For Craig Shaw, herbicide resistance is a wreck waiting to happen.
“It’s manageable at the present moment, but I wouldn’t guarantee it will remain manageable moving forward,” said Shaw, who has widespread herbicide resistance on his farm near Lacombe.
“We’ve learned our lesson in terms of staying on top of weed control and making sure we don’t have wrecks, but it’s an ongoing battle to try to get ahead of that and get it back to a normal situation.
“It only takes one bad year, and then you can fight with that for five to 10 years after that.”
Shaw first noticed Group 2-resistant cleavers and chickweed on his farm several years ago — a “difficult situation” because of how common the Group 2 mode of action is in herbicides. But the herbicide-resistant wild oats he found three years ago are quickly becoming a bigger problem.
“With the wild oat issue, we’ve put winter wheat in there hoping that we could get enough crop competition that it could keep the wild oats in check so that we could get away from herbicides for a year. That didn’t work as well as we hoped.”
Shaw’s problem is a common one for Alberta growers, said federal research scientist Neil Harker. While certain areas of the province have issues with herbicide-resistant chickweed, cleavers, and kochia, wild oat is the most herbicide-resistant weed in the province. While most of the resistance is to Group 1 herbicides, wild oats is also a high risk for glyphosate, or Group 9, resistance, and more than 10 per cent of fields in Alberta now have Group 2-resistant weeds.
“Wild oat is the big one, and it’s widespread,” said Harker. “You can randomly go to any farm without looking for resistance in any cultivated field, and over half of those fields in Alberta will have a resistant wild oat.
“I’ve seen data from fields where there are no viable Group 1 or Group 2 herbicides that are effective anymore.”
Herbicide resistance is a global issue — a study released in 2015 by well-known weed scientist Ian Heap found more than 450 unique cases of herbicide resistance in the world, with over 60 in Canada.
“It’s in almost every state of the United States except for Alaska, and it’s in every province of Canada, too,” said Heap, lead organizer of the International Survey of Herbicide Resistant Weeds.
“It’s very widespread — it’s wherever we’ve got intensive cropping and herbicides being used.”
And the cause is “very clear,” said Harker.
“It’s herbicide overuse,” he said. “We’ve overused the same herbicides year after year, crop after crop. For Group 1 wild oat resistance in Alberta where over half of our fields have it, we’ve overused Group 1 herbicides.
“When people say, ‘We don’t really know why this is happening,’ that’s not true.”
For many growers, it comes down to “a lack of forward thinking,” said Harker.
“Basically what they say is, ‘Why would we make changes when we still have herbicides that work and when we can still grow the most high-returning crops?’” he said.
“I understand why they do it — they’re trying to recoup money from bad years to pay off land and equipment. They need good short-term economics, but eventually, if they don’t do some of the longer-term thinking, even their short-term economics won’t look good.”
With that mentality, herbicide resistance is “an inevitable thing,” said Heap. And producers can’t count on new modes of action hitting the market any time soon.
“Before when we were having herbicide-resistant weeds, we would see new herbicides come along quite quickly,” said Heap. “But since about 30 years ago, the new herbicides have dried up and now we’re running out of herbicide modes of action.
“They’re going to be in a situation where they won’t have any herbicides left to control their weeds. That’s a massive problem.”
That’s what happened to cotton growers in the southern U.S., where glyphosate-resistant palmer amaranth has reduced cotton acres from around one million acres five years ago to 200,000 acres today, leading some cotton producers to lose their farms.
“We have examples of that in cotton in the southern U.S. where farmers are out of cotton, or they’re paying more than three times what they used to pay for herbicides because their simple, cheap herbicide solutions aren’t effective anymore,” said Harker.
In some cases, cotton growers have moved to deep plowing or even hand-weeding because chemical weed control no longer works.
“We don’t want to get to that point if we can do other things first and prolong the useful life of our herbicides.”
So how can producers stop themselves from hitting that point?
“The key to solving weed resistance is trying to find ways to use herbicides a little less often or a little less intensely,” said Harker.
“That’s mostly done with diversity — diversity of crops and diversity of weed control methods.”
Shaw has done that on his farm, by “changing the different chemistries around and trying different modes of action to keep things in check.”
“We’ve had to use better planning in terms of how we use herbicides now,” said Shaw, who also has a broad crop rotation that includes winter wheat, spring wheat, canola, and pulses.
“I’m much more cognizant now of mixing chemistry in terms of application. If we do pre-seed burn-downs, usually we have some other chemistry in there besides just straight glyphosate.”
The trick is getting “aggressive” with your weed control as soon as you spot a problem, said Shaw.
“Our attitude has been proactive, and I think that’s critical that we get on it at the early stage,” he said. “If you don’t get on top of it early, you’ll find that you get to a stage where herbicides are no longer a control option.”
But that requires an attitude adjustment, he added, starting with a change in management practices.
“You may go after short-term gains, but the pain down the road isn’t worth it,” Shaw said of the canola-wheat rotation that dominates the Prairies.
“If you’ve got problem areas, you need to get aggressive in terms of your weed control options.”
Producers need to be proactive, he added.
“If we look at experiences from around the world, these issues are coming, and sadly they’re going to impact our bottom line and our profitability,” he said.
“If you don’t get on top of it right away, it gets too far out of hand, and then you’ve got serious issues. Don’t leave it until you’ve got an unmanageable situation.”