WAWG
By Dr. Xianming Chen
USDA-ARS Research Plant Pathologist
Wheat stripe rust is forecasted to be in the upper range of severe epidemic (40-60% yield losses on susceptible varieties) in the 2026 growing season for the eastern Pacific Northwest, based on the predication models using the weather data from November 2025 to February 2026. The models predict highly susceptible varieties to have 55.8% yield loss with a standard deviation of 6.2%. This value is like the 56.7% yield loss forecasted in January based only on the November-December weather data. According to these predictions, commercially grown varieties will likely have up to 40% yield losses, or 8% yield loss on average for commercially grown varieties without fungicide application.
Stripe rust is widespread, and the pathogen is actively producing spores in central Washington
On March 3, we were checking winter wheat fields in Whitman, Lincoln, Adams, Franklin, and Walla Walla counties and found stripe rust in all these counties except Whitman (including our experimental fields near Pullman). Rust incidence and severity were more in the south than the north, correlating to the temperature patterns. In Lincoln County, we found stripe rust in 7 out of 10 commercial fields. Most of rust pustules were in the dormant stage with few active pustules. In Adams and Franklin counties, active stripe rust pustules producing spores were found in every checked field (8 or 9 fields checked in each county). In our experimental field at the Lind Station in Adams County, stripe rust reached 50% incidence. Stripe rust was more severe in our experimental field in Walla Walla, with incidence over 80% and rust reaching top leaves. This is the most widespread and severe stripe rust by this time of year in Washington since 2011.
Recommendations for managing stripe rust in the eastern Pacific Northwest
The field observations show the unusually early development of stripe rust, and the predictions indicate high potential yield losses in the 2026 wheat crop season for the eastern Pacific Northwest. Fungicide application is recommended for the winter wheat fields planted with moderately resistant to susceptible varieties with stripe rust ratings 3 to 9 at the time of herbicide application, and a second application may be needed 20 to 30 days after the first application, which can be determined by whether active stripe rust appears in the field after the first application. As many resistant varieties (stripe rust ratings 1 and 2) have only high-temperature adult-plant (HTAP) resistance, which will not be effective until the weather gets warm and plants reach the middle jointing stage (Feekes 7), stripe rust can develop on these varieties. Therefore, any wheat fields should be checked for stripe rust. If active rust is found, fungicide should be applied at the timing of herbicide application. Refer to my previous report “2026 First Stripe Rust Forecast for the Eastern Pacific Northwest” for stripe rust ratings of wheat varieties.
For spring wheat, resistant varieties (stripe rust ratings 1 or 2) should be selected for planting. If for any reason varieties in the other categories (stripe rust ratings 3 to 9) are going to be planted, fungicide application will be likely needed at the time of herbicide application. To select fungicides, please refer to the Appendix Table at the bottom of this post for information on active ingredients, application rate, control effect, effective duration, total limit per crop, and stage or date of application restriction.
Stripe rust in the country
In 2026, stripe rust was first reported in central Washington on Jan. 15, Pendleton, Ore., (Umatilla County), on Jan.27, Davis, Calif., (Yolo County) on Feb. 9, and Hill and McLennan counties in Texas on Jan. 12. The observations of stripe rust in the Davis area of California were also unusually earlier than normal. The occurrence of stripe rust in Texas in January is an indication of severe epidemic in the southern Great Plains and potentially epidemics in the central and northern parts of the Great Plains.