04/25/05 Rapid stripe rust development

Farm and Ranch April 25, 2005 Wheat growers who planted susceptible varieties of winter and spring wheat need to on the alert for stripe rust. Xianming Chen of the ARS at Pullman says the fungal disease is showing up much earlier this year than last and earlier than normal because of the warmer weather this past winter. He says recent moisture has also been favorable for stripe rust development. Chen says stripe was showing up in western Oregon in February and western Washington in March. Recently stripe rust was found in plots at Pullman, Pendleton, Hermiston and Walla Walla. Chen says a commercial field near Walla Walla had 20 percent stripe rust throughout the field and plants in hot spots had up to 40% rust. The ARS scientist says the stripe rust races are the same or similar to those detected last year in the Pacific Northwest so wheat varieties that were resistant or susceptible last year will be resistant or susceptible this year. Here's Chen's recommendation on when to apply a fungicide. Chen: "If they see stripe rust about 5% severity. That means five percent of the leaf area is covered with rust or five percent of the plants show the infection, then they should spray. Because with early control we are reducing inoculum and protecting other fields, especially the spring wheat fields." Chen says because of the earlier development of stripe rust this year, two fungicide applications may be needed. I'm Bob Hoff and that's the Northwest Farm and Ranch Report on the Northwest Ag Information Network.