February 18, 2011
Stripe rust of wheat has waked up much earlier this year than last year in the Pacific Northwest and may not have slept in the western Oregon and western Washington. Don Wysocki and Jim Towne found sporulating rust pustules in a wheat field near Pendleton in the northeastern Oregon on the 1st of this month. Last week, Mike Flowers and Chris Mundt reported that stripe rust was easily found (about 5% incidence) in wheat fields in the Willamette Valley of western Oregon.
Yesterday, I stopped by the Horse Heaven Hills in the south-central Washington and found sporulating rust pustules in several wheat fields, even in some fields where plants were still small (5 to 7 leaves without dead leaves) and stripe rust was not found in last November. Rust severity was up to 5% of incidence. The rust has survived the relatively mild winter with help with the widespread snow cover in the cold spell of the first week of last December.
Rust will develop fast when weather gets warm (night temperatures into the 40s F and day temperatures into the 50s F). Considering widespread infection before the winter, early application of fungicides will be better for fields planted with susceptible and moderate susceptible cultivars. Please check your fields when weather in your area reaches the above range and if you see stripe rust, consider spaying with fungicide even before herbicide application. If no rust is found but the planted cultivar is susceptible or moderately susceptible based on last year’s reaction, the field should be sprayed with fungicide when you spray herbicide. Please consider using full rate of fungicide at the time of herbicide application as the rust has already started so early and this rust season will likely be very long.