Incidence and severity of loose smut and surface-borne smuts of barley on the Canadian prairies from 1972 to 2009

Abstract

The barley pathogens Ustilago nuda, U. nigra and U. hordei are seed-borne fungi likely introduced to western Canada on host seed by early European settlers. They initially caused large losses in barley crops, but the development of effective control practices has lessened their impact in western Canada. Monitoring of the incidence and severity of these pathogens in Manitoba, Saskatchewan, and to a lesser extent, Alberta has occurred annually from 1972 to 2009. The mean annual percentage of fields with plants expressing loose smut [U. nuda] was 47% and surface-borne smut [U. nigra and/or U. hordei] was 24%. The average percentage of fields in which plants infected with U. nuda and U. nigra and/or U. hordei were found was 11%. There did not appear to be a relationship in incidence between loose smut-infected plants and surface-borne smut-infected plants. The mean annual percentage of plants per field infected with U. nuda was 0.6%, and with U. nigra and/or U. hordei was 1%. In general, the incidence and severity of these pathogens was greater in an area extending from south central Manitoba, through the northern crop districts of Saskatchewan and Alberta. The incidence of loose smut was greatest during the 1980s and 1990s, but has declined since then, while the incidence of surface-borne smut was greatest in the 1970s, followed by a steady decline in incidence until 1999, after which plants expressing surface-borne smut symptoms were uncommon in western Canada.