their support for the lagarosiphon management plan.

"The recent discovery of lagarosiphon in Lake Wakatipu is a wake up call for lake users, proving how easily the weed is spread. Boaties can do their bit by checking and cleaning their boats, trailers and other equipment."

The Lake Wanaka Lagarosiphon Managers Committee is comprised of representatives from Queenstown Lakes District Council, Otago Regional Council, the Department of Conservation, the Guardians of Lake Wanaka, and Land Information New Zealand.

Media enquiries:

Dave Chowdhury
Senior Communications Advisor
DDI: 04 496 5402
Mobile: 027 222 9566
Email: dchowdhury@linz.govt.nz