Stripe Rust Update 5/9/03

May 9, 2003

Xianming Chen

On May 8, I was checking fields for stripe rust in Whitman, Garfield, Columbia, Walla Walla, and Adams counties along Highway 26, 127, 12, 395, 260, 17, and 21. I found various levels of stripe rust in all of these counties.

Stripe rust started showing up on susceptible entries in our germplasm nurseries near Pullman. Rust incidences within the susceptible entries were less than 1%. I did not found stripe rust in commercial fields around Pullman, probably because resistant varieties are grown in the fields and the rust just starts to show up in the region.

Near Dusty, stripe rust pustules of moderately resistant to moderately susceptible reactions were found in winter wheat fields. The rust incidences were less than 1%. However, the finding shows that rust infections have already occurred in the area. Similar stripe rust situations were found in winter wheat fields in Columbia and Walla Walla counties, except that some irrigated fields in the Walla Walla County had highly susceptible reactions.

In the experimental plots at Central Ferry, some winter wheat entries had 20% of stripe rust with active spore production. Barley yellow dwarf was severe on winter wheat at this location.

From Connell to Othello, Hatton, Cunningham, and Washtucna, susceptible winter wheat fields had 100% rust incidence and 20 to 100% rust severities. Fields of yellow color could be seen from miles away. Many fields have been sprayed with fungicides. Fields not sprayed were continuing producing fresh spores.

An irrigated spring wheat field (at the tillering stage) few miles east of Othello had stripe rust on the lower leaves. Although the rust incidence was about 1%, the observation shows that stripe rust has already infected spring wheat in that area.

In Lind, stripe rust was found on susceptible entries in our germplasm nursery. In commercial fields near Lind, stripe rust pustules with resistant to moderately susceptible reactions were easily found, showing the rust has been in the region.

Powdery mildew was found on lower leaves of an irrigated wheat field near Touchet in the Walla Walla County.

Barley stripe rust has not been found in the eastern Washington because we mainly grown spring barley. However, barley stripe rust was developing in our nursery near Mt. Vernon in the northwestern Washington and also in California.

A week ago, wheat stripe rust developed over 90% severities on susceptible entries in our winter wheat nurseries near Mt. Vernon.

Because stripe rust spores are now almost everywhere in the eastern Washington and the weather conditions will be continuing favorable to the rust infection, the disease will widespread and develop on susceptible wheat varieties.

We are monitoring virulence changes of the stripe rust fungus. If you find the rust on varieties that have been previously characterized to be resistant or moderately resistant, please contact me (509-335-8086; xianming@mail.wsu.edu) or send me samples (Xianming Chen, 361 Johnson Hall, Washington State University, P. O. Box 646430, Pullman, WA 99164-6430).