Stripe Rust Update 7/2/08

July 2, 2008

Xianming Chen

Stripe rust has still taken a slow pace for developing in the Pacific Northwest due to the low temperatures before mid June and the recent dry and hot weather conditions. Winter wheat reached soft dough to maturing stages in the south-central Washington and northeastern Oregon and flowering to milk stages in the Palouse regions of eastern Washington and northern Idaho. Spring wheat and barley crops reached boot to flowering stages.

On June 25, stripe rust was about 30% severity in average on susceptible spreader rows in breeding nurseries near Moscow, Idaho with few hot spots of 70% severity. Stripe rust was found on joint goat grasses in a winter wheat field north of Moscow, but no rust was on wheat plants. No rust was found on winter crops in all checked commercial winter wheat fields in the Palouse area. Rust infections of less than 1% were found in a couple of commercial spring wheat fields near Oaksdale and Farmington, Washington, but plants had resistant reaction. Similar reactions and infection levels were found in spring wheat experimental plots near Colfax, Washington. John Moffatt reported hot spots of stripe rust on winter wheat in his breeding nurseries about 3 miles southwest of Colfax.

Bradford Brown found stripe rust on winter wheat in Parma, Idaho, southwestern Idaho.

On June 30, stripe rust reached 40% severity in average on susceptible winter wheat entries, but still not uniform in our experimental fields near Pullman, WA, and 10% severity in spring wheat nurseries. Stripe rust was about 5% on susceptible spring barley entries.

On July 1, 80% of stripe rust was observed on highly susceptible winter wheat entries in our experimental fields in Walla Walla, WA. Susceptible spring wheat entries had up to 30% severity. Trace stripe rust was found on susceptible barley entries. In Pendleton and Hermiston, OR, stripe rust reached to 20% severity on susceptible spring wheat entries.

Near Corvallis, OR, up to 60% stripe rust was observed on susceptible entries in an experimental field.