WSU Forecast Predicts Quiet Year For Stripe Rust

According to the latest forecast released by Washington State University, stripe rust is forecasted in the low epidemic range for the eastern Pacific Northwest.  Low epidemic range, meaning a 1%-20% yield loss, is anticipated for the 2025 growing season, based on the predication models using the weather data from November 2024 to February 2025.  WSU’s models predicted highly susceptible varieties to have 18% yield loss with a standard deviation of 9%.  This value is much lower than the 41% forecasted in January based only on the November-December weather data.  The reduced predicted yield loss was due to the cold weather in February.

According to the current prediction, commercially grown varieties with moderate (5), moderately susceptible (6, 7), and susceptible (8, 9) stripe rust ratings will likely have 2 to 13% yield losses, or 2.4% yield loss on average for all recently grown winter wheat varieties without fungicide application.  For comparison, the last March forecast was 51% yield loss for highly susceptible varieties, and the susceptible check had 56% yield loss in the winter wheat experimental field in 2024.

Of Tuesday March 4th, stripe rust has not been found in central Washington fields.  WSU added wheat plants in Whitman, Adams, Lincoln, Franklin, and Walla Walla counties were generally in good condition without obvious winter injury.  WSU said no stripe rust was observed in any of the checked fields, including the commercial wheat field east of Almira along Highway 2 in Lincoln County, the same field where we found stripe rust on November 5th, 2024.   In the last year, stripe rust was found in several fields by the end of February.

What are the recommendations for growers in the eastern portion of the Pacific Northwest?  Based on the currently predicted low level of potential damage by stripe rust for the eastern Pacific Northwest, fungicide application is not recommended for winter wheat fields unless the disease is observed during the crop season. For spring wheat and barley, resistant and moderately resistant varieties are recommended to plant.

According to WSU, so far, stripe rust has not been reported anywhere in the United States.  By this time of the last year, stripe rust was reported in Louisiana, Texas, and Washington.

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