Herbicide-resistant weeds are just the symptom

Is resistance the problem, or is it farmers’ dependence on chemistry?

For decades, the experts have treated the growing problem of herbicide-resistant weeds as something solvable by the next new chemistry or biological breakthrough.

But now more are stepping back and acknowledging it as a symptom of a much bigger issue in modern agriculture.

In fact, one of the world’s leading experts in managing herbicide resistance goes so far as to call it a sickness that threatens global food security. Stephen Powles, who heads up the Australian Herbicide Resistance Initiative at the University of Western Australia, has even given it a name — HOS (herbicide-only syndrome).

He was among several speakers at a summit recently held in Washington, D.C. who made a compelling argument that something has to change — and fast.

Despite decades of research and extension to raise awareness and promote better management practices, the list of resistant weeds continues to grow and their grip on farmers’ fields continues to spread. In some southern U.S. states, farmers are returning to tillage — which most agree has ominous implications for soil health and future productivity.

A British weed specialist recently brought a chilling message to Prairie farmers about the difficulty and cost of controlling herbicide-resistant black-grass in Europe. Farmers there are resorting to older, more residual products that are tilled into the soil, a practice now being promoted here.

In Western Canada, a 2012 survey estimated weeds resistant to one or more herbicides had infested 7.7 million hectares.

Powles said the rising incidence of weeds that are resistant to multiple modes of action is evidence that farming’s dependence on chemistry alone is unsustainable.

It is a threat to global food security as it mainly affects farmers in the world’s top exporting countries, he said. Farmers in lesser developed countries still retain a higher degree of diversity in their farming systems and are less likely to use herbicides.

The Washington event, sponsored by the Weed Science Society of America, turned to some unlikely resources for advice — sociologists.

“Fundamentally, at its core, it is a problem of human behaviour — it’s the choices you and I have been making,” said David Shaw, chair of the society’s Herbicide Resistance Education Committee.

“Do you know what the definition of insanity is? It’s continuing to do what we have been doing, expecting different results.”

As the speakers at this event pointed out, the discussion over herbicide-resistance management needs to move beyond raising awareness and telling farmers what to do about it.

Farmers are aware. The latest poll by BASF of farmers’ attitudes found 82 per cent of Alberta farmers are worried about herbicide resistance, and 40 per cent think they already have it.

The things needed to avoid it are well documented. Yet many are waiting until they have the problem before taking action — and then it’s too late. Once weeds have evolved resistance, there is no going back.

In sociological terms, HOS is considered a “wicked problem,” which means it has multiple and complex causes that defy simple solutions, said Raymond Jussaume, head of sociology at Michigan State University.

Farmers’ management decisions are driven by multiple factors including financial, but also time management and peer pressure. Moving away from a herbicide-only approach as a prevention measure requires an upfront investment, yet the returns are delayed and intangible.

Addressing this requires all the players in the system to take ownership and move as a community towards a more holistic approach, he said.

Regulation is one of the options on the table. But far more effective is a community-based approach in which farmers help determine the goals and monitor progress, speakers said.

Herbicide manufacturers and distributors are already well aware of the threat of herbicides becoming redundant, which ultimately means no market for their product. Their message to rotate herbicides to prevent resistance is well taken.

But to keep them in the tool box, it will also mean using them less often. That message has been slow to sink in.

About the author

Vice-President of Content

Laura Rance

Laura Rance is vice-president of content for Glacier FarmMedia. She can be reached at [email protected]

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