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End Of An Era – for Jul. 29, 2010

It was dry in the late 1980s, and farmers were told by the herbicide manufacturer that’s why their favoured herbicide – trifluralin (Treflan) – wasn’t doing its job.

But two public extension workers in Manitoba, the late Ian Morrison, a weed scientist with the University of Manitoba, and Barry Todd with the soils and crops division of Manitoba Agriculture, followed up on the farmer complaints.

They confirmed the problem wasn’t because it was too dry or too hot, or too cold or too wet for that matter. It was because – after repeated use year after year – farmers had selected and multiplied resistant green foxtail populations.

After nearly two years of denial, the company, Elanco at the time, held a meeting in a rural Manitoba community hall to confirm there was a problem.

Through a combination of research and extension, Morrison, technician Lyle Friesen, students Hugh Beckie and later Ian Heap worked with provincial extension workers Todd and weed scientist Mark Goodwin to survey and quantify the rapidly evolving Group 1-and Group 2-resistant green foxtail and wild oats. Other weeds and other resistance were emerging as well.

They concluded the only way to delay onset was for farmers to rotate herbicide modes of action.

In order to simplify the decision-making process for farmers, they developed the numerical grouping system for modes of action which is still in use across North America today.

All of this was a hard sell to farmers who had not yet experienced resistant weeds. As well, these public extension workers took flak from herbicide manufacturers who didn’t like them interfering with their marketing messages.

But over the next few years, the message got through, equipping farmers in this province with the knowledge they need to stay a step ahead of weed resistance.

In fact, they are decades ahead of farmers in the southern U. S., dubbed “the glyphosate belt.” There, an already-simple rotation, often of the same crop on the ground year after year, was made even simpler when the two major crops were altered to become Roundup Ready.

Corporate agronomy encouraged farmers in that region to believe that weed control could be, and should be as simple as using one product. According to some public extension workers, they too fell prey to that thinking. The voices that warned of the eventual outcome were drowned out by those who said glyphosate resistance was never going to happen.

A decade later, the folly of that is now recognized. Glyphosate has been knocked from its pedestal as the “world’s greatest herbicide.” And weed-control researchers doubt there will be another product like it any time soon.

It’s unfortunate that history had to repeat itself, this time with a herbicide widely recognized for changing the face of agriculture by making conservation tillage a global reality.

Now that a wide spectrum of weeds has evolved to become resistant, it is commonly accepted that tillage will be making a comeback. We can only hope it will be on a smaller scale. The benefits of herbicide-tolerant crops don’t come close to the value of reduced tillage.

Adding tillage back into the equation increases costs. So does adding tank-mix partners. Last time we checked, profit margins in farming weren’t getting any wider.

The situation in the U. S. is a cautionary tale for farmers in Manitoba. It’s only a matter of time before it starts to emerge here. There are anecdotal reports of rising levels of glyphosate tolerance among common weeds in the Dakotas. It has been confirmed in giant ragweed populations in Ontario.

Even though farmers here use a more diversified crop rotation, which employs a wider range of chemistry, some of the practices here are still courting resistance.

A key concern for Lyle Friesen is the strategy of growing Roundup Ready canola on fields that have high populations of Group 1-and Group 2-resistant wild oats. The greater the population on which a farmer places selection pressure, the higher the likelihood a resistant biotype will emerge.

The past 40 years or so could well go down in history as the rise and fall of simple farming.

Technological innovations have their place in agriculture, but ultimately the success or failure of the farming system comes down to the knowledge of the farmers themselves. The trend of late has been to shift that knowledge away from the farm in the form of packaged “systems” approaches. It’s time to reverse that.

Making farm management decisions is a bit like shopping for transportation. You can expect good advice from car dealers on the relative merits of purchasing different vehicles. But they are unlikely to advise you to take the bus.

Farming isn’t simple. But some simple truisms still apply: At the end of the day, success is about making more than you spend. Diversity is key. And a strong public extension service is invaluable. [email protected]

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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