Stripe Rust in the Pacific Northwest
During the last two weeks, we have been recording stripe rust data in our experimental nurseries at various locations, and completed note-taking of winter nurseries at all locations. Stripe rust reached 90 to 100% severity on susceptible winter wheat varieties at all locations (Figure 1). Barley stripe rust developed up to 80% severity at Mount Vernon in western Washington, but relatively low compared to wheat stripe rust at locations in eastern Washington. By this week, winter wheat reached maturity in central Washington and the Walla Walla area, but still green in the Palouse region. Lodge is common in winter wheat fields in the Walla Walla area (Figure 2).
Stripe rust is under control in commercial winter wheat fields. Only few fields were observed with inactive stripe rust due to fungicide application. As winter wheat has approached and is approaching maturity in Pacific Northwest, stripe rust management is over for winter crops.
Spring wheat and spring barley range from boot (Feekes 10) to milk stage (Feekes10.54) depending upon region and planting date. Wheat stripe rust reached 80 to 100% severity on susceptible spring wheat varieties in Walla Walla and Lind and up to 60% severity around Pullman in our experimental fields (Figure 3). As the weather conditions are still favorable for stripe rust, the disease can still develop over the next two weeks. In spring wheat fields grown with moderately susceptible and susceptible varieties (stripe rust ratings 5 – 9 on the Seed Buying Guide), fungicide application is needed. If sprayed, please check fields about three weeks after the application and apply fungicide again if active stripe rust pustules are easily observed. For spring barley, fungicide application is not necessary as barley stripe rust inoculum is much lower than wheat stripe rust, but if rust severity reaches 10% incidence, consider fungicide application.
Figure 1. Severe stripe rust on a susceptible winter wheat variety in an experimental field near Pullman, WA (June 24, 2020)
Figure 2. Lodge in a winter wheat field near Walla Walla (Walla Walla County), Washington (June 30, 2020).
Figure 3. Stripe rust on a susceptible spring wheat variety in an experimental field near Pullman, WA (June 25, 2020)
Other Rusts in the Pacific Northwest
Wheat leaf rust and barley leaf rust, which occurred frequently in Mount Vernon (Skagit County) in the past, are absent in our experimental fields there this year. Only one leaf of a winter wheat with leaf rust pustules was observed when we were taking stripe rust notes last week in our experiment field near Pullman (Whitman County). Small leaf rust pustules were observed yesterday on few leaves of a winter barley variety in a winter wheat breeding nursery in Central Ferry, WA (Garfield County).
Mike Pumphrey observed stem rust on a winter wheat variety (‘Norwest Tandem’) in an experimental nursery near Pullman on June 29 (Figure 4).
Figure 4. Stem rust observed on a winter wheat variety in an experimental field near Pullman, WA on June 29 (picture from Mike Pumphrey).
Stripe Rust in the Country
So far, wheat stripe rust has been reported in Oregon, Washington, Texas, Louisiana, Oklahoma, California, Kansas, Kentucky, Virginia, Illinois, Idaho, New York, Wisconsin, Nebraska, South Dakota, and Minnesota. Barley stripe rust has been reported in California, Oregon, and Washington.