Leaf rust is common disease in winter wheat mainly in Saskatchewan and Manitoba. With round lesions largely confined to the leaves, they should be easy to spot; however, they are much smaller than those of stem rust. Each pustule develops orange-red unrediniospores and as the plant matures the pustules will darken.
Spores can overwinter on straw and germinate in the spring. In Western Canada, leaf rust infections are usually observed in June and will peak in August. Resistant cultivars are avialble and folicur fungicides are effective in treating leaf rust. Spraying is recommended if the threshold is met in three of five spots sampled in the field.
Stem rust, like leaf rust, is also more common in Saskatchewan and Manitoba, but instead of pustules forming on the leaves, you will see them on the stem, and they will have a darker, brick red colour. As the plant matures, pustules will darken to a black colour.
Spores can be seen in southern Manitoba and Saskatchewan in mid to late July. The severity of the disease will depend on weather conditions, time of arrival, and growth stage of crops, and it will rarely overwinter. Resistant cultivars are avialble and folicur fungicides are effective in treating stem rust at the very early stage of disease development.
Stripe rust is a disease more common to Alberta that can defoliate and shrivel kernels. With this disease you will see elongated yellow pustules that develop on leaves and extend lengthwise on the leaf. This disease will affect juvenile and adult leaves as well as the kernels.
Stripe rust can overwinter in a mild winter. It is best to scout for stripe rust from emergence in fall 35 to 45 days before harvest. Resistant cultivars are avialble and folicur fungicides are effective in treating stripe rust.