By Jennifer Blair, Alberta Farmer Express
Winter wheat producers in southern Alberta should be safe from stripe rust for another year, says a research scientist at Agriculture and Agri-Food Canada.
“We surveyed and we didn’t find any stripe rust at all,” said Denis Gaudet. “That takes off a huge weight from the standpoint of we don’t have to worry about an overwintering event this winter.”
The dry summer was key, he said, as stripe rust’s airborne spores only develop on living plants, and spring wheat ripened before the winter wheat was established.
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“An important phase of that overwintering and the disease cycle is actually going from the green spring wheat to the green winter wheat that’s emerging in the fall,” he said. “If there’s quite an overlap between those two phases, you get what we refer to as a ‘green bridge.’ That’s where you can get epidemic development in the winter wheat and in the spring wheat.”
Stripe rust is becoming a bigger problem in southern Alberta, with spores blowing in from the U.S. Pacific Northwest. During mild winters, stripe rust can spread to fields in central Alberta as well, causing overwintering events that can devastate yields.
“Stripe rust can cause heavy, heavy losses in winter wheat, up to 40 or 50 per cent losses,” said Gaudet. “In spring wheat, we expect the same losses depending on whether there’s an overwintering event.”
Improved genetics and resistant varieties, particularly in spring wheat, have helped and should reduce the need for costly fungicides, he said.
“There’s good resistance out there, so there’s no reason to be spraying. Just select varieties that are resistant, and you don’t have to worry about it.”
Regular field scouting is also critical. Stripe rust typically presents as long pustule stripes on leaves that, as they erupt, cause leaves to shrivel.
“Producers should be looking for the rust pustules on the leaves,” said Gaudet. “If it’s not there and it’s not going to develop, then there’s no use in spending a lot of money on fungicides. It really is a situation where a producer should be out monitoring his crop before he applies it.”
Producers should also prevent the “green bridge” by not seeding winter wheat too early. Gaudet recommends spraying as a “last resort,” only to be used if the stripe rust pustules appear early in the growing season.
“If it’s moving in past flowering, for example, it’s very unlikely that it will have an impact on yield,” he said.
As new resistant varieties are developed for both winter and spring wheats, producers will have little need to worry about the disease, but Gaudet encourages them to keep a careful eye on their crops until then. “We’re hoping we’re going to have this in check in the future, and hopefully, there will be a reduced need for fungicide control,” he said. “But for the time being, it still remains a threat, so we should be vigilant about it.”
