Resistance Management School: Seeding rates to the rescue


Highly competitive crops that make it difficult for weeds to gain a foothold in fields play a key role in effective herbicide resistance management.

One way to make your crop more competitive is to increase seeding rates to produce higher plant populations. In this episode of RealAgriculture’s Resistance Management School, University of Manitoba weed scientist Rob Gulden discusses how growers in Western Canada can pump up seed rates to tackle troublesome weeds like glyphosate-resistant kochia and Group 1 herbicide-resistant wild oats.

A more competitive crop reduces selection pressure for herbicide resistance, says Gulden. “And if a producer already has herbicide-resistant weeds, the crop is much more able to deal with those in case a herbicide is used that doesn’t control them.”

Kelvin Heppner interviews Rob Gulden at Crops-A-Palooza in Portage la Prairie, Manitoba. Story continues below the video.

Gulden notes that the latest Manitoba herbicide resistance survey reveals that four out of five fields in the province contain a Group 1 resistant wild oat population. “These weeds are very common and herbicide options, depending on the crop we’re in can be very limited,” says Gulden. “A higher-density crop will suppress those weeds, compete with them, and those weeds will produce fewer seeds.”

Check out Episode One of the Resistance Management School

With fewer resistant weed seeds in the seed bank, farmers are better positioned to control the spread of resistance, but higher seeding rates do cost money. In crops like canola, farmers have migrated to lower seeding rates to cut costs.

Gulden agrees that modern canola hybrids perform well at 60 plants per square metre (about six plants per square foot), but below this threshold, even with perfect weed control, there are yield limitations. Gulden also notes that greater plant density does deliver higher yield when combined with strong weed control. And that’s also a recipe for effective weed resistance management, he says.

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