Stripe rust update 06/14: Disease pressure low in Eastern Washington

By Dr. Xianming Chen

In the western Pacific Northwest (PNW), especially northwestern Washington, winter wheat ranged from kernel watery ripe (Feekes 10.54) to soft dough (Feekes 11.2) and spring wheat from stem extension (Feekes 7) to heading (Feekes 10.3). Stripe rust has been severe as normal. We completed the stripe rust data collection on winter crop nurseries and the first note-taking on spring crop nurseries in Mount Vernon, Wash., (Skagit County) on June 5. Stripe rust severity was 100 percent on susceptible varieties of winter wheat and reached 60-80 percent on susceptible varieties of spring wheat. Barley stripe rust reached 40-60 percent severity on susceptible barley varieties. Leaf rust, up to 20 percent severity, occurred on few wheat entries, but no leaf rust was found on barley, different from the severe leaf rust of barley in 2015-2017. 

In the eastern PNW, especially Eastern Washington, winter wheat ranged from heading (Feekes 10.5) to soft dough (Feekes 11.2) and spring wheat from late tillering (Feekes 4) to heading (Feekes 10.5). The pressure of stripe rust is low. In most commercial fields of winter and spring wheat fields checked this week, rust was not found, and only a few stripe rust pustules were found in a couple of winter wheat fields in Adams and Whitman counties. Stripe rust has been developing in our experimental fields around Pullman (Whitman County), Walla Walla  and Lind (Adams County), but the developing rate has been much slower than the past several years. The exception is in the wheat monitoring nurseries at the Hermiston Station in Umatilla County, Oregon. Under irrigation, stripe rust reached 100 percent severities on susceptible varieties of winter wheat and up to 60 percent severity on susceptible varieties of spring wheat. Stripe rust of barley has been found at very low levels in our experimental fields in Walla Walla and Lind. No leaf rust or stem rust has been found on either wheat or barley in the eastern PNW. 

As the crops progress, management for stripe rust on winter wheat is over. Because the stripe rust pressure is very low now and the weather has been dry in the past two weeks and is expected dry in the next two weeks or so, fungicide application on spring wheat and barley is generally not needed, except for irrigated fields grown with highly susceptible varieties. Check fields and use fungicides only when active rust pustules are quite easily found before flowering. 

Stripe Rust in the Country 

Countrywide, stripe rust has been reported relatively slow compared to the last year. Since the previous update on May 9, Kentucky and Idaho have been added to the list of states reported to have stripe rust. Thus, wheat stripe rust has occurred in Texas, Louisiana, Mississippi, Oklahoma, Kansas, Washington, California, Oregon, Tennessee, Kentucky, Idaho, Nebraska and Colorado. Except for the widespread in Texas and Kansas, stripe rust of wheat has been low in other states. Barley stripe rust has been reported in Oregon, Washington and California.