Research finds herbicide resistance is greater than expected

Herbicide resistance is emerging as a serious and growing threat to New Zealand’s food production, with recent surveys by scientists finding half or more of arable farms and vineyards in some regions have weeds resistant to commonly used herbicides.

AgResearch scientists, who are carrying out the first systematic approach to surveying for herbicide-resistant weeds in arable crops with funding from the Ministry of Business Innovation and Employment, say their results are often many times the levels of resistance that had been expected.

Furthermore, new resistant weed species are being brought forward, or discovered by the AgResearch scientists working alongside the Foundation for Arable Research (FAR) and the Bragato Research Institute, as part of the Managing Herbicide Resistance programme which began in 2018. Continue reading

New Zealand is losing the war against weeds

New research* highlights how the lack of success in controlling weeds on agricultural and conservation land is challenging New Zealand’s position as a global leader in biosecurity.

Weeds are costing the country billions of dollars every year.

In a state-of-the-art review of how weeds are managed in New Zealand, Professor Philip Hulme has called for a paradigm shift in our approach.

“Unfortunately, we have rather little to show for the vast amount of time and effort government and landowners invest in the management of weeds,” said Professor Hulme, of the Bio-Protection Research Centre based at Lincoln University. Continue reading

Radio NZ reports on biocontrol and the fight to eradicate bad weeds

Radio NZ has been reporting on the problem of weeds, both in native vegetation and on farms and orchards, and on the the Department of Conservation’s War on Weeds.

One interviewee was Hugh Gourlay, from Landcare Research, who discussed (here) his work as part of a team that works to find biocontrol agents to kill or knock back the worst weeds.

The work involves visiting the country of origin of a plant and hunting for diseases that infect it. The team is  also looking for insects that attack and eat any part of the weed, including the seeds, flowers, leaves or stems.

Hugh told Radio NZ it is sometimes possible to “knock a plant invasion on the head” with prompt action to hunt down and kill all the plants. Chemical control, using herbicides, is usually the next step, but at best it will “keep the problem at bay.” This leaves biocontrol as the best answer for widespread weeds.

Once potential biocontrol agents are identified they are imported into New Zealand and kept in strict quarantine, so they can be tested to see if they attack any plants other than the weed. “If they don’t attack anything else then we can look to release them.”

Describing some great biocontrol successes in New Zealand, Hugh cites St Johns Wort control in the 1960s as a “guiding light” success story. Ragwort (Jacobaea vulgaris), some thistle species and mist flower (Ageratina riparia) have had successful biocontrol agents introduced.

More recently, the broom gall mite and several species of beetle that attack Tradescantia have been showing great promise.

Darwin’s barberry is among Hugh’s recent projects.

“Darwin’s barberry continues to advance across the countryside in Otago and Southland. It takes over entire hillsides, and becomes quite a monoculture.”

Beginning in the early 2000s, the biocontrol team identified a seed weevil and a flower weevil in the plant’s native range in South America. The focus has been on the seed weevils, which have been released over two years.

Radio NZ’s “Our Changing World” recently featured a story about the wasp mite that is being investigated as a potential wasp biocontrol agent. It has also looked at the buddleia leaf weevil.