Stripe rust update 04/16: Pressure low in PNW

From Dr. Xianming Chen

On April 13 and 14, we were planting spring cereal nurseries and taking the first notes of the winter nurseries at Mount Vernon on the west side of Washington state. The winter plants were at jointing stage ranging from Feekes 4 to 6. Wheat stripe rust was up to 40 percent severity on susceptible varieties. Barley stripe rust was also observed on susceptible varieties at relatively low incidence and severity compared with stripe rust on wheat. Although rust was not uniform yet on susceptible varieties, the severity level was relatively normal for this location at this time of year.

Stripe rust in winter wheat nurseries at Walla Walla, WA on April 15, 2021.

On April 15, we were checking winter wheat fields in the Horse Heaven Hills area in Benton County, Walla Walla County and Columbia County on  the east side of Washington state. Winter wheat ranged from Feekes 3 to 6.  No rust was found in any commercial fields.  Stripe rust was found on a susceptible check variety at several spots, but mainly at the low leaves in our stripe rust monitoring and screening nurseries near Walla Walla. At this location, stripe rust was observed at a similar level on Feb. 26 of last year, and similar levels of stripe rust are normally seen in the first or second week of March.  We did not find any rust in our previous check of this nursery site on March 9 of this year. So, stripe rust in Walla Walla started more than one month later than normal and about seven weeks later than the last year.

Stripe rust has not been reported in Oregon and Idaho. When checking our monitoring nurseries at Hermiston, Ore., yesterday, we did not find any rust.

As stripe rust was forecasted low and the pressure is currently low in the Pacific Northwest, fungicide application is not recommended in the early growth season for winter wheat on the east side, unless stripe rust is observed in fields.

Stripe rust in the country 

In addition to Washington state, wheat stripe rust has been reported so far in Louisiana, Texas and Oklahoma.  The disease may spread further north in the Great Plains and to the eastern states.