Beckie: Glyphosate-resistant Kochia (Kochia scoparia) in Saskatchewan
Date: June 2014
Term: n/a
Status: Completed
Researcher(s): Hugh J. Beckie, Scott W. Shirriff, Chris Lozinski, Agriculture and Agri-Food Canada (AAFC) Saskatoon; Eric N. Johnson, Greg Ford, AAFC Scott; Christian J. Willenborg, University of Saskatchewan; Clark A. Brenzil, Saskatchewan Ministry of Agriculture
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: SPG, SaskFlax
Project Summary
Glyphosate is the most widely used herbicide in the world, and frequent glyphosate use has selected for glyphosate-resistant (GR weeds). In 2011 and 2012, surveys documented the occurrence of GR kochia in Alberta. In the fall of 2013, a survey was conducted across southern and central regions of Saskatchewan to determine the distribution and abundance of GR kochia. Screening confirmed 17 GR kochia populations in nine municipalities in west-central or central Saskatchewan, bringing the total to 14 municipalities in Saskatchewan. The agronomic and economic impact of this GR weed biotype is compounded because of consistent multiple resistance to acetolactate synthase-inhibiting herbicides. However, all GR kochia in Saskatchewan were susceptible to dicamba. Across the prairies, multiple-resistant weeds will continue to challenge growers, especially when one of those sites of action is glyphosate.
In western Canada, glyphosate is a key herbicide for weed control in chemical fallow, preseeding in zero-tillage systems, pre- and post-harvest control, and in glyphosate-resistant (GR) canola, corn, soybean, and sugar beet. Glyphosate is the most widely used herbicide in the world, and frequent glyphosate use has selected for GR weeds – currently 28 weed species in several countries, including eastern Canada. Until 2011, GR weeds had not been identified in western Canada.
In 2011 and 2012, surveys documented the occurrence of GR Kochia (Kochia scoparia) in Alberta. Kochia is the 10th most abundant weed across the Canadian prairies, but fourth most abundant weed in the southern semiarid Grassland region. GR kochia was first identified in Kansas in 2007, and is now present in nine states. To determine the geographical extent of this GR weed in western Canada, surveys similar to that conducted in Alberta in 2012 were needed in the neighbouring provinces of Saskatchewan and Manitoba in regions where the weed is abundant.
In the fall of 2013, a survey led by researchers from Agriculture and Agri-Food Canada (AAFC) was conducted across 342 sites (one population per site) in southern and central regions of Saskatchewan to determine the distribution and abundance of GR kochia. (Under a separate project, a concurrent GR kochia survey was conducted across southern Manitoba in 2013). Mature plants were collected, seed threshed, and progeny screened by spraying with a discriminating glyphosate dose of 900 g ae/ha under greenhouse conditions.
Screening confirmed 17 GR kochia populations in nine municipalities in west-central or central Saskatchewan. Together with the previously confirmed populations, GR kochia is present in a total of 14 municipalities in Saskatchewan. While the majority of GR kochia populations originated in chemical-fallow fields (10 of 17), some populations were found in cropped fields (wheat, lentil, GR canola) and non-cropped areas (oil well site, roadside ditch). During these surveys, it was common to see other kochia populations suspected to be GR in fields adjacent to the survey-targeted field, suggesting seed spread via tumbleweed movement or by farm equipment.
The frequency of glyphosate resistance in confirmed populations varied from 12 to 96% (Table 1). Differences may be due to the time since glyphosate resistance was selected or introduced (either via seed or pollen), the amount of glyphosate selection that occurred in that population over time, or recent treatments that removed susceptible individuals from the population.
Table 1. Percentage of plants in a population resistant (R) to glyphosate or tribenuron/thifensulfuron, and the habitat (CF = chemical fallow) and municipality where populations were located in Saskatchewan. All populations were susceptible to dicamba.
The agronomic and economic impact of this GR weed biotype is compounded because of consistent multiple resistance to acetolactate synthase-inhibiting herbicides. However, all GR kochia in Saskatchewan were susceptible to dicamba, an increasingly important auxinic herbicide used for control of this multiple-resistant biotype. Dicamba-resistant kochia has not been identified previously in western Canada, but has been reported in the midwestern USA. Effectiveness of alternative herbicides on populations of this multiple-resistant biotype were confirmed in greenhouse studies. The ease of mobility of resistance alleles from field to field demands a collective regional response in proactively or reactively managing this multiple-resistant biotype.
Surveillance of GR kochia across western Canada will continue in the future, through periodic surveys and testing suspected samples submitted by growers each year. Researchers expect GR kochia to rapidly spread across the prairies, similar to ALS inhibitor-resistant populations, and are watching with concern the increasing incidence of multiple-resistant weed biotypes. In the future, better cover crops where fallow is practiced would lessen selection pressure for GR and multiple-resistant populations. Across the prairies, multiple-resistant weeds will continue to challenge growers, especially when one of those sites of action is glyphosate.
Scientific publications.
Beckie, H. J., Gulden, R. H., Shaikh, N., Johnson, E. N., Willenborg, C. J., Brenzil, C. A., Shirriff, S. W., Lozinski, C. and Ford, G. 2014. Glyphosate-resistant kochia (Kochia scoparia L. Schrad.) in Saskatchewan and Manitoba. Can. J. Plant Sci. 94: in press.
Full Report PDF: Glyphosate-resistant Kochia (Kochia scoparia) in Saskatchewan