Geographic distribution of common root rot and Bipolaris sorokiniana in Queensland wheat soils

Abstract

A survey to determine the geographic distribution of common root rot in Queensland wheatgrowing areas was conducted in 1978, 1979 and 1980. In 1980, soil populations of Bipolaris sorokiniana were determined from the areas where common rot was assessed. Common root rot was found in all areas and was most severe in the South-western Downs, Western Downs and Northern Darling Downs and least severe in the Central Highlands. Incidence of common root rot over all areas changed from 77% in 1978, to 65% in 1979, and to 56% in 1980. This was mostly due to a reduction from 91 to 44% on the Darling Downs. The lower incidence in 1979 and 1980 was thought to be associated with lower rainfall in those years and in some areas with an increase in rotation to crops other than winter cereals. Severity of common root rot was significantly lower only in 1979. In general, the severity of common root rot in Queensland was higher than that recorded in Canada and lower than that recorded in Brazil. Soil populations of B. sorokiniana varied from 0 to 320 propagules per gram of soil with an overall mean of 58. They were highest in the Western and Southwestern Downs, and lowest in the Central Highlands. In general, the size of the populations were less than those recorded elsewhere.