Canola School: Managing herbicide resistance through spray management

Often when we think of herbicide resistance, as producers, we think it means we have to stop spraying certain products completely.

This is not always the case, and as Tom Wolf of Sprayers 101 and AgriMetrix explains in our latest Canola School episode, why and how you can take some extra steps from the sprayer to mitigate resistance.

There are dioecious weeds — which means in order to spread, they have to cross pollinate — that are moving west from Ontario and north from the U.S., and making their way into the Prairies, such as waterhemp. According to Wolf, these weeds are susceptible to developing what’s called polygenic resistance.

“This means some of these weeds might be a little more tolerant of the herbicide. And if they also cross with other plants that are equally or slightly more tolerant, their offspring are more likely to be more tolerant. Move that forward a few generations, you end up with something that’s pretty close to resistance,” he explains.

So how do we tackle this? How can we manage these weeds before we get to the point of resistance? Wolf says the key is to stay on top of these weeds before they are able to cross pollinate.

“The whole concept of this is to let no weeds survive. That means we have to look and go ‘Ok, where in our field and under what circumstances do we have these sublethal doses?’,” says Wolf. “The most powerful tool we have is to make multiple effective modes of action tank mixes.” The classic example of this throughout Western Canada is where we have kochia that is resistant to glyphosate — with the potential of other weeds following — is to spray two additional modes of action that are known to kill kochia.

The multiple modes of tank mixes can get expensive, but as Wolf explains, it will pay off in the long-run. The other way producers can help cut costs is through the use of an optical sprayer, such as the WEEDIt system. This will allow you to spray the weeds only where they are present, which can also combat resistance in itself.

“You might save 60-70 per cent of your total burn-off bill, which makes a multiple effective modes of action affordable. And that, in turn, delays the onset of resistance. I think that’s a pretty important strategy,” says Wolf.

When it comes to resistance, Wolf says our days are numbered, so taking any sort of action that will prolong the use of the tools we currently have will be crucial to the future success of our industry.

Check out the full conversation between Tom Wolf and RealAgriculture’s Kara Oosterhuis in our this Canola School episode:

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