Technical Abstract: Barley (Hordeum vulgare L.) is cultivated over a wider geographic range than almost any other major crop species. It can be found growing from the tropics to the high latitudes and from the seacoast to the highest arable mountaintops. On marginal lands where alkaline soils, drought, or cold summer temperatures occur, barley can outproduce most other cereal crops (Mathre 1997). Over such a wide range of growing environments, it is not surprising that barley will encounter different plant pathogens and succumb to various diseases. Considering the hundreds of thousands of potential plant pathogenic microorganisms that exist in the world, resistance is the rule and susceptibility the exception in the plant world. Such is also the case with barley as just over 125 pathogens have been reported on the crop or its products in the United States (Farr et al. 1989). Mathre (1997) lists about 80 different diseases caused by infectious agents in his Compendium of Barley Diseases, but of this number, only a handful consistently cause widespread economic loss on an annual basis.