Integrated weed management fails to impress

A variety of reasons are given for producers’ reluctance to adopt the strategy: cost, complexity, risk and peer pressure

Francois Tardif had an ear infection a few years ago, so the University of Guelph weed scientist went to the doctor.

“We got them (ear infections) when we were kids and we don’t remember, which is a good thing,” he told the CropConnect conference in Winnipeg earlier this month.

“It’s terrible.”

When describing the pain to his doctor, Tardif told her, “it hurts like crazy.”

“She didn’t say, ‘well, let’s talk about the principles of integrated ear management,” he said.

“No. I said, ‘I want a pill.’ She gave me something that cured it.”

Similarly, he said, most farmers want a quick and simple solution for ordinary weeds and herbicide-resistant weeds.

Integrated weed management is not a quick or easy way to cope with herbicide resistance.

That’s why it’s rarely the go-to solution for farmers.

“It (a weed) is resistant to Roundup. Can I spray a Group 2 (herbicide)? Can I spray Group 7?” Tardif said, explaining a typical producer’s reaction.

For more than 15 years, weed scientists and agronomists have tried to convinced North American farmers to employ integrated weed management, a strategy to cut the use of herbicides and reduce the risk of weeds developing resistance to herbicides.

“(It) uses a variety of control techniques to keep weeds ‘off balance,’ ” says a page on the Manitoba Agriculture website.

“Weeds are less able to adapt to a constantly changing system that uses many different control practices, unlike a program that relies on one or two weed control tools.”

There are hundreds of websites with similar information, and weed scientists have given thousands of talks about the strategy, but Tardif said few farmers are doing it.

“Awareness doesn’t mean adoption,” he said.

“I’m aware that I have to check my diet and don’t drink alcohol.”

Tardif presented a partial list of reasons why farmers don’t adopt integrated weed management:

  • too complex
  • too risky (may not work)
  • social pressures
  • too expensive

Integrated weed management asks growers to implement multiple strategies, or many little hammers, to control weeds. The choices can be overwhelming, Tardif said.

“It leads to analysis paralysis.… OK, IWM. I’ll mix it up (mix herbicides), cultivation, seeding rate, row width, fertilizer placing, timing, cultivars, cover crops. I don’t know. (It’s) so confusing. I’ll just go with a herbicide. I know it works. I’ll deal with that (IWM) stuff next year.”

Agronomic strategies, such as narrower rows, do help the crop compete with weeds and can be effective, but they’re not as effective as a herbicide and there’s still a chance that weeds could flourish.

As well, peer pressure isn’t just for teenagers.

If a neighbouring farmer sees a weedy field because cover crops and seeding rates didn’t control all of the weeds, he won’t be happy. A producer practising integrated weed management will likely hear all about his weedy field at the local coffee shop.

The biggest obstacle may be cost.

Boosting the seeding rate, incorporating cover crops and using multiple herbicides with different modes of action increases the cost of weed control.

And that leads to a cost-benefit question: why pay extra this year to prevent a problem with resistant weeds in the future?

“You can spend $20 more per acre now to save maybe $15 per acre in the future,” Tardif said.

“OK, what future? When? That becomes quite difficult (as an argument).”

Tardif proposes a different way to promote integrated weed management — pay farmers to do it.

Producers benefit by reducing the risk of resistant weeds on their farms, but he said there are also public benefits, particularly less spraying of herbicides.

“Society benefits from environmental quality … but who bears the brunt of (the cost from) integrated weed management?”

Tardif isn’t the only expert who has suggested paying farmers to encourage them to adopt the strategy.

Some Europeans have said the same thing.

“Reluctance to adopt non-chemical methods (for weed control) is not due to a lack of research or technology but to a lack of farmer motivation and action,” Stephen Moss, a British consultant, wrote in a paper published in Pest Management Science.

“If ‘persuasion’ fails to deliver greater implementation of IWM, authorities may resort to greater use of financial and other incentives, combined with tougher regulations.”

Tardif said governments may eventually crack down on farmers and tell them what to spray if herbicide resistant weeds continue to spread.

“Come with a prescription system,” he said.

“OK. What have you used last year? What’s your field history? You want to use this herbicide this year? Not gonna happen. You’re going to use that one.”

Regulation would likely be a last resort.

In the shorter term, a financial incentive might make sense, Tardif said.

Integrated weed management is an added cost for growers, and if society benefits, the public should share in the expense.

“If I’m asking you (a grower) to bear the cost of an extra $10 per acre, for 1,000 acres, that’s 10 grand,” he said.

“With all the risks linked to agriculture, that’s a big ask.”

Weeds with resistance to glyphosate in Canada

  • kochia
  • horseweed
  • giant ragweed
  • common ragweed
  • tall waterhemp
  • birdsrape mustard

Source: International Survey of Herbicide Resistant Weeds

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