University of Idaho wheat breeder Ed Souza is asking southern Idaho wheat growers to check their fields for stripe rust. This fungus-which produces yellow-orange stripes that rub off on growers' hands and clothes-is changing so rapidly that Souza wants to know which of about 100 different genetic types or "races" may be lurking in southern Idaho wheat fields.

"It's important to check the spring wheat crop to see if any of the new races have shown up," he says.

Stripe rust has been reported in southern Idaho grain fields this year but Souza hasn't received samples to identify. In northern Idaho, infestation levels in susceptible wheat varieties have reached 10 to 20 percent and will likely climb to 50 to 60 percent, he says. In Moses Lake, Wash., susceptible varieties already have 100 percent of their leaf area covered.

What's more, varieties that resisted earlier stripe rust races as recently as last year are apparently falling prey to new fungal races in northern Idaho and Washington. These varieties include the soft white spring wheats Wawawai, Treasure and Pomerelle. In the Columbia Basin, the disease's virulence is slowly overcoming Moreland's adult plant resistance. Even in Alturas, stripe rust is taking its toll on 10 to 15 percent of plants, while 85 to 90 percent remain healthy. That indicates a variability in Alturas' genetically based resistance, Souza says.

For Souza, the good news is that trials for stripe rust resistance in UI wheat breeding lines are under way in Moscow and in Mt. Vernon and Pullman, Wash., where disease pressure is high. Souza says intense disease pressure-particularly by new stripe rust races-will give breeders critical information on the ability of their lines to withstand the rapidly changing disease. In a new initiative with the UI, the Idaho Wheat Commission recently funded Xianming Chen, a research plant pathologist with the USDA Agricultural Research Service in Pullman, to comprehensively test early-generation breeding materials.

Southern Idaho wheat growers who find stripe rust in their fields should contact their UI Extension educator or call Souza at 208-397-4162, Ext. 123.