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What are the odds of glyphosate resistance?

Glyphosate-resistant kochia is currently isolated to a small area in southern Alberta, but farmers should be conscious of the fact that it could spread. “Resistance is a numbers game,” says Clark Brenzil, Saskatchewan Ministry of Agriculture weed specialist. “When a resistant biotype either gets brought in from somewhere else or evolves on the parcel of land that it’s on, what happens is you have got one plant in perhaps a billion, but it always starts with one very, very rare plant.”

A herbicide resistant biotype can percolate along, unnoticed for several years, gradually building up as a proportion of the population. Once it gets to the point where the farmer notices it, it has probably already been through the combine a number of times and spread throughout the field. “Producers need to manage for minimalization, because as long as your resistant weed population is a very, very small proportion of the total population it’s not a production concern, but you want to keep it at a level where you can’t see it. If resistance evolves to the point where a producer can see it in his field, the game is pretty much over for that particular herbicide group. He’s got two years left before it’s field wide.”

Farmers should also resist the temptation to become too complacent about weeds that have already developed some resistance elsewhere. “A big key to beating resistance is to resist the impulse to break away from your herbicide rotation in order to save a couple of bucks one year,” says Brenzil. “Once you do it one year and don’t see any resistance showing up, it’s tempting to get trapped in that cycle of repeating that over and over again, and eventually you get to the point where kochia is at right now with Group 2 resistance. Group 2s were a great herbicide on kochia but they aren’t any more. So we have now lost that tool and there are a finite number of tools in the toolbox.” †

About the author


Angela Lovell

Angela Lovell is a freelance writer based in Manitou, Manitoba. Visit her website at or follow her on Twitter @angelalovell10.



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