Xianming Chen
Stripe rust has started developing in the eastern Pacific Northwest
Yesterday, we were checking winter wheat fields in Whitman, Garfield, Columbia, Walla Walla, Franklin, and Adams counties in Washington. Because of the high moisture, wheat crops look good with winter wheat ranging from early jointing (Feekes 5) to boot (Feekes 10) and spring wheat ranging from just emerged to late tillering (Feekes 3). Stripe rust was found at very low level in our experimental fields near Pullman (artificially inoculated) in the Palouse region (Figure 1), Central Ferry (not inoculated, but rust might be from the inoculated breeding nursery) in Garfield County (Figure 2), and Walla Walla (natural infection, Figure 3). The low level of stripe rust in Walla Walla is about one month later than the last year and more than two months later than normal. For commercial fields, stripe rust was found in only two fields in Walla Walla County between Weitsburg and Walla Walla (Figure 4). Although the incidences were very low, the observed rust pustules were active, producing new spores.
Figure 1. Wheat stripe rust in an artificially inoculated winter wheat nursery near Pullman (Whitman Co.) WA on May 11, 2022
Figure 2. Stripe rust in a winter wheat nursery at Central Ferry (Garfield Co.), WA on May 11, 2022
Figure 3. Stripe rust in a winter wheat nursery in Walla Walla (Walla Walla Co.), WA on May 11, 2022
Figure 4. Stripe rust in a commercial winter wheat field between Waitsburg and Walla Walla (Walla Walla Co.), WA on May 11, 2022
According to several scientists, stripe rust was found in Gilliam and Morrow counties in north-central Oregon in the last week.
Although the current pressure is low, stripe rust is expected to develop in the eastern Pacific Northwest in the next few weeks because of the vigorously growing crops and the rust-favorable weather conditions in the past weeks and forecast for the next couple of weeks. Fungicide application is recommended for fields planted with susceptible and moderately susceptible varieties of winter wheat (stripe rust ratings 6-9) before flowering stage. It is good to check fields planted with moderately resistant varieties (stripe rust ratings 4 and 5). Growers should check fields immediately in south-central and central Washington, Oregon, and southern and central Idaho for stripe rust. Fields in the Palouse region of Washington and Idaho and further north should be checked starting about 10 days from now. For trying to use one application to keep rust under control, fungicide application can be done when rust incidence or severity is between 1 to 5%, not later than 10%. For spring wheat, fungicide application is recommended for fields planted with susceptible and moderately susceptible varieties (stripe rust ratings 6-9) at the herbicide application time.
Stripe rust in the country
So far, stripe rust has been reported on wheat in Louisiana, Texas, Washington, Oregon, Georgia, and California and on triticale in California; and barley stripe rust has been reported in Washington and California. Due to drought conditions, stripe rust has not been found in central Great Plains like Kansas.