The Battle of Resistance - PulseResearch
April 25, 2017
Developing management options for herbicide-resistant weeds in pulse crops
]In a recent phone survey undertaken by Saskatchewan Pulse Growers (SPG), famers indicated that weed management was a top concern for their pulse crops, specifically those with Group 2 herbicide resistance.
The prevalence of these weeds is a known problem in the Canadian prairies, stemming from an overreliance on Group 2 herbicides due to a lack of alternative product options. This has caused weeds to develop resistance much quicker than they usually do and, according to Eric Johnson, Weed Biologist with Agriculture and Agri-Food Canada, there are now more than 20 weed species in the Canadian prairies identified as being resistant, with the most concerning ones being kochia, wild mustard, and cleavers.
Johnson is currently working on a solution to the problem via a two-part research project, funded by SPG, which aims to identify alternative modes of action for weed management and to help make them available in Saskatchewan. The first phase of the project, now complete, investigated potential herbicide candidates, including flumioxazin (Group 14), fluthiacet-methyl (Group 14), pyroxasulfone (Group 15), and propyzamide (Group 15) for alternative modes of action in weed control, taking into consideration the impact of soil type and climatic diversity on the herbicide’s performance. From this research, Johnson made some valuable discoveries including that a fall application of flumioxazin helped to control winter annual weeds (including narrow-leaved hawksbeard) and early spring flushes of kochia, indicating it could be effective in managing glyphosate-resistant kochia that emerges prior to seeding pulses. It was also determined that fluthiacet-methyl, a post-emergence product, worked with tank-mixes including imidazolinone herbicides to control resistant kochia and wild mustard in Clearfield® lentil and other pulses. Johnson also discovered that pyroxasulfone demonstrated activity on wild oats and cleavers, and that propyzamide demonstrated good control of kochia and wild oats with acceptable crop tolerance in lentils and field peas; this effect improved when combined with ethalfluralin.
The second phase of the research, now being carried out, involves two objectives. The first is to obtain the information necessary to register these compounds for use on pulse crops in Saskatchewan, including the best timing, adjuvants, and formulation for treatments. The second is determining a pre- and post-emergence herbicide strategy for controlling cleavers in field peas in the black soil zone, as well as identifying tank-mix options to control glyphosate-resistant kochia before seeding.
“Our goal is to determine a combination pre and post-strategy to provide consistent cleavers control in higher organic matter soils,” Johnson says. “In terms of the pre-seed burnoff of glyphosate-resistant kochia prior to seeding pulses, we are trying to introduce another mode of action, so we are not just reliant on Group 14s as tank-mix partners.”
Johnson’s goal is to have the project completed by 2017 and to be able to offer growers alternative solutions to their herbicide problems as a result. “We hope that, by that time, registrations for flumioxazin, pyroxasulfone, and fluthiacet-methyl will be submitted or approved for registration,” he says.
SPG Investment: $80,490
Co-Funders: Alberta Pulse Growers and Agriculture and Agri-Food Canada (collectively $221,472)
Project Lead: Eric Johnson, Weed Biologist with Agriculture and Agri-Food Canada