Small changes, big benefits

Preventing the spread of herbicide resistant weeds does not have to be a daunting task, according to an expert.

“It starts with one field and it starts today,” said Kate Sanford Mitchell, project manager for North American canola, pulses and cereals at Bayer.

She said growers can make small agronomic changes one field at a time to help prevent Canada from going down the same road as the United States and Australia, where herbicide resistance has become a major headache.

“It’s little shifts in thinking, it doesn’t have to be all or nothing,” she said.

“It’s not about changing every practice on your farm. It’s changing little things here and there that you may be able to make work.”

For instance, a new study in the United Kingdom says delaying seeding is the most important thing a grower can do to mitigate the development of herbicide resistant weeds.

“It’s a revolutionary concept,” said Sanford Mitchell.

She believes growers should seed their worst field for weeds last. The weeds will have a chance to grow up in the spring and then can be controlled with a late pre-seed burn-down, tillage or a late spring frost.

The grower can then select a different field next year on which to delay seeding.

As well, a new study from Australia suggests that seeding wheat and barley crops in an east-west direction can halve the ryegrass seed set compared to crops seeded north-south because it reduces the sunlight available to the weeds.

Prairie growers can experiment with one field to see if that seeding pattern delivers the same beneficial results here.

The research is a big deal in Australia, where growers are spending an additional $13 per acre to control resistant weeds on top of their usual herbicide costs of $46 per acre.

The situation is worse in the southern U.S., where growers have been forced to abandon glyphosate tolerant crops altogether.

“It has increased herbicide costs on their farms three to four times, if not higher, especially with having to use residuals in front of their herbicides,” said Sanford Mitchell.

Canada ranks third in the world for the highest incidence of herbicide resistant weeds, behind the U.S. and Australia.

Researchers have identified 64 resistant weeds in Canada. Alberta has 23, Manitoba 22 and Saskatchewan 19. Sanford Mitchell said there are likely more because many farmers don’t realize resistant weeds are growing in their fields.

Growers in Western Canada who have glyphosate resistant kochia in their fields are forced to use a Group 4, 6 or 10 herbicide to combat the weed.

“Those herbicides cost at least double what glyphosate does, if not a little bit more,” she said.

Growers faced with Group 1, 2 or 8 resistant wild oats also have added costs and may be forced to use a pre-emergent herbicide, which can add $20 per acre to their herbicide costs.

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