Stripe rust in Central Alberta is no longer contained in winter wheat plots but has now been found in spring commercial fields, according to a plant pathologist for the province.
“It's not just a winter wheat issue anymore. It's now moved into spring cereals, kind of around that Lacombe, Olds area,” said Mike Harding, plant pathologist for Alberta Agriculture and Rural Development. “It's really critical to scout spring wheat fields now as well.”
A pair of plant pathologists for the provincial ministry, Kequan Xi and Krishan Kumar, first observed the presence of the fungal infection in winter wheat at breeding sites around Lacombe in June.
It is now imperative that farmers continue to check their fields for the disease, Harding said.
“Extremely urgent for people in that area around Lacombe, Olds, Red Deer to be scouting both winter wheat and spring wheat fields,” he said.
If stripe rust is present on susceptible crops that do not have genetic resistance, fungicide should be sprayed immediately, Harding said.
But for genetically modified wheat that's resistant to infection, fungicide is not necessary right away even if pustules are visible, he added.
“Even the varieties that have some resistance, you will still see some pustules, these orange-coloured spores that show up in strips or stripes along the leaf,” he said. “If you're growing a variety that has good genetic resistance, then you can tolerate up to 10 per cent, even 15 per cent of the leaf area affected before you consider spraying.”
According to Harding, stripe rust thrives in cool and wet conditions, often seen during June.
“That's when the spores are very successful at germinating and penetrating through the cereal leaf and starting the infection,” he said.
July brings hot and dry weather, which is not as conducive to the disease. Additionally, genetic resistance kicks in for adult plants during high temperatures, he added.
Harding said stripe rust's potential to damage yields winds down at the end of July and early August. Thus, farmers still have time to save their spring crops.
“Now is a critical time because the yield potential of the crop could still be severely harmed by stripe rust but we will reach a time eventually where it doesn't matter how much stripe rust comes in, it's not really going to affect the yield potential of the crop,” he said.
