Stripe Rust Is Developing on Winter Wheat in Central Washington and Northeastern Oregon

May 6, 2004

Xianming Chen

Stripe rust started showing up in the last week of April on winter wheat in experimental plots near Hermiston (Umatilla County), Oregon and in commercial fields near Connell (Franklin and Adams Counties), Washington. Mathias Kolding, a cereal breeder of Oregon State University, observed a few pustules of stripe rust on one of his wheat lines at the Hermiston Experiment Station. By May 5, severity levels up to 10% were observed on two of the wheat lines and one pustule was found on a Triticale line. Near Connell, Washington, severity levels of stripe rust up to 20% were observed in fields planted with ‘Hatton’, a hard red winter wheat that were severely damaged last year. This year, stripe rust appearance was much later than last year in this region, due to the dry weather last fall that reduced fall infection and cold winter that reduced winter survival. Most of infected leaves were the top leaves, indicating that infections occurred mostly after the winter. Only very few “hotspots” consisting about 5 to 10 tillers had rust from the bottom to flag leaves. Less than 5% of plants had rust. In contrast, by this time of last year, 100% of plants were infected and over 90% of severity levels were on plants of “hotspots” of over 10-foot in diameter. Stripe rust was not found in the ‘Finley’ hard red winter wheat fields. Because of less acreage of ‘Hatton’ wheat and the dry weather in April and forecasted for next 10 days for central Washington, the ‘Hatton’ wheat fields will have less damage than last year. However, these fields will produce rust spores to infect spring wheat crops in the central and further to eastern Washington and northern Idaho. Therefore, spring crops will be vulnerable to stripe rust infection. We will start to see stripe rust in spring wheat fields in central and eastern Washington, northeastern Oregon, and Northern Idaho in two to four weeks. How severe the epidemic levels will depend upon the weather conditions mainly the precipitation from now to late June. Temperature will not be a problem from now to early June. Spray the Hatton fields may not be justified based on economic returns on the basis of individual fields because of the poor crop stand. However, it will reduce inoculum for spring crops for the Pacific Northwest. If you grower susceptible spring wheat varieties, you should start to check your fields for stripe rust in three to four weeks. If your fields are under irrigation, you should check for stripe rust sooner. If you see about 5-10% of either rust severity (percent of leaf areas infected) or incidence (percent of plants infected), you should consider use of fungicide. Tilt, Quadris, Quilt, Headline, and Stratego are available for control of stripe rust. If you have any questions, please contact me (Phone: 509-335-8086, E-mail: xianming@mail.wsu.edu) or David Wood (Phone: 509-335-4789, E-mail: dawood@mail.wsu.edu).