Prepare to battle herbicide resistance

As spring approaches, the crop protection community is set to work with producers to help stem the tide of herbicide resistance, encouraging the use of multiple modes of effective action for weed control, rather than a single method.

The balance sheet may show it’s cheaper in the short term to use a single mode to control weeds, but such practices also promote the long-term threat of resistance. It's an issue in Eastern Canada and in the west and can affect generations to come.

“You want to keep your fields clean, but you also have to consider succession,” says Adam Pfeffer, Bayer Crop Science Weed Management Agronomic Systems Manager for Canada. “You want the family farm you hand down to be sustainable. So, you need to take measures to prevent weeds from coming in, not just treat them once they arrive. They might not be identified until they are a problem.”

Weed forecasts everywhere focus on resistance

Resistance is on the minds of weed control forecasters everywhere, as tolerant weeds spread through major agricultural regions across the country. 

Pfeffer says the main problem is overuse of single modes of action, along with the lack of new chemistries. No popular chemistries have been developed for decades, leaving producers with limited options.

Overuse of single modes of weed treatment can lead to herbicide resistance in crops - something experts say we need to avoid. Tweet this

For example, the trend is creeping down but Pfeffer notes an estimated 75 per cent of glyphosate used for pre-seed burndown on the Prairies is still applied singularly.

Most new tank mixes combine old chemistries which separately have already led to resistance, in some cases.

“Four-way resistance is now seen in some weed species, and that takes options away if you’re counting on bringing old products back to life,” Pfeffer says.

Can’t give in to weed pressure

Dale Cowan, senior agronomist with AGRIS and Wanstead Co-Op in southwestern Ontario, says successful management will require a broad range of approaches. These include tillage methods and precision agricultural technologies to optimize spray applications.

“Manage all aspects of crop production that allow the crop plants to get the best possible start, to make them as competitive as possible with weeds,” he says.

As well, Cowan cautions that Canada’s borders need to be protected against invasive species seeds arriving via used farm equipment that could be herbicide tolerant, such as palmer amaranth, which is a huge problem in United States soybean and cotton fields.

He says chemicals will continue to have an important role in weed management if they’re used wisely.

“We must be as vigilant as possible in the face of dwindling options,” Cowen says. “We need to help existing chemistry do its job by not overusing it. Think about the future – we have to look after this problem now.”

Bottom line

Producers can help stem the tide of herbicide resistance by using multiple modes of effective action. Caution against invasive species seed arriving from the U.S. on used farm equipment is also recommended.

Article by: Owen Roberts