Xianming Chen
As of today, we have almost completed recording stripe rust data in our winter and spring crop nurseries at various locations in Washington. Stripe rust developed to 100% severity on susceptible winter wheat varieties in all nurseries and up to 80% severities on spring wheat nurseries in Lind, Walla Walla, and Central Ferry and to 100% on susceptible spring wheat varieties in the Mount Vernon and Pullman fields (Figure 1). Barley stripe rust developed up to 80% in nurseries at Mount Vernon and Pullman locations.
Figure 1. Severe stripe rust on susceptible spring wheat plants in spreader rows surrounding spring wheat germplasm screening nurseries under natural infection in an experimental field near Pullman, WA. The picture was taken on July 8, 2024.
As most wheat-growing areas in the eastern Pacific Northwest have had hot and dry weather conditions in the past week and the forecast weather for the next 10 days will be continually hot and dry, stripe rust has started to slow down and stop. With winter crops are maturing and spring crops have generally passed the flowering stage, application of fungicides for controlling stripe rust for this growing season is over except for late-planted spring wheat fields at high elevations and/or under irrigation. Without 3-5 hours of dew formation or temperatures below 73oF, the stripe rust fungus will not be able to infect plants. These conditions can be used to determine if new infections can occur and if fungicide application is needed or not.
Nationwide, wheat stripe rust has been reported in over 30 states, including Louisiana, Texas, Washington, Arizona, Oregon, Georgia, Mississippi, Alabama, North Carolina, Oklahoma, Kansas, California, Virginia, Nebraska, Indiana, Illinois, Kentucky, Tennessee, Arkansas, Maryland, Idaho, Michigan, New York, South Dakota, North Dakota, Utah, Missouri, Wisconsin, Montana, and Minnesota. Barley stripe rust has been reported in California and Washington.