Everything changed for agriculture after the Second World War.
As the world went to war, the sector was largely driven by horsepower. By war’s end, it was poised for rapid mechanization and the Green Revolution. which brought about increased use of fertilizer and herbicides, all products of wartime research efforts.
The widespread use of nitrogen fertilizer, for example, came when chemical firms sought a new use for their explosives plants.
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The ubiquitous 2,4-D herbicide became commercially available in 1945. It and the similar 2,4,5-T and MCPA were developed under top secrecy, independently, by four research groups in the U.K. and U.S.
As producers adopted these new tools, they also adopted the attitude and language of war. They did battle against weeds. They fought back against fungus. They defeated insects. They were, in essence, in a pitched battle against Nature.
For decades they largely won that battle. Yields jumped, harmful pests were managed and a Golden Age for farms emerged. Farmers were, for the most part, able to spray their way out of anything but weather problems.
Then challenges began to emerge in the form of herbicide-resistant weeds, brought to the forefront through selection pressure. Essentially the same product, applied over the course of many seasons, selected for the very small proportion of weeds that were naturally unsusceptible to the control method being applied.
It would have looked something like this: a farmer sprays an infested field and kills a million of the weeds in question. One survives. To the farmer of 1948, that would have looked like a miracle. But by 1988, when that farmer’s kid was running the place, that resistant population had become the general population of that weed. The miracle didn’t work anymore.
I choose 1988 because that’s when Group 2-resistant kochia and Group 3 resistant green foxtail were first identified in Manitoba.
Canada now ranks No. 3 in the world for herbicide resistant weeds. There are about 75 unique species, according to federal research scientist Charles Geddes, as reported by our sister publication Alberta Farm Express last summer.
Manitoba is at the top of the list on the Prairies with 30 resistant weed species, compared to Alberta’s 24 and Saskatchewan’s 22. Nationally, Ontario is in the lead, if you can call it that, with 38 resistant weed species.
Digging deeper into the Manitoba situation, the 2016 provincial weed survey (the most recently completed) showed that 68 per cent of surveyed fields had Group 1 and-or Group 2 resistant weeds. A total of 14 species with known herbicide resistance were identified. Since then, that number has grown, and the ongoing weed survey conducted this summer will undoubtedly find expanded resistance when its results are released.
New chemistry won’t solve this evolving problem. As one scientific paper from the website Science Direct recently noted, until the 1990s a new mode of action was introduced, on average, once every three years. But as of the 2021 publication of the article, no novel mode of action had been introduced since 1992. The low-hanging fruit of chemistry has been plucked.
This means the solution to this thorny problem is likely to be complex. As Don Norman reports for our Nov. 17 issue of the Co-operator, integrated weed management is the key.
If herbicides were one big sledgehammer, other tools are more like a bunch of small hammers, chipping away at the problem. That can be effective, but it’s going to require changes to the way things are now done.
It may mean changing the crop mix, since planting the same handful of spring annual crops provides a stable basis for weeds. Perennial crops, cover crops or winter cereals may be required.
It may mean higher seeding rates to let crops close the canopy just that little bit faster, choking out weeds.
It may mean capturing and destroying — either mechanically or through composting or fire — weed seeds during harvest.
It may mean mechanical destruction like tillage, with that tillage done in the coming years by small autonomous robots, once the sensors and weed identification database become robust.
It will likely mean all these things, in some combination, to suit an individual farm.
What are you doing to prepare your farm for that future?
