Stripe rust, which hammered crops in southern Alberta this summer, didn’t severely limit winter wheat yields on Rod Lanier’s farm near Lethbridge. But the disease definitely cut into Lanier’s bottom line, because the grower had to spray his crop twice to restrain the fungus.
“In some of our fields, we had two applications of fungicide in order to protect the flag leaf,” said Lanier, who grew 350 acres of winter wheat in 2011.
“I did one application and it just seemed to keep coming on strong…. So we applied another product (a couple weeks later).”
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Winter wheat on one of Lanier’s fields yielded 86 bushels per acre. His other winter wheat fields weren’t as robust, but Lanier expects his average yield will be 75 bu. per acre.
Stripe rust, a virulent and highly adaptive disease, is establishing a foothold in southern Alberta.
“We have a lot of concerns about stripe rust because of its ability to change its genetic makeup,” said Denis Gaudet, Agriculture Canada plant pathologist in Lethbridge.
“Like any of the new and emerging diseases, the resistance we’re putting into (wheat) varieties may not last very long.”
A substantial portion of the disease was concentrated in southern Alberta, south of Highway 3. It also extended into other parts of Alberta and into western Saskatchewan, said Byron Puchalski, cereal pathology technician with Agriculture Canada.
Stripe rust invaded wheatfields around Calgary this summer and was also detected near Saskatoon.
“It’s kind of like a teardrop shape (centered) in southern Alberta,” he said. ” It extends north and (takes in) Swift Current and Saskatoon. It probably follows east of Saskatoon all the way into Manitoba.”
Only a few years ago, warm temperatures in the summer would hinder the development and spread of stripe rust. But a new variant of the fungus, known simply as the hot temperature strain, can withstand temperatures above 30 C.
This newer variant has likely become the dominant strain in Western Canada, Puchalski said.
Gaudet said it’s hard to quantify how much stripe rust reduced yields of winter wheat, which doesn’t have resistance to the disease, because losses will vary from farm to farm, depending on management practices. Yet, it’s safe to say that stripe rust restricted yield potential.
“The winter wheat took a pretty sizable hit,” he said.
Lanier was able to limit his yield losses by spending money and time on fungicide applications. He wants to continue growing winter wheat, but he realizes that it will require more management.
“My input costs are going to go up. I’ll have to look at more custom rates for high wheel sprayer. Or, if it gets too carried away, ( I’ll buy) a high wheeled sprayer, which isn’t where I wanted to spend money.”
Lanier may also have to manage his spring wheat more carefully, to combat stripe rust.
“It looked like it (stripe rust) was leaving the spring wheat alone,” said Lanier, an Alberta Winter Wheat Producers Commission director.
“But later near the end (of the growing season), I wished I had done more fungiciding on my spring wheat.”
Stripe rust proliferated during the wet spring in southern Alberta this year, which had the added effect of pushing back seeding dates.
“A lot of spring wheat was seeded late and it’s still fairly green,” Gaudet said. “The fungus needs green tissue to reproduce. Once the tissue is dead, it cannot grow and reproduce…. So that recreates the same conditions we had last fall, which was the creation of a green bridge.”
In the late summer and early fall, if stripe rust is still living on the green plant material in spring wheat, the disease can easily spread to newly planted winter wheat, as green shoots emerge from the soil.
That type of disease spread is known as a green bridge and is extremely worrisome because stripe rust can survive the winter in the southern Prairies if there is sufficient snow cover.
“We don’t have the (cold) winters that we need to kill off many of the species that are causing these problems,” Gaudet said.
Several spring wheat varieties, including Lillian, Harvest and Kane, possess stripe rust resistance, which means a fair chunk of the spring wheat crop weathered the rust invasion fairly well, he said.
Varieties like Superb and Barrie have less resistance, so there will be likely be yield losses in those fields.
Looking ahead to next year and beyond, Gaudet hopes growers will seek out the best information on managing stripe rust, including tips on scouting, appropriate fungicides and which spring wheat varieties have superior resistance.
Gary Stanford, an Alberta Winter Wheat Producers Commission director who farms near Magrath, Alta., said several winter wheat growers have called for advice.
“They’ve been asking me should we go get new seed? Or should we be able to clean our own seed?” he said.
“I told them make sure you (acquire) some new seed…. If your seed stock that you clean is getting older, you’ve got to get some new seed.”
