Manitoba is seeing a return of rust. Spates of rain in May and June, particularly in central Manitoba, are putting farmers on the look out for cereal leaf diseases.
Conditions have been friendly enough to disease development that David Kaminski, field crop pathologist with Manitoba Agriculture, says some growers are on their second fungicide pass.
“That early season moisture led to more people observing leaf diseases on cereals than over the last several years,” he noted.
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One of the biggest leaf diseases this year has been tan spot, primarily found on wheat.
“It’s noticed early in the year because it thrives in cool conditions. Sometimes that disease will start in the lower leaves and progress right up into the upper canopy, but often as it warms up later in the season, it stays down lower in the canopy,” said Kaminski.
Wheat is the typical victim for Septoria leaf spot, but this year it’s spread to oats as well.
Crown rust on oats, already common in Manitoba oats, is also being found.
Kaminski pointed to a number of factors behind the reports. For one, the province’s population of buckthorn shrubs along waterways give crown rust an alternate host. That can translate to a source of early season infection. The other culprit is wind blowing in crown rust spores from the U.S.
Stripe (also known as yellow) rust — which also thrives in cool temperatures — has been reported on spring wheat in Manitoba. That’s unusual, being a more typical issue in Alberta’s winter wheat acres.
Most rusts blow northward from states close to Manitoba, but an uncommon trajectory saw this stripe rust fly into south-central Manitoba from the U.S. Pacific Northwest this spring, said Kaminski. “So far, the development of that disease has not been substantial. It may have been curbed somewhat by warmer temperatures later on. But also, most of our spring wheat varieties have decent resistance to stripe rust, so that one is more of a curiosity than anything.”
Growers should approach rust control mindfully, said Kaminski “With some of the varieties that we have relied on for a number of years, there’s a resistance or tolerance that has been lost over time with all rusts. It’s a complicated life cycle, but there are sexual stages in which recombination happens. Now there’s a continual shuffling of the deck that can eventually overcome genetic resistance.”
Watch the Co-operator website and future print editions for more coverage on cereal leaf disease throughout the Prairies.
