WHEAT RUST EPIDEMICS IN WESTERN CANADA IN 1953, 1954 AND 1955

Abstract

Leaf rust and stem rust of wheat (Puccinia triticina Erikss. and P. graminis Pers. f. sp. tritici Erikss. and Henn.) were abundant in the Prairie Provinces of Canada in 1953, 1954 and 1955. Considerable rust damage was caused in all 3 years but particularly in 1954, when both rusts were heavy throughout most of Manitoba and Saskatchewan and in a considerable area in east-central Alberta. In all 3 years, seeding was late and spores arrived early. Abundant moisture favoured rust development throughout the entire seasons of 1953 and 1954 and during the first half of the 1955 season.In 1953, as a consequence of early arrival of rust spores and an extended period of rainy weather, rust losses were greater than in any year since 1935. Much the greatest damage was caused to durums. In 1954, late seeding, much above normal precipitation over wide areas, and a great northward movement of rust spores at an early date into Saskatchewan, where most of the wheat is grown, resulted in the most severe and widespread rust epidemic in Canada's history. In 1955, high rainfall, late seeding, and a northward movement of rust spores favoured the early establishment of leaf and stem rust, especially in Manitoba. Subsequent rust development was mitigated by two factors: first, the onset of hot, dry weather about mid-July, which hastened crop maturity and retarded rust spread; and second, the presence of a large acreage in Manitoba and eastern Saskatchewan of the stem- and leaf-rust-resistant variety Selkirk and the leaf-rust-resistant variety Lee, which greatly limited the increase of inoculum of both rusts.It is estimated that leaf rust and stem rust reduced wheat yields in Western Canada by upwards of 45 million bushels in 1953; 150 million bushels in 1954; and 9 million bushels in 1955.