Scab of Wheat and Barley
During the past 15 years, scab has severely damaged soft red winter wheat crops in several Corn Belt states, hard red spring wheat and spring barley in the Red River Valley of the northern plains, and soft white wheats in Michigan, New York, and Ontario. In Indiana, scab was a major problem in 4 of the past 10 years: 1986, 1990, 1991, and 1995. Scab is not a new disease. J. C. Arthur, the first plant pathologist at Purdue, described the disease in 1891. He said the disease was new to science but was familiar to farmers as "scab." Until the last decade, scab was regarded as a sporadic disease that might be seen only once in 1 0 or 15 years, and then only in scattered fields. It is now regarded as a chronic disease in the eastern half of the US and one of the most critical problems for production of quality wheat and barley. Development of scab is sensitive to weather. Several fungi of the genus Fusarium cause scab, but the principal pathogen is Fusarium graminearum. This fungus is a pathogen of corn (Gibberella ear and stalk rot) as well as wheat and barley. The main site for infection of wheat and barley is the anthers just after flowering. If weather is wet and warm when the crop is flowering, and there is a local source of abundant fungal inoculum, a high incidence of infection will result.