By Dr. Xianming Chen
During our field survey on July 9 in Whitman, Garfield, Columbia, Walla Walla and Astotin counties of Washington and Nez Perce and Latah counties of Idaho, winter wheat ranged from milk to mature. Stripe rust was found on green plants in some winter wheat fields, but at very low levels. Spring wheat ranged from heading to milk stages, and stripe rust was hard to find in most of the fields checked. In two fields of Genesee (Latah County), Idaho, leaves with single stripes of rust were relatively easy to found, but the incidents were still below 1 percent. No stripe rust was found in checked commercial spring barley fields. Except for late planted fields in high elevations, the stripe rust season is basically over.
Stripe rust in the country
Since the previous update on June 14, stripe rust has been reported in Minnesota, South Dakota and Michigan. Thus, wheat stripe rust has occurred in following 16 states: Texas, Louisiana, Mississippi, Oklahoma, Kansas, Washington, California, Oregon, Tennessee, Kentucky, Idaho, Nebraska, Colorado, Minnesota, South Dakota and Michigan. Barley stripe rust has been reported in Oregon, Washington, and California.
Other rusts in the Pacific Northwest
We completed rust data collection in our winter and spring nurseries of both wheat and barley at Mount Vernon (Skagit Co.) in northwestern Washington on June 26. Both stripe rusts of wheat and barley were as severe as in past years. Up to 40 percent severity of leaf rust occurred on few winter wheat germplasm lines. No barley leaf rust was found, which was very different from severe leaf rust situations in the same location in 2015 to 2017.
In eastern Pacific Northwest, wheat leaf rust was found in winter wheat nurseries in Central Ferry (Garfield Co.) and in spring wheat nurseries in Walla Walla, Wash., but not found in checked commercial fields in Washington and Idaho during our survey on July 9. No barley leaf rust was found or reported. Barley leaf rust appeared only once in eastern Pacific Northwest in 2017.
Stem rust was found in winter wheat nurseries in both Pullman (Whitman Co.) and Central Ferry (Garfield Co.). In our experimental field near Pullman, two separate spots of stem rust occurred on a single cultivar (Rosalyn). Each spot had 3 to 5 stems and leaves rusted. In the Central Ferry field, stem rust pustules were found on one or two stems or leaves.