Glyphosate-Resistant Kochia in Saskatchewan - PulseResearch
April 25, 2017
Surveys reveal how widespread glyphosate-resistant kochia is in Western Canada
In Western Canada, producers use glyphosate as a key herbicide for weed control. The frequency of use is not just limited to in-crop applications in glyphosate-resistant (GR) canola, corn, soybean, and sugar beet crops, but applications can occur prior to seeding as a spring burnoff, prior to or after a crop is combined for harvest management, as well as to control weeds in chemical fallow. Unfortunately frequent use is having some unwanted side effects and one of them is the growing resistance of kochia to glyphosate.
While kochia is the tenth most abundant weed across the Canadian Prairies, it is the fourth most abundant in the southern semi-arid grassland region. A competitive tumbleweed with early emergence, abundant seed production, and stress tolerance, kochia occurs in agricultural areas, wastelands, and rangelands, and is causing increasing problems for pulse growers.
To determine how widespread GR kochia is in Saskatchewan, Dr. Hugh Beckie, a research scientist with Agriculture and Agri-Food Canada, led a team of researchers to conduct a kochia survey similar to one conducted in Alberta, with funding from Saskatchewan Pulse Growers.
“Although GR kochia has been confirmed in Saskatchewan based on samples submitted by growers, its distribution and abundance in the province can only be determined in a random survey,” Beckie says. “A concurrent glyphosate-resistant kochia survey was conducted across southern Manitoba.”
The researchers conducted a stratifiedrandomized survey of 342 sites – one population per site – in southern and central regions of Saskatchewan. They collected mature plants, threshed the seed, and screened for herbicide resistance under greenhouse conditions.
“Screening confirmed 17 GR kochia populations in nine municipalities in westcentral or central Saskatchewan,” Beckie says. “As expected, based on previous survey findings, all populations were also resistant to tribenuron/thifensulfuron, an acetolactate synthase (ALS)-inhibiting (Group 2) herbicide.”
In the end, Beckie says, the cost-benefit of chemical fallow needs to be closely evaluated.
“GR kochia is strongly associated with chemical fallow, based on this survey and those in Alberta,” he says. “In the future, better cover crops where fallow is practiced would lessen selection pressure for GR and multiple-resistant weed populations.”
Kochia was only the first of several species predicted to be at risk for developing GR in Western Canada. Other abundant species selected during pre-seeding or in-crop/fallow applications are also at risk, including wild oat, green foxtail, cleavers, and wild buckwheat.
“Like kochia, these weeds have already been selected for resistance to herbicides with different modes of action used in-crop,” Beckie says. “Worldwide, the incidence of multiple-resistant weed biotypes is increasing at an alarming rate. Across the Prairies, multiple-resistant weeds will continue to challenge growers, especially when one of those modes of action is glyphosate.”
Surveillance of GR kochia across Western Canada will continue through periodic surveys and testing of suspected samples submitted by growers each year. A sevenday seed assay may facilitate more timely confirmation of GR kochia, thereby aiding in resistant weed management.
“We expect GR kochia to rapidly spread across the Prairies, similar to Group 2 ALS inhibitor-resistant populations,” Beckie says. “During these surveys, it was common to see suspected GR kochia populations in fields adjacent to the survey-targeted field, suggesting seed spread via tumbleweed movement or by farm equipment.
“The ease of mobility of resistance genes from field to field demands a collective regional response in proactively or reactively managing this multiple-resistant weed biotype.”
SPG Investment: $13,500
Project Length: 1 year
Project Lead: Dr. Hugh Beckie - Research Scientist, Agriculture and Agri-Food Canada