By Dr. Xianming Chen
Stripe rust is forecasted to be in the moderate epidemic level in the eastern Pacific Northwest
Based on the predication models using the weather data from November to February, wheat stripe rust is forecasted to be in the moderate epidemic level range (20-40% yield loss) in the 2022 growing season. The models predicted highly susceptible varieties to have 33% yield loss with a standard deviation of 7%. This value is similar with the 34% forecasted in January based only on the November-December weather conditions. According to this prediction, susceptible and moderately susceptible commercially grown varieties will likely have 10 to 24% yield losses, or 8% yield loss on average for commercially grown varieties.
Stripe rust has not been found in eastern Washington
So far, stripe rust has not been found in fields of eastern Washington. We checked wheat fields in Whitman, Adams, Lincoln, Grant, and Douglas counties on November 23, 2021; and Whitman, Garfield, Columbia, Walla Walla, Benton, Franklin, and Adams on March 1, 2022, but did not find any rust. Stripe rust will likely to have a late start in the eastern Pacific Northwest.
Recommendations for the eastern Pacific Northwest
As stripe rust has not been found and the disease is likely to have a late start, fungicide application is not recommended in the early growth season at the time of herbicide application for winter wheat, unless stripe rust is observed in the fields. Fungicide application may be needed later in the flag leaf stage for fields planted with moderately susceptible and susceptible varieties (stripe rust ratings 6 – 9). For spring wheat, resistant or moderately resistant varieties (stripe rust ratings 1 – 5) should be selected for planting.
Stripe rust in the country
By this time of the year, stripe rust is expected occurring in western Washington as always. So far, stripe rust has been reported only in Louisiana and Texas.