Grainswest - Tech 2022

Tech 2022 grainswest.com 39 While much research has been conducted on methods to control problem weeds such as kochia and wild oat, most still involves the use of herbicides. “You’re not going to spray your way out of resistance,” said TomWolf of Agrimetrix Research & Training. It’s a maxim the professional agrologist uses often. So where does that leave farmers? Wolf, along with industry experts Charles Geddes, Eric Johnson and Matt Gosling, offer advice for management of herbicide resistance, and where possible, include non-chemical options. A GROWING PROBLEM As part of an ongoing survey that began in the early 2000s, Agriculture and Agri-Food Canada (AAFC) research scientist Geddes has surveyed farms across the Prairie provinces for several years to better understand resistance issues. The recently completed Saskatchewan survey found resistance in 74 per cent of the 419 fields tested in 2019 and 2020. A survey will be conducted in Manitoba in 2022 and in Alberta in 2023. According to the last round of surveys led by AAFC’s now-retired Hugh Beckie between 2014 and 2017, herbicide- resistant weeds are found on more than half of Prairie fields. It’s difficult to determine what herbicide resistance costs the industry. In management questionnaires between 2014 and 2017, Western Canadian farmers estimated its total cost in yield loss or expenses incurred for additional weed control amounted to $13 per acre for a yearly total of $530 million. While resistance has not grown exponentially, the agronomic practices being employed are not enough to slow its spread. “Roughly, we’re seeing about two new biotypes of herbicide-resistant weeds showing up in Canada each year,” said Geddes. “What that means is we’re continuously seeing selection pressure or new types of resistance showing up. And, of course, these resistant weeds are evading herbicide applications and resulting in crop yield losses among other detrimental effects.” Group 1-resistant wild oat is by far the most common problem across the Prairies, said Geddes. Much of his work, though, focuses on Canada’s second biggest weed of concern, Group 2-resistant kochia. There is a range of post-emergent herbicides that are effective against kochia, but rapid selection for resistance is taking place. Other glyphosate-resistant weeds are beginning to show up now, too. Southern Alberta, for instance, documented its first case of glyphosate-resistant downy brome last year. As far as anyone knows it’s the only such case in Canada, but Geddes noted full surveys in Manitoba and Alberta have yet to be conducted. “Obviously, that has pretty significant CHEMISTRY AND BEYOND New approaches to herbicide resistance BY MELANIE EPP ILLUSTRATION BY ADAM NIKLEWICZ I n Western Canada, the threat of herbicide resistance has grown like a weed in recent years. Behind the United States and Australia, Canada has the third greatest number of unique herbicide-resistant weed biotypes. The number of weed species in this country that have developed resistance has grown steadily since the 1970s and stands at about 80. No new meaningful modes of action have been introduced since the 1980s, and the selection pressure that produces resistance is expected to continue.