Xianming Chen
Stripe rust is developing rapidly in the Pacific Northwest
Thanks to the good moisture in the past three weeks. The winter wheat crop looks good throughout south central and southeastern Washington and northeastern Oregon. However, the moist weather has been favorable for stripe rust development. This year, stripe rust started showing up much earlier than last year and also earlier than normal because of the warmer weather during the winter. Both wheat and barley stripe rusts were reported as early as the first week of February near Corvallis and have developed rapidly in western Oregon. Wheat stripe rust was up to 40% in mid March near Mt Vernon, Washington. This is normal for northwestern Washington. Trace stripe rust was found on Hatton in a winter wheat nursery by Gary Shelton in the first week of April. By April 20, stripe rust on Hatton in that nursery was up to 40% severity (reported by John Burns). On April 19, I found trace stripe rust in our winter wheat nurseries near Pullman, WA. On April 20, I was checking fields and nurseries in southeastern and south central Washington and northeastern Oregon. At the Pendleton Experiment Station, stripe rust just showed up on susceptible checks in our disease monitoring nursery, while at the Hermiston Station, stripe rust up to 5% was easily found on several entries in our disease monitoring nursery and other nurseries. Near Walla Walla, WA, stripe rust was more severe. The susceptible check, ‘PS 279’, had up to 40% stripe rust. I was able to take stripe rust notes throughout several nurseries in that field. This is the earliest time to take stripe rust notes near Walla Walla. The susceptible check, ‘Lemhi’, in the spring nurseries, which were planted next to the winter nurseries and the plants were just at the three-leaf stage, also had stripe rust. A commercial field just outside of Walla Walla to the north had 20% stripe rust throughout the field. Plants in hot spot had up to 40% rust. The early start of stripe rust proved our forecast for the early occurrence of the disease based on the rust situations last year and the weather conditions in the last fall and winter, especially the temperatures higher than normal in last December and January.
Perspective stripe rust impact and control
Based on stripe rust reactions in our disease monitoring nurseries at Walla Walla and Hermiston, and rust samples from Corvallis, stripe rust races are the same or similar to those detected last year in the Pacific Northwest. Therefore, wheat varieties that were resistant or susceptible last year will be resistant or susceptible this year. On April 20, I checked several commercial fields in the Connell area, where severe stripe rust occurred on Hatton in the last two years, but I did not find any rust in these fields, probably because Hatton and other susceptible varieties (such as Buchana and Weston) were not planted. This definitely had positive impact to the rust management in eastern Washington by reducing the disease pressure. Because winter wheat fields were mostly planted with resistant cultivars (such as Eltan, Madsen, and Stephens), stripe rust damage will be minimal in the winter crop, except for limited fields planted with susceptible varieties, for example, the field at Walla Walla mentioned above. Such winter wheat fields planted with susceptible varieties should be sprayed with fungicide as soon as possible. If you still have fields to plant with spring wheat, you better to choose resistant varieties, referring to the seed buy-guide for disease reactions. If you have already planted susceptible or moderately susceptible varieties, get prepared to use fungicides. Because stripe rust has started developing much earlier this year and will develop even more quickly when the weather gets little bit warmer in next several weeks, two applications of fungicide may be needed for both winter and spring crops this year.
Rusts in the nation
So far, wheat stripe rust has been reported in Texas, Louisiana, Arkansas, Oklahoma, Kansas, Alabama, Georgia, California, Oregon, and Washington. The disease developed to 100% in several locations in Texas and Louisiana in the first week of April and continues developing northwards in the Great Plains. The disease is severe in California also. Severity levels were up to 60% and disease incidences were up to 100% in susceptible fields in the first week of April. In the third week of April, up to 90% of stripe rust was observed on susceptible varieties. Leaf rust that usually starts later than stripe rust occurred much earlier this year in the south central and southeastern states. Some of the wheat varieties grown in that region are resistant to stripe rust, but heavily infected by leaf rust. Barley stripe rust has been reported in California and Oregon. The current disease situations throughout the country indicate that 2005 is another year of rusts.
If you have any questions, please feel free to contact me (509-335-8086, xianming@mail.wsu.edu) or David Wood (509-335-4789, dawood@mail.wsu.edu).