Puccinia striiformis f. sp. hordei

Barley stripe rust is a fungal disease of barley caused by Puccinia striiformis f. sp. hordei. a forma specialis of Puccinia striiformis. It was first detected in the United States in 1991, in northern and eastern Idaho in 1993, In 1995 it was detected for the first time in western Washington and western Oregon and is currently considered to be well established there. The disease initially develops at a small loci within a field and spreads rapidly and has caused significant losses in areas where climatic conditions are cool and wet.

from Wikipedia