The early appearance of stripe rust on crops in Oregon and Montana is a warning to Alberta growers that the fungal disease could be a problem this year.
Stripe rust spores travel easily on the wind, which means southwesterlies could bring the problem into Canada given the right conditions.
Mary Burrows, a plant pathologist from Montana State University, said in an April 4 alert that stripe rust had been found in the Flathead and Chouteau regions of Montana and that fungicide application was recommended in susceptible varieties with signs of the disease.
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In southern Alberta, winter wheat has emerged in many areas and spring wheat crops will not be far behind.
“Scout your crops,” said plant pathologist Michael Harding of the Crop Development Centre in Brooks, Alta.
No stripe rust has been reported in Alberta, but weather conditions are favourable for its development.
“This year, things are greening up, the winds are coming from the south quite a bit, or southwest, and temperatures are kind of just right in the sweet spot for stripe rust,” said Harding.
“We are just encouraging people to be on the look out for it.”
The fungal disease is easily identified by the appearance of yellow stripes parallel to the leaf veins. Spores in those stripes then rupture the leaf epidermis and are emitted as bright orange dusty material.
Harding said those who have planted winter wheat varieties without resistance to stripe rust should pay particular attention as crops develop.
Wheat can tolerate some infection without yield loss, but it depends on the degree.
“The crop will tolerate some stripe rust,” he said. “You don’t need to necessarily spray the second that you see it, but you need to be watching it very closely, and if you do see it, you need to be watching frequently.”
Fungicide should be applied in a susceptible crop once rust is seen on five percent of the leaf area.
Harding said stripe rust can move quickly, going from initial infection to spore production within a week.
“It’s kind of an explosive disease that way,” he said.
Resistant winter wheat varieties are fairly robust against stripe rust, he added. Plants may show evidence of rust at the seedling stage, but the resistance genes won’t take noticeable effect until the plant is out of that stage.
Effective fungicides are available but they are preventive, as opposed to a treatment for infection, said Harding.
The key is to scout, determine whether spraying is needed and if so, to apply fungicide at the right time.
“If you let the infection go too far, it’s really difficult to turn the corner on it,” he said.
“So yes, fungicides can be an effective tool for managing. There can be a very significant economic return, but if you get them on too late, the existing infections can’t be cured, and so you have to be ready to apply preventively.”
