There are three strikes against Canadian prairie spring wheat varieties coming out of combines in Manitoba and eastern Saskatchewan this fall, according to scientists at Agriculture Canada.
Fusarium headblight has been cutting yields, especially for CPS varieties. And leaf spot diseases have hit all classes of wheat in the eastern Prairies.
But a Cereal Research Centre survey last month also revealed the most widespread and severe epidemic of leaf rust since 1991.
“The CPS wheats really got hammered this year …,” said Andy Tekhauz, head of the centre’s cereal disease section.
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Scientists at the Winnipeg-based centre are predicting yield losses of five to 20 percent in rusted fields.
Tekhauz said conditions were ideal for the disease, with warm nights, high humidity and morning dews.
However, he noted crown rust on oats and stem rust on barley, which thrive in these conditions, did not become a problem.
But in Saskatchewan, a plant disease specialist said he thinks excessive dryness may have limited the damage of wheat leaf rust.
Michael Celetti, of Saskatchewan Agriculture, said winter wheat growers around Nipawin first noticed leaf rust in early July.
Celetti hit the road, checking wheat fields from Regina to Melfort, and found spores in almost all of them.
But dews stayed low in the plant canopy, keeping the yield-determining top flag leaf high and dry.
Dry weather “stopped the progression of the disease, the rust, in the upper canopy, but at the same time, it was frying crops and maturing the crop much too early,” Celetti said.
In Manitoba, where 15 to 20 percent of the 3.8 million wheat acres were seeded to less-resistant CPS varieties, the effects are noticeable, pathologists said.
“There have been some newer CPS cultivars that have been developed which frankly did look a little bit better when they were tested experimentally,” Tekhauz explained.
“Now that they’re … being grown in large acreages, the resistance doesn’t seem to be adequate.”
Varieties like AC Foremost, AC Vista and AC Crystal were hardest hit, Tekhauz said. AC Karma and AC Taber have moderate resistance.
The centre’s survey also found moderate levels of leaf rust in fields of older bread wheat varieties including Roblin, Glenlea, AC Barrie and Katepwa.
Tekhauz said breeders have had a hard time in the past finding good genetic sources of leaf rust resistance to put into CPS wheats.
However, he noted better varieties should be available in the next few years.
