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Epidemiology of Barley Yellow Dwarf in Manitoba and Effect of the Virus on Yield of Cereals. C. C. Gill, Research Scientist, Canada Department of Agriculture, Research Station, 25 Dafoe Road, Winnipeg 19, Manitoba, Canada. Phytopathology 60:1826-1830. Accepted for publication 23 July 1970. DOI: 10.1094/Phyto-60-1826.

In 1969, barley yellow dwarf virus (BYDV) caused an estimated loss of 1,380,860 bushels of two-rowed Herta barley in an area of approximately 2,700 square miles in Manitoba. Losses on other cereals were also high. In a germination test, seed from infected barley produced seedlings of poor vigor. Two strains of the virus, one transmitted specifically by Rhopalosiphum maidis and the other transmitted nonspecifically by three other species of aphids, were chiefly responsible for the epidemic. Early migration of the aphid vectors and the prevalence of late-seeded crops contributed to the severity of the disease. A high proportion of plants in the field carried BYDV without showing symptoms. The proportion was highest for barley infected with the R. maidis-specific strain.