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Can Stripe Rust Overwinter in Manitoba?

Short Answer: Yes.

Long Answer: Normally in Manitoba, the majority of our inoculum blows in from the central US states by what is known as the “Puccinia Pathway”. However, according to Dr. Brent McCallum, a Research Scientist with AAFC in Morden, MB, there was evidence of both stripe and leaf rust overwintering on winter wheat in Manitoba a few years ago but at such low levels it wasn’t a concern. Dr. Kelly Turkington, a Research Scientist with AAFC in Lacombe, AB, also indicated overwintering of stripe rust occurred in Alberta and parts of Saskatchewan in 2010/11 where there were measurable losses. In that particular year, there was a breakdown of resistance in the 2010 planted winter wheat crop and that led to higher infections into 2011.

So yes, stripe rust can overwinter. However, the ability of stripe rust to overwinter in Manitoba, or elsewhere, would depend on factors such as the severity of the winter and snowfall amounts.

If stripe rust is seen in the fall, take note of the variety and its resistance rating. Although nothing can be done about variety selection at this point, in the future consider stripe rust resistance when evaluating and selecting winter wheat varieties. Genetics….it’s a fast and easy way to protect your crop from disease pressure!

If winter weather conditions allow for overwintering of stripe rust, it could provide a local source of inoculum early in the spring – as early as the crop starts actively growing. A cool, wet spring could also favor spread and infection of stripe rust, not only to winter wheat but to other crops such as spring wheat.

If you do see stripe rust this fall in your winter wheat crop, mark those fields as ones to watch as soon as the crop breaks dormancy next spring. If stripe rust does overwinter, a fungicide application may be necessary.

Should a fall fungicide application be considered?

There has been some recent research conducted looking at the yield response and economics of a fall fungicide application in winter wheat. From 2011 to 2013, researchers from AAFC conducted a study across Western Canada looking at a variety of management factors, including one looking at a fall fungicide application. Results were recently reported in Top Crop Manager at http://www.topcropmanager.com/business-management/improving-winter-wheat-19554. The following statements are from the article.

In regards to the fall fungicide treatment, “the study showed some benefit from the fall foliar fungicide treatment, however the increase was small and resulted in decreased net returns,” says Turkington (who was involved with the study). “In areas with confirmed stripe rust in the fall, the yields gains were a bit better. However the cost of application is prohibitive at this point compared to no application. ”

More research is currently underway by Turkington and Dr. Randy Kutcher (University of Saskatchewan) looking at a fall fungicide application, a spring fungicide application at flag leaf emergence, and a dual application (one in the fall and one in the spring).  “The preliminary results after the first two years aren’t showing much of a benefit from the fall foliar fungicide application, similar to our recent study,” Turkington says. “Some of the results suggest a dual fall and spring application does not provide any additional benefit over a spring application in Western Canada.”

So for this fall, don’t pull out the sprayer if you see stripe rust in your winter wheat.  But, be ready to scout in the spring! And look for more updates to current winter wheat research underway across Western Canada.

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist and Holly Derksen, Field Crops Pathologist, Manitoba Agriculture; with assistance from Dr. Brent McCallum, AAFC Morden and Dr. Kelly Turkington, AAFC Lacombe.

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