Weed Management Research

Herbicide resistant weeds are a real and increasing issue globally and evident in New Zealand. Herbicide resistant ryegrass is for example, a problem in both arable farms and vineyards.

We are working with Trevor James and AgResearch in a project focused on improved weed control and vegetation management to minimise future herbicide resistance. The project is funded through the Ministry of Business, Innovation and Employment (MBIE) and major co-funder, the Foundation for Arable Research (FAR).

The project has four main work areas:

Anticipating herbicide resistance

A Lincoln University team is seeking to predict likely herbicide-resistant weed assemblages worldwide and identify weeds most likely to develop herbicide resistance in new regions. The world-wide mega-database of herbicide resistance will be used to create a matrix of 100 regions and 200 weeds for each major herbicide group. Those relevant to New Zealand will be ranked on their likelihood of occurring in New Zealand. Outputs will be a risk index that indicates a) weeds currently in NZ with a history of herbicide resistance elsewhere in the world pose the greatest risk to our agriculture b) herbicide resistant weeds currently absent from NZ that pose the greatest risk of establishment if unintentionally introduced here and c) weeds worldwide that have a high likelihood of becoming resistant in the future and the risk they pose to NZ.

Understanding and influencing drivers of herbicide practices

The AgResearch People and Agriculture team seeks to identify and describe the systemic drivers of on- and off-farm herbicide practices to influence and change behaviours. They are working with key stakeholders (Māori, farmers, national sector players and international experts) to identify and leverage opportunities to more successfully address factors across the supply/value chain that restrict or hinder change.

Identifying instances of resistance and their impact

Grasslands and Massey University researchers will develop superior new ways to rapidly identify resistant plants. This will use genotyping and seed bioassays to create ‘quick tests’ for key weed species. They will also model spread scenarios for resistance genes to determine the greatest risk of resistance i.e. from on-site resistance evolution or from dispersal of resistant weeds. They are starting with perennial ryegrass before adding other species for screening.

Managing herbicide resistant weeds

We are in the team led by Trevor James looking to develop new non-herbicidal interventions (e.g. robotic weeders, abrasion technologies and smart cultivators) and the use of cover crops (in collaboration with FAR) for both managing existing and avoiding new instances of herbicide resistance.

Included in this section is ‘rediscovering’ Māori management practices such as traditional strategic resting and natural pathogenic organisms to target the soil weed seed bank). While virtually all our problem weeds are introduced from Europe and the Americas, the holistic approaches typical in Māoridom seem fully relevant to a systems based approach to weed management. A second group in this team is to isolate and evaluate natural pathogenic fungi and bacteria for their ability and efficacy to kill weed seeds.

LandWISE members are well-aware of the risks of herbicide resistance. It has been an aspect of LandWISE projects since the early 2000s when we began promoting strip tillage and no-till systems to maintain soil quality and reduce energy inputs. The extra pressure on herbicide controls when physical cultivation is reduced saw us publish charts of herbicide groups for different crops. Maybe it is time that work was brought up to date!