Nationwide project offers hope in war against weeds

(Clockwise from top left): Woolly nightshade, Sydney golden wattle, yellow flag iris, Chilean needle grass, Chilean flame creeper, old man's beard. Photos / Supplied

A coordinated national research project aimed at tackling six of New Zealand's most invasive weeds through biocontrol is expected to have far-reaching benefits for landowners and councils across the country.

The three-year, $3.2 million project is backed by the Ministry for Primary Industries' Sustainable Food and Fibre Futures fund, Manaaki Whenua – Landcare Research, and the National Biocontrol Collective (the Collective) – a consortium of regional councils, unitary authorities and the Department of Conservation.

"There's no doubt about it – weeds are a constant source of stress for landowners," chairman of the project's governance group, Phil McKenzie said.

Biocontrol had the potential to provide a longer-term solution at a time when more registered herbicides were being restricted by New Zealand's export trading countries, McKenzie said.

"Weeds are becoming resistant to herbicides, and New Zealand society is demanding more environmentally friendly farming practices."

The project has three workstreams. These are to:

• Advance biocontrol programmes for several high-priority weeds
• Monitor weed reduction in matured biocontrol programmes on productive land
• Develop a partnership for sustaining investment in weed biocontrol.

The project will focus on Sydney golden wattle (Acacia longifolia), Chilean needle grass (Nassella neesiana), old man's beard (Clematis vitalba), woolly nightshade (Solanum mauritianum), Chilean flame creeper (Tropaeolum speciosum), and yellow flag iris (Iris pseudacorus).

By completion, the project aims to secure Environmental Protection Authority approval for the release of new biocontrol agents for at least three of these six weed species.

Image 1 of 6: Yellow flag iris.

Weeds were a major threat to New Zealand's natural and productive ecosystems, and were costly to control, McKenzie said.

"Through this project we aim to safeguard our environment and save landowners and councils money by finding smarter ways to reduce herbicides and the labour needed for weed control."

Although biocontrol was expensive upfront to develop, collaborative cost-sharing models would make the development stage affordable, and the long-term benefits made it "well worthwhile," McKenzie said.

"We've got 15 regional councils co-investing in the project too, which enables regional priorities to be accounted for in selecting weeds to work on."

Biocontrol could be a long-term, cost-effective and sustainable weed management solution, MPI's Director Investment Programmes, Steve Penno said.

"By pooling our research efforts across multiple development streams, including adopting what's worked in previous biocontrol programmes, we'll be able to accelerate progress considerably."

Farmers needed more effective tools to manage these invasive weeds," Penno said.

"To be able to eradicate or at least substantially reduce some of our most persistent weeds would be a huge win."