Preventing resistance relies on sharing research info

Advice on herbicide use is becoming increasingly complicated and confusing, and farmers are well within their rights to ask tough questions about which products might best serve their needs.

The complexity is growing because herbicide resistance among weeds is in-creasing, even as new solutions are not forthcoming. Confusion is also starting to take hold because information can often be delivered in snapshots instead of in big picture format.

Herbicide use remains crucial; it is perhaps the most crucial tool in crop management.

Agriculture Canada’s Bob Blackshaw of the Lethbridge research centre recently undertook a study on where input costs could best be reduced. He provided some suggestions, but he advised never to cut back on herbicide because weeds affect yields so significantly.

Given its enormous value, how do you keep a herbicide from losing its effectiveness? Hugh Beckie, a researcher with Agriculture Canada, said tools at the disposal of prairie farmers are limited.

“I do firmly believe that weed resistance is the biggest threat to sustainable agriculture, just because the pipeline of new herbicide modes of actions are empty,” he said at the Agri-Trend 2012 Farm Forum Event Nov. 30.

Several examples of the changing resistance landscape have emerged lately. For instance, the emergence of glyphosate-resistant kochia in southern Alberta and Saskatchewan has raised the question of how to get rid of it.

Blackshaw has said that kochia cannot be killed with the Group 4 herbicide 2,4-D, although dicamba still appears to be effective. However, he said increasingly higher dicamba concentrations will probably be necessary to control the weed, which raises the question of how long it will be effective.

In addition, Alberta has 20 herbicide-resistant biotypes, Saskatchewan has 18 and Manitoba 21. The most troublesome for producers are Canada fleabane or horseweed, wild oat, barnyard grass, lamb’s quarters and redroot pigweed.

Some scientists say glyphosate in particular has been overused, while others still recommend it to control volunteer weeds. There is good advice within specific areas, but the big picture remains elusive.

It’s still a bit of a new world for western farmers because the first glyphosate-resistant weed in Western Canada was confirmed in late 2011, although basic agronomic theory still applies.

Growing multiple crops in rotation and rotating through herbicide groups with different modes of action are the first line of defence in avoiding weed resistance problems. Seeding rates and fertility programs also have an impact on weed growth. Keeping equipment clean prevents the spread of weeds, including resistant types.

However, farmers will need more information in an increasingly herbicide-resistant environment. Farmers and weed control companies must think long-term, while keeping an eye on future profitability.

Overusing cheap herbicides and pushing rotations may generate higher income today but destroy the usefulness of the herbicide in the future. Also, land overrun with herbicide-resistant weeds will become less valuable.

Farm groups are realizing there is a pressing need to get the results of re-search and recommendations on best management practices to growers and are emphasizing that in newsletters and other forms of communications.

More funding for education, based on research and provided by independent sources, would be helpful in making recommendations on the best agronomic practices.

More profitable and more sustainable farming practices can peacefully co-exist if farmers are shown the way.

Bruce Dyck, Terry Fries, Barb Glen, D’Arce McMillan and Joanne Paulson collaborate in the writing of Western Producer editorials.

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