Stripe Rust Update

May 5, 2005

Xianming Chen

Wheat stripe rust is widely present in the Pacific Northwest and is severely damaging susceptible winter wheat crops in the Willamette Valley, Oregon and the Horse Heaven Hill, Washington.

Yesterday, I was checking fields in Whitman, Franklin, Benton, and Adams counties. Significant stripe rust (about 20% of severity in the field and up to 60% in rust hot spots) was found in a winter wheat field about 5 miles southeast of Connell along Highway 260. Such field should be sprayed with fungicide. A field about 3 miles northeast of Connell, which did not had stripe rust when I checked two weeks ago, started showing stripe rust (less than 1%). Stripe rust was very severe in hard red winter wheat fields in the Horse Heaven Hill region south of Tri-cities, Washington. Thousands of acres grown with ‘Buchanan’, ‘Finley’, and ‘Hatton’, which were relatively uniformly infected, have been sprayed with fungicides since last weekend. Some of the fields should have been sprayed earlier. Stripe rust on lower leaves that were dried indicated that the fields were infected before the winter. Heavier rust on top of fields than lower part indicated that the initial infection was by wind-blown rust spores from the southwest direction. The severity levels of stripe rust in this region were not seen probably in the last 20 years. Crops of the Finley fields were severely damaged, which was worse than the damage on Finley crops last year in the regions near Connell. Along Highway 26, stripe rust were found in winter wheat fields, but in very low levels of resistant reaction. Stripe rust started showing up in early planted spring wheat fields. Near Dusty, a very low level of stripe rust, but with susceptible reaction was found on spring wheat plants in the early tillering stage.

Today, I was checking fields around Pullman, Colton, and Uniontown, WA, and Moscow and Genesee, Idaho. Stripe rust is developing in winter wheat nurseries. In experimental fields east of Moscow, stripe rust of up to 60% severity was on some susceptible lines. In a field of ‘Rod’ about 5 miles southeast of Genesee, stripe rust was uniformly distributed in the field, with low severity and generally resistant reactions. Several other fields with the similar situation were found in this region. In a field of ‘Tubbs’, about 3 miles east of Uniontown, stripe rust was not found. Stripe rust were not found in many winter wheat fields from Genesee to Uniontown and along Highway 195.

According to Jim Peterson, fields of ‘Foote’ in the Willamette Valley had a significant level of stripe rust severity as early as February, and have been sprayed with fungicides twice. He also reported stripe rust of up to 60% severity on ‘ORCF-102’ in an email. Wheat cultivars ‘ORCF-101’, “Tubbs’, ‘Weatherford’, ‘Stephens’, ‘Madsen’, ‘ID587’, and ‘OR9801757’ were not affected.

The current weather conditions are very favorable for stripe rust infection and spreading and the weather conditions will continue to be favorable in the next couple of weeks. Check your fields for stripe rust and spray fungicide in a timely manner to avoid major damage.