Herbicide programs for control of glyphosate-resistant canola (Brassica napus) in glyphosate-resistant soybean

Abstract

Glyphosate-resistant (GR) canola is a widely grown crop across western Canada and has quickly become a prolific volunteer weed. Glyphosate-resistant soybean is rapidly gaining acreage in western Canada. Thus, there is a need to evaluate herbicide options to manage volunteer GR canola in GR soybean crops. We conducted an experiment to evaluate the efficacy of various PRE and POST herbicides applied sequentially to volunteer GR canola and to evaluate soybean injury caused by these herbicides. Trials were conducted across Saskatchewan and Manitoba in 2014 and 2015. All treatments provided a range of suppression (>70%) to control (>80%) of volunteer canola. All treatments with the exception of the glyphosate-treated control reduced aboveground canola biomass by an average of 96%. As well, canola seed contamination was reduced from 36% to less than 5% when a PRE and POST herbicide were both used. Moreover, all combinations of herbicides used had excellent crop safety (<10%). All PRE and POST herbicide combinations provided better control of volunteer canola compared with the glyphosate-only control, but tribenuron followed by bentazon and tribenuron followed by imazamox plus bentazon provided solutions that were low cost, currently available (registered in western Canada), and had the potential to minimize development of herbicide resistance in other weeds.

Volunteer rapeseed infestation and management in corn

“…Similarly, Mierau et al. (2020) found a 60% reduction in soybean yield with an infestation of volunteer canola at a density of 60 plants m −2 .…”

“…In a study conducted at Glyndon, Minnesota, Stachler and Luecke (2009) found that volunteer canola at 180 plants m −2 resulted in a nearly complete loss of sugar beet crop yield. Similarly, Mierau et al (2020) found a 60% reduction in soybean yield with an infestation of volunteer canola at a density of 60 plants m −2 .…”

Exploiting the resource-ratio (R*) hypothesis for weed management in legume crops: An example of volunteer Brassica napus in soybean

“…However, limitation of volunteer canola seed production in crops grown subsequent to canola is imperative to limiting persistence of this weed (Geddes and Gulden, 2018;Geddes and Gulden, 2021). Soybean and canola have similar herbicide resistance traits (Mierau et al, 2020). In western Canada, volunteer canola is the most abundant weed species present after post-emergence weed control in soybean (Leeson et al, 2017).…”

Burial Environment Drives Seed Mortality of Kochia (Bassia scoparia), Wild Oat (Avena fatua), and Volunteer Canola (Brassica napus) Irrespective of Crop Species

“…Resistance to multiple herbicide sites-of-action exacerbates the impact of kochia, wild oat, and volunteer canola on Canadian farms by limiting the herbicide options available for their management [ 5 , 6 , 7 ]. In the Canadian prairies, resistance to 3, 4, and 3 herbicide sites-of-action have been documented in kochia, wild oat, and volunteer canola, respectively [ 8 ].…”