Stripe rust overwintering on three winter wheat fields in the Edmonton area is “concerning,” says a provincial winter wheat agronomist.
“Last year, stripe rust overwintered in the central Alberta region, near Lacombe, Red Deer, and Olds, which was alarming because it really hasn’t overwintered in years,” said Janine Paly of Ducks Unlimited Canada.
“Last year, there was early-onset stripe rust in the Edmonton region, but this year is the first year that we’ve seen stripe rust overwinter in the Edmonton region.”
And the disease seems to be spreading north, she said. Last summer, a late infection of stripe rust was found in Beaverlodge — “the first year it was found in the Peace region.”
“We have seen stripe rust in the past come up as far north as the Barrhead region, but this is really the first time we’re seeing stripe rust overwinter this far north.”
So far this year, Alberta Agriculture and Rural Development has confirmed that stripe rust has been found in four counties in southern Alberta, and in mid-April, Alberta Agriculture researchers found stripe rust at a winter wheat plot in Olds.
“The snow had just melted and the field was still wet, and we found one per cent up to 10 per cent stripe rust in some places,” said research scientist Krishan Kumar.
“On susceptible varieties, this is a concern. If the weather is good and there’s a lot of moisture, it will keep on multiplying in the field.”
But the disease isn’t limited to research plots in Olds, he said. “We’re getting quite a few reports of stripe rust, especially in the central Alberta area.”
Overwintering in stripe rust is generally caused by spores moving from spring wheat still in the field to winter wheat that’s just becoming established, said Kumar.
“This crop was planted in September or October of 2014, and at that time, there was still some spring crop in the field,” he said. “The stripe rust transferred from the spring crop to the winter crop, and the snow fell and worked as insulation for its survival there.”
But central Alberta’s relatively mild winter should have worked against the disease, said Paly.
“I didn’t think it would overwinter in the Edmonton region, given that the snow came later in the year and we had a fluctuation in temperatures, exposing the spores to cooler temperatures,” she said.
“This has caught me off guard for sure.”
Stripe rust is “getting to be more common,” said Kumar, and can cause a lot of damage “depending on when it comes and how severe it is in the field.”
And because the disease is already popping up around the province, producers shouldn’t wait to start scouting their winter wheat fields, said Paly.
“Producers need to be aware that if they have winter wheat in central Alberta or even in the Peace, they should be out monitoring their fields,” she said.
“If I’m finding stripe rust now, they should be out monitoring their fields right now as well.”
At this point, producers should be monitoring their fields every three to five days, said Paly.
“If it stays on the lower leaves and the weather conditions aren’t favourable for the development of stripe rust, then we should be OK. They may just have to spray later on, at head emergence,” she said, adding that the disease fares best in cool, wet environments.
If, however, the disease starts moving up through the canopy, “that’s cause for concern.”
“That’s when the growers should be monitoring their fields quite regularly to make sure the disease doesn’t spread to the upper canopy.”
Producers growing a susceptible variety of winter wheat should spray “around stem elongation and come back later at the anthesis timing” to reduce the spread, but if the variety has some disease resistance, producers simply need to monitor their fields.
“If the disease is developing severely, they may want to think about using a fungicide to protect the plants, but if they have a resistant variety, the stripe rust shouldn’t develop any further.”