By Dr. Xianming Chen
Based on the predication models using the weather data from November to February, wheat stripe rust is forecast to be in the moderate epidemic level range (20-40 percent yield loss) in the 2022 growing season. The models predict highly susceptible varieties to have 33 percent yield loss with a standard deviation of 7 percent. This value is similar with the 34 percent forecast 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 percent yield losses, or 8 percent yield loss on average for commercially grown varieties.
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 Nov. 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 have a late start in 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.
By this time of the year, stripe rust is expected to be occurring in western Washington. So far, stripe rust has been reported only in Louisiana and Texas.