BANFF, Alta. – Using powerful herbicides on problem weeds is like trying to kill flies with a hammer.
The hammer often misses the target and weed plagues continue.
Integrated weed management may be a more logical approach, said scientists at a recent meeting of the expert committee on weeds.
Developing a larger arsenal against weeds takes imagination, planning and initiative. Unfortunately, many farmers have not embraced the concept.
“Nobody can really tell you how to do it,” said Neil Harker, of Agriculture Canada’s research centre in Lacombe, Alta.
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“We have a long way to go.”
He said farmers and scientists need to better understand weed biology. As well, many involved in the weed battle fail to examine why there remains a perpetual presence of weeds.
Some techniques found in the integrated approach have been understood since the 1920s, when heavier seeding rates were recommended as a way to get ahead of unwanted plants in a field.
John O’Donovan, from Agriculture Canada’s Beaverlodge centre, said integrated weed management reduces input costs for farmers.
It makes weed control practices more environmentally acceptable and is not hard to do.
“It is simply good agronomy by planting high quality seed, by seeding relatively shallowly and using timely cultivation after a burn off of weeds by glyphosate,” O’Donovan said.
In various trials in Alberta, researchers have compared seeding rates and the effects on weed control. A good plant canopy blocks out weeds.
Wild oat decreases as seeding rate increases.
Researchers know that placement of fertilizer is important. Banding rather than broadcasting fertilizer gives crops a competitive edge. Wheat can outcompete green foxtail when nitrogen is banded.
Choosing the right variety of plant also has an impact.
Integrated management and barley is a good fit, but not all varieties are created equal.
Hulless and semi-dwarf varieties have good agronomic qualities, but do not compete well against weeds.
Hulless barley varieties expose the embryo, so there are germination problems.
Early crop emergence is critical to get ahead of weeds.
The later the wild oats come up after barley, the poorer the stand of weeds.
Yet farmers have not been keen to adopt the concept and do not like the idea of an acceptable level of weeds.
“Mention the word weed thresholds, and they go totally squirrelly,” O’Donovan said.
Herbicides still have a place in management programs, and 80 percent of herbicide sales are in Western Canada. However, wild oats are not disappearing in spite of chemical company claims, said Harker and O’Donovan.
Management changes may be necessary. For example, some chemicals are more effective when sprayed in the evening.
There is also a controversy over rates of application.
“The reality is many farmers are not sticking to the recommended herbicide rate,” O’Donovan said.
While chemical companies won’t take responsibility if herbicides fail after being sprayed below the correct level, research in various locations has showed that spraying at less than the recommended rate is often as effective and saves farmers
money.
In Australia, regulations were recently changed that allow farmers to apply herbicides below the recommended rate.
