The most popular variety of hard red winter wheat planted in Manitoba is highly susceptible to fusarium head blight, according to Anita Brule-Babel, a winter wheat breeding expert at the University of Manitoba.
Testing of the winter wheat lines at the U of M’s research centres in Winnipeg and Carman, Man., has shown that CDC Falcon is one of the most susceptible of the winter wheat lines in current use.
Although fall seeded wheat typically matures well before hot summer weather strikes, high temperatures and humidity from heavy rains sometimes arrive early enough in June, as was the case last year, to create ideal conditions for the fungus to grow.
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It is often difficult to induce fusarium infection under test conditions, Brule-Babel said, and there is some controversy among researchers over the issue, especially with regard to measurement methodology.
In field plots, even when plants are deliberately inoculated and kept under humid conditions, infection is far from an automatic result, especially when night temperatures dip below 10 C, she said.
“For producers, the earlier you get your crop in, the less likely the conditions for fusarium infection are going to be there when the crop is flowering,” she said.
“If you delay seeding, you’ll have a later heading time, and you will
also increase your risk of infection for fusarium.”
Brule-Bable said CDC Buteo seems to be showing up better in terms of resistance to fusarium infection, but some data shows that variety can be infected as well.
Brian Fowler, a research scientist at the University of Saskatchewan who was involved in the development of both varieties, said that lab results, especially with fusarium, often do not reflect field results.
“There is quite a controversy over whether you can extrapolate directly from the lab to the field,” said Fowler.
While Buteo, a CWB Select variety, is gaining popularity in Saskatchewan, Falcon is preferred in the high moisture areas of the Red River Valley.
Falcon is the shorter of the two, which leaves it more likely to become infected as raindrops splash fusarium inoculum from crop residues onto the flowering heads, he said.
Winter wheat tends to begin flowering in mid-June, which in most years gives the plant enough time to slam the infection window shut before the arrival of hot, humid weather in July.
“If it was a major problem, I would assume that there would already have been a major shift away from Falcon,” said Fowler, who added that both varieties have been around for a long time, and seed evaluation literature has long made it clear that one has greater resistance than the other.
The prevalence of fusarium in test plots can sometimes defy reason, he noted.
“I’ve had trials in Brandon where there’s fusarium and I couldn’t pick up any differences among the cultivars in the field. You tend to get areas in the plots where there’s more fusarium and areas where there’s less,” he added.
“It’s a very difficult disease to work with.”
At any rate, winter wheat is hands down the winner in terms of fusarium resistance over spring wheat, said both experts, simply because of its ability to mature earlier in the growing season.
Brule-Babel added that a harsher than usual winter can cause the fungus to emerge more slowly in spring, giving winter wheat an even greater advantage.
However, if seeding is delayed in fall, the time required for the crop to catch up in spring could push the flowering date back into the hot season, when the risk of infection is greater.
