Weed scientists from Agriculture and Agri-Food Canada (AAFC) have completed evaluations on samples of kochia (Kochia scoparia) collected from three fields in Southern Alberta last August and have confirmed the first case of a glyphosate-resistant weed in Western Canada.
Two weed species in Canada were previously confirmed as resistant - all found in southwestern Ontario. Giant ragweed was confirmed in 2009 and Canada fleabane was confirmed in 2011. Glyphosate-resistant kochia populations have previously been confirmed in Kansas, Colorado and Nebraska. There are also suspected cases being investigated in North and South Dakota and Montana.
"We began this particular investigation of kochia in three chem-fallow fields in Southern Alberta last summer where we saw little-to-no kochia control after receiving multiple applications of glyphosate," explained Dr. Bob Blackshaw, one of two AAFC weed scientists working on this project. "That prompted us to do further work through the fall and winter that involved collecting samples of seed and completing the necessary grow out and spraying of plants to confirm resistance."
Blackshaw and fellow AAFC weed researcher, Dr. Hugh Beckie, completed tests on seed samples collected from the fields to validate their findings. The studies looked at the survival of the kochia plants at increasing rates of glyphosate, a standard protocol required for resistance confirmation.
Monsanto Canada worked cooperatively with the researchers to confirm the finding of resistance and will work together to begin developing recommendations for the impacted farmers, as well as other farmers in the region who may be looking for advice on the steps they can take to reduce the chances of the resistance spreading or developing in other fields.
What makes this particular case different from some of the previous situations where glyphosate resistance has been confirmed, is that it does not appear to have developed in a Roundup Ready(R) cropping system. The suspected weed species were found in three fields of chem-fallow and the typical crop rotation of the fields does not appear to have included regular use of Roundup Ready crops.
In recent years, Monsanto has elevated its focus on weed resistance management to protect the value that Roundup(R) brand herbicides and Roundup Ready crops have brought to western Canadian farmers. That focus has involved the production of several communication pieces and online tools aimed specifically at elevating awareness, educating growers and ultimately helping them reduce the likelihood of resistance developing on their farm.
"We devote a lot of research to explore practical and cost-effective solutions for growers who are faced with glyphosate-resistant weeds on their farm. We have been fortunate in Canada in that this is not a large scale weed management issue," said Sean Dilk, technology development manager within Monsanto's crop protection division. "But we have increased communication around this topic and we speak to farmers about this more often to lessen the likelihood of resistant weeds developing. It's part of our commitment to stewardship and protecting a valuable tool that farmers have come to rely on."
Resistance evolves after a weed population has been subjected to intense selection pressure in the form of a repeated use of a single herbicide and without adequate incorporation of cultural weed management options. The herbicide controls all the susceptible weeds, leaving only resistant plants to reproduce.
While glyphosate-resistant kochia has now been confirmed, the AAFC weed scientists are continuing their work on this particular site. Monsanto Canada is also supporting the AAFC research effort which includes providing recommendations to help farmers manage glyphosate-resistant weeds once they are identified and confirmed.
In addition to the work being undertaken by AAFC, there is ongoing collaborative research being conducted with academics such as Dr. Linda Hall at the University of Alberta for specific solutions that will address glyphosate-resistant kochia. AAFC, the University of Alberta, along with Monsanto are all working to develop and communicate a set of local solutions to slow or manage the populations that are currently under review.
"Our history tells us that farmers can, and are, effectively managing the situation with good agronomic practices such as using tank mixes and/or cultural weed control methods. We recognize this particular finding could present new challenges if it spreads because of the prevalence of Roundup Ready canola and Roundup Ready sugarbeets in this region," acknowledged Dilk. "But the effective use of Roundup agricultural herbicides and Roundup Ready crops has continued in areas where glyphosate resistance has occurred in the past and we have some very knowledgeable people looking into this issue. I am confident in our ability to present good options to the growers in the region."
Monsanto takes product stewardship and claims of glyphosate resistance seriously and encourages growers to report suspected cases of resistance to Monsanto representatives so they can work with academics and extension services to investigate suspected cases, develop solutions for farmers and communicate the findings broadly. Monsanto's current best management practices include:
- Start with a clean field by either utilizing a burn down herbicide or tillage to control weeds early.
- Tank mix effective herbicides with pre-seed Roundup applications before appropriate crops in the rotation.
- Include other cultural practices where appropriate as part of the overall cropping system.
- Use the right herbicide at the right rate and apply at the right time.
- Control weeds throughout the season to reduce the weed seed bank.
- Be sure to include other crops (including glyphosate-tolerant and non glyphosate-tolerant crops) in rotation with Roundup Ready crops to allow greater opportunity for the inclusion of other modes of action.
Farmers, who want to assess the likelihood of glyphosate resistance developing on their farm, can visit www.weedtool.com. They can also obtain additional information and stewardship recommendations in Monsanto's pamphlet, "Best Practices for Weed Management: Start Clean and Stay Clean."
"Glyphosate has likely delayed the evolution of weed resistance to other herbicides and mitigated their resistance impact," explains Dr. Beckie. "However, farmers need to think carefully about how and when they use glyphosate."