Managing Herbicide Resistance

April 20, 2018

Herbicide resistance poses a challenge to agricultural productivity and profitability. It’s an issue facing all growers, but increased awareness and adoption of best practices can help to minimize the impact in your fields.

Chadrick Carley, Syngenta’s agronomic services manager, Western Canada, attended the recent Herbicide Resistance Summit in Saskatoon, Saskatchewan to build his knowledge on the growing threat. The bi-annual conference hosted by Top Crop Manager was intended to increase understanding of herbicide resistance and promote awareness that everyone has a role to play in managing it.

“It’s important to keep up with current issues that growers are facing and researchers are investigating,” says Carley. He reports that conference attendees included industry members and growers alike.

Think outside the box

The two-day event featured presentations by leading researchers. Two presenters who stood out to Carley included Peter Sikkema, professor of field crop weed management at the University of Guelph, Ridgetown Campus, and Tom Wolf, founder of Agrimetrix Research & Training in Saskatoon, Saskatchewan.

While Sikemma’s presentation ­– ‘Glyphosate-resistant weeds in Ontario’– doesn’t seem relevant to growing malting barley in Western Canada, Carley says the research and recommended best management practices are applicable across all crops and regions. “In the greater scheme of things, there are herbicide resistance management tools that everyone can benefit from. Look for options outside the box and put them into practice.”

Having had the chance to digest everything he heard at the Summit, Carley says the message he wants to share with growers is: “look at every crop as a potential to manage resistance. Every crop has a chance to rotate a herbicide, increase your seeding rates, or anything that you can do, be it chemical or cultural control, to help manage resistant weeds.” 

Carley says that planning rotations – both crop and herbicide ­– is key. “Don’t use the same herbicide group repetitively,” he says. The first weed that comes to mind in malt barley production is wild oats, which requires a Group 1 (or maybe Group 2) herbicide for control. “Plan which wild oat herbicide you want to use in your barley versus other crops. For example, try to limit the use of a Group 1 herbicide on your canola or peas when you have the option to use other groups in those crops.”

Cereals like malting barley are great rotational crops because they are very competitive and, in combination with higher seeding rates and good herbicide efficacy, you'll reduce the amount of weeds that emerge after application. Growers should consider this advantage as part of their resistance management strategy.

Application techniques can help delay resistance

A presentation by Wolf (aka ‘The Nozzle Guy’) provided some enlightening information on ‘Managing resistance with sprayer application technology.’ What does herbicide resistance have to do with application technology? According to Wolf, research conducted in the U.S. shows that under dosing can be a source of herbicide resistance. Fortunately, growers can make application tweaks to ensure weeds receive an accurate rate of herbicide.

“It was such a different way of looking at herbicide resistance,” says Carley, adding that herbicide resistance management discussions typically focus on the need for new active ingredients as a solution. “I like the message of striving to do a better job applying the actives that we currently have to delay resistance.”

Wolf’s research shows there are areas in the field where we're over and under applying herbicides. This is largely due to the mechanics of the sprayer (e.g. boom height, boom swing) and tractor speed.

His work also shows that consistency across the sprayer isn't as uniform as a grower may believe. We're doing quite well at applying ‘x amount of water’ over ‘x amount of acres,’ but the distribution may not be consistent. For example, if we wanted to do 10 gallons an acre, we were getting 10 gallons an acre on the field, but some areas may see 6 gallons and some may see 12 gallons.

So what’s the solution? “Slowing down helps a lot of things,” says Carley. “It’s something within a grower’s control because they’re the ones controlling the speed of the sprayer and setting the boom height.”

View all of the presentations from the 2018 Herbicide Resistance Summit here.

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