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Stripe Rust Update March 19, 2026

Xianming Chen


A. Stripe rust is developing in the Pacific Northwest



On March 18, we were checking wheat fields in Franklin, Benton, Walla Walla, Columbia, Garfield, and Whitman counties. Wheat plants ranged from Feekes 3 to 6. Stripe rust was found in all counties. In Franklin County, stripe rust has developed quickly since the field check on March 3, forming rust foci (hot spots) of several feet in diameter (Figure 1).



Plants with orange spores exhibiting necrosis on their leaves

Figure 1. Stripe rust foci in a commercial wheat field in Franklin County, WA on March 18, 2026.

 




 


In Horse Heaven Hills (Benton County), rust incidence was much higher, reaching 40% incidence. Most of infections were still on low leaves but producing large quantity of rust spores (Figure 2).



100% of the leaves on this wheat are covered in rust spores

Figure 2. Stripe rust fungus heavily infected low leaves of wheat plants and producing large quantity of spores in a commercial wheat field in Horse Heaven Hills (Benton County, WA) on March 18, 2026.

 




 


In Walla Walla, Columbia, and Garfield counties, stripe rust incidence and severity levels were much low in commercial fields (Figures 3 and 4) compared to Benton and Franklin counties, and almost all observed infections were on middle and top leaves, indicating recent infections. However, the disease was severe on susceptible varieties in our experimental field in Central Ferry (Garfield County), where wheat plants reached Feekes 6 and rust were over 90% incidence, 80% severity on low to middle leaves, and reached 40% incidence and severity on top leaves (Figure 5).



Rust spores on wheat leaves with no necrosis
Figure 3. Stripe rust observed in a commercial wheat field in Walla Walla County, WA on March 13, 2026.

 





A tip of a wheat leaf with rust spores and no necrosis


Figure 4. Stripe rust in an experimental wheat field in Columbia County, WA on March 18, 2026.

 





Tips of the wheat leaves are covered in spores
Figure 5. Stripe rust in an experimental wheat field in Central Ferry (Garfield County, WA) on March 18, 2026.

 




 


In Whitman County, stripe rust was first reported on cultivar ‘Nova AX’ in the Penawawa area in the southwest corner of the county on March 6 by Morgan Menaker, Regional Extension Agronomist, Washington State University. Yesterday, we found stripe rust in our experimental fields on the Palouse Conservation Field Station near Pullman (Figure 6). The rust incidence was low, and infections were on the first leaves, indicating that infections occurred before the winter. The observation of stripe rust at this location was about 5 weeks earlier than normal and 3 weeks later than the detection in 2011.



Many plants covered in orange spores showing severe infection rates
Figure 6. Stripe rust observed in an experimental field near Pullman (Whitman County, WA) on March 18, 2026

 




 

According to Dr. Ray Qin, stripe rust has been found in our stripe rust monitoring nursery at the Oregon State University Hermiston Agriculture Research and Extension Center (Umatilla County, OR).


Recommendations for control of stripe rust are the same as the previous. Please refer to “Stripe Rust Forecast and Update, March 4, 2026” for detail. Generally, please start checking your fields and use fungicides at the time of herbicide application, if you see rust.

 

 B. Stripe rust in the country



Since March 4, 2026, there have been no new states with reported stripe rust. So far, stripe rust has been reported in Washington, Oregon, California, and Texas.