By Top Crop Manager
Multiple modes of action make a big difference when it comes to slowing down the development of herbicide-resistant weed populations. That’s the message echoed throughout Nufarm Agriculture’s field plot tour, held outside Saskatoon on July 5.
The tour featured cereal, canola, soybean and pulse plots to demonstrate Nufarm’s line of herbicides for pre-emergent control in cereals, canola, soybeans and pulses, and in-crop weed control in cereals. The overriding focus was on strategies to reduce the risk of weeds developing resistance to herbicide groups.
“Using multiple modes of action across multiple application timings helps to manage the selection pressure placed on weed populations by each individual mode of action, and can reduce the proliferation of resistance mechanisms through a weed population,” says Nufarm’s Technical Services Manager Graham Collier in a press release.
Agriculture and Agri-Food Canada research scientist Dr. Hugh Beckie updated attendees on the state of herbicide resistant weeds in Western Canada. Dr. Beckie, who worked on the very first case of herbicide resistance back in 1988, said the issue is growing in both complexity and severity. “In 2003 we were seeing 10 per cent of fields impacted, and as of last year we were seeing 57 per cent,” he said. Herbicide resistance hits farmers right in the pocket book, Dr. Beckie explained, citing a recent survey of 300 sites in Saskatchewan that found farmers reporting extra costs of $15-20 per acre to address herbicide resistance.
Weed resistance is a growing challenge for all growers, but how likely resistance is to develop isn’t a mystery. Collier reviewed the key factors that impact herbicide resistance development. “Herbicide resistance can increase exponentially in a field, year by year, depending on the herbicide mode of action, the selection pressure applied to the population, the biology of the weed, and the number of times a specific mode of action is used,” says Collier. “For example, resistance will spread through a kochia population much faster than a wild oat population due to cross pollination, seed production and seed bank longevity. “
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