Update of Stripe Rust and Other Wheat Diseases 5/21/09

May 21, 2009

Xianming Chen

I was checking wheat fields in eastern Washington and northeastern Oregon on May 19 and 20. Winter wheat crop in the Palouse area (Whitman County, WA) was in jointing stages ranging from Feekes 6 to 8. Stripe rust was not found even on susceptible checks in our stripe rust nurseries. In Central Ferry (Garfield County), wheat was in boot stage, stripe rust was found in a breeding nursery with one hot spot of up to 10% severity. In Walla Walla (Walla Walla County, WA), winter wheat is mostly in boot to heading stage and stripe rust was developing to about 80% severity in hotspot, but rust was not uniform in the winter nurseries. Stripe rust also showed up on spring wheat nurseries close to the hot spot in the winter nursery. In the rust nurseries at the Pendleton Station (Umatilla County, Oregon), stripe rust just started developing on susceptible entries. At the Hermiston Station (Umatilla County, Oregon), wheat was in heading to flowering stages and stripe rust was common and severe in some breeding plots with 80% severities or more in hotspots.

In the above areas, stripe rust was not found in any commercial fields checked. Near Walla Walla, a winter wheat field had quite severe physiological leaf spot. At the Hermiston Station, barley yellow dwarf was severe. Dr. Chris Mundt reported stripe rust of hot spots in an irrigated wheat field near Ione (Morrow County, OR) last week. The field was sprayed with fungicide.

In the Horse Heaven Hills area (Benton County, WA), stripe rust was generally under control. Fields found to have stripe rust a month ago were hard to find rust. The application of fungicides in this area has helped to reduce rust inoculum. I found one field with severe stripe rust. Root rot (presumably dryland root rot) was also severe in this field. As the weather has been favorable to stripe rust development and wheat crop is just up to boot stage, growers should check fields for new development of stripe rust. Fungicides generally protect plants for about one month. Growers in other areas also should start to check fields especially fields grown with susceptible cultivars.

Nationally, stripe rust has been reported in Louisiana, Texas, Arkansas, Georgia, North Carolina, California, Oregon, and Washington. Except for few locations in California, stripe rust severity has been generally low.