Harvest is in full swing for grain farmers in Washington and Idaho with producers optimistic about spring wheat and barley yields after a high rainfall summer.
But dark clouds loom for some. "Some growers may see a dark cloud rise above their grain harvest combine, and it won't be exhaust," says Diana Roberts, Washington State University Extension specialist in Spokane.
'The culprit is stem rust – a fungus that infests cereal crops late in the season and often goes unnoticed until harvest, when black clouds of spores erupt as the crop is threshed."
Farmers know about another kind of rust, stripe rust, which has become a major problem in the Pacific Northwest, but both rusts infect wheat leaves. Stem rust is caused by a different fungus, as its name suggests. It infests the plant stems as well as the leaves."
"This year scientists have found cereal stem rust widespread in Whitman County (Wash.), especially north of Colfax and Palouse," reports Mike Pumphrey, (cq) WSU spring wheat breeder. "We also found the disease in Spokane and Stevens counties in Washington and Latah County in Idaho."
The problem is due to late season rain, which is rare in the Inland Northwest, reports Xianming Chen, a USDA plant pathologist at WSU . Sometimes the disease can destroy entire fields, he notes.
"Stem rust is most severe this year in late-seeded barley crops, though many spring and winter wheat fields are affected," says Kevin Murphy, WSU barley breeder.
The good news is that the stem rust population in our region is not the race group called Ug99, which was first detected in Uganda in 1998 and has spread to the Middle East and South Africa, according to Les Szabo and Yue Jin, USDA scientists from Minnesota.
Ug99 is virulent against many resistant genes, some of which previously protected wheat against stem rust.
"By now it's too late for farmers to spray for rust in their crops," notes Chen. "We recommend that they select resistant varieties for the next season and avoid planting spring crops late."