May 4, 2023
Dr. Xianming Chen (USDA-ARS Plant Pathologist) released a very brief Stripe Rust Update May 1, 2023, saying that stripe rust pressure is currently low, similar to last year at this time. Recall that he predicted yield loss of 20-40% in the last update in early April.
Dr. Chen’s forecast also states that they did not find stripe rust in their monitoring nursery in Walla Walla or commercial fields in Benton, Columbia, Garfield, or Walla Walla Counties and Umatilla County, OR during their April 28 survey. As happened last year, stripe rust is getting a late start again this year.
Although this is good news and we are not recommending prophylactic fungicide application, stripe rust can develop very quickly when conditions are favorable. Therefore, we recommend scouting fields for the presence of stripe rust, especially susceptible varieties, and consider fungicide application when 1-5% of plants have active rust (yellow-orange sporulation on leaves). Given the current forecast, winter and spring varieties with a stripe rust rating of 4 or less should not require fungicide application, but those rated 5 and above should be monitored and sprayed if rust develops.
I will provide more rust updates as weather conditions change and new predictions are released. In the meantime, you can find additional information about stripe rust, including photos showing rust percentage, on the WSU Wheat and Small Grains website.
For questions or comments, contact Tim Murray via email at tim.murray@wsu.edu, via phone at (509) 335-7515, or by following him on Twitter @WSUWheatDoc.