DISMAL returns for cereal crops have helped push Canadian farmers towards growing more oilseed crops, most of them genetically modified canola.
Canadian research scientist Hugh Beckie recently told Birchip Cropping Group members that farmers in western Canada's prairie country faced many of the same challenges as Victorian growers.
Dr Beckie said cereals would account for less than 50 per cent of their crop land in the next 10 years "for the first time in the history of agriculture".
The area under cereals had declined 30 per cent since 1976 and Canadian farmers now viewed wheat as a break crop for oilseeds and lentils, which were more profitable.
"In the past 10 years, yields of wheat and other crops have been stagnant," Dr Beckie said.
"Part of the reason is we don't have sufficient public breeding effort.
"We're falling behind countries such as Australia.
"We're in serious need of greater plant-breeding efforts, particularly in cereal crops."
Dr Beckie, an adjunct professor at the University of Alberta, in Edmonton, said Canadian farmers had completely converted from conventional canola to genetically modified and hybrid varieties since 1995.
Roundup Ready canola accounted for 48 per cent, Liberty Link 43 per cent and Clearfield about 10 per cent of last year's 6.4 million hectares.
A specialist in herbicide resistance, Dr Beckie said 46 weeds in Canada were resistant to various herbicides and some to multiple herbicides.
This has come from a reliance on Group A herbicides, which were used on almost 90 per cent of wheat and 75 per cent of barley crops.
Resistance had been found in eight of the top 10 weeds and was most common in wild oats, which growers spent $500 million a year to control.
"Growers have shied away from pre-emergent herbicides such as trifluralin, as it relies on moisture," he said.
"Farmers in Canada have mostly switched over to post-emergent herbicide use (and) we're now getting Group A and Group B resistance, similar to annual ryegrass in Australia."
Based on random field surveys, Dr Beckie estimated herbicide resistance was present in 20 per cent of Canada's cultivated land, or about five million hectares, and had doubled in the past five years to 40 per cent in the prairies.
"Besides canola, there's really no different mode of action they can use other than resorting to trifluralin, avadex and other pre-emergent actions," he said.
"It's very similar to Australia, where many growers rely on trifluralin, so we're going back to the future, so to speak.
"There's no magic bullet in terms of combating weed resistance - it's something you have to keep working at and struggle with.
``We've told growers they should rotate herbicide use by mode of action, but they're really locked into the Group A and Group B chemistries in all crops except canola.
``The challenge for industry is to get new modes of action.
``We haven't had a new mode of action in 25 years, which is astounding.''
Dr Beckie said recent research had shown mixing herbicides was more effective in delaying Group B resistance than rotating it with chemicals from other groups.
Resistance jumped from 2 per cent to 60 per cent after a single application of Group B herbicide, but no resistance emerged after four years of using a mixture of Group A and Group C herbicides.
``Crop rotation is the long-term solution, but we have to be realistic and when it's dry, some of these other crops such as canola can be risky,'' he said.
``We found if you include at least three different crop types in the rotation, such as cereals, pulses, green manure or perennial forage, you can cut the risk of resistance by up to 90 per cent.''
Dr Beckie said farmers in western Canada also were relying on GM canola as a method of managing herbicide resistance, because it offered a reprieve from using Group A and B herbicides.
He recommended that canola be grown every three or four years, but said some growers were pushing the limits with a wheat-canola rotation because of better returns from canola in recent years.
