Stripe rust will be likely to reach a normal epidemic level in the eastern Pacific Northwest
Based on the forecast models using the weather data from November 2017 to February 2018, stripe rust will potentially cause yield loss of 17.9% on highly susceptible varieties. This number is much higher than the 6% forecasted in January based only on the November-December weather conditions. The number is an average of the prediction range from 13.8% to 23.4% using six models. Based on these prediction values, our current prediction of stripe rust is in the upper range of a low epidemic (0-20% yield loss) to the low range of a normal epidemic (20 – 40% yield loss). According to this prediction, the most “susceptible” commercially grown varieties, such as Xerpha, ORCL 102, and Eltan, will likely to have 8-12% yield losses, which still warrant fungicide application.
Stripe rust was observed in the experiment field at Walla Walla
Yesterday, I was checking wheat fields in Whitman, Lincoln, Adams, Franklin, Walla Walla, and Columbia counties. Fields in Whitman and the northern part of Lincoln were partially or entirely under snow. Wheat plants were mostly in dormancy in Whitman, Adams and the northern part of Franklin, but started growing in Walla Walla, Columbia, and the southern part of Franklin. Spotted winter injures were observed in few fields in Whitman and Lincoln. No stripe rust was observed in any commercial fields. This was different from our survey on March 8 of the last year. However, active stripe rust (Figure 1) was observed on the susceptible check variety in our experimental field at Walla Walla, similar to the last year and normal in this location.