Disease Cycle
In many areas, leaf rust requires green volunteer barley to survive between cropping seasons. However, in areas where the alternate host, the weed, Star of Bethlehem (Ornithogalum umbellatum) occurs, teliospores are able to infect the plant. They then can undergo a sexual reproduction cycle and produce aceiospores which can then re-infect barley.
Leaf rust develops rapidly between 15 and 22 C when moisture is not limiting. Following infection, new pustules and spores may be produced within 8 days. Urediniospores are wind-borne and can be spread long distances. Teliospore development occurs later in the season either within uredial sori or within separate telial sori. The teliospores are thick-walled and can persist between crops. Upon germination, they a promycelium (basidium) with four haploid sporidia (basidiospores). The basidiospores can infect both barley and the alternate host.
In western Canada, where the rust cannot overwinter and the alternate host is not present, the fungus may be re-introduced annually as the rust moves northward from the southern United States. In eastern Canada, the alternate host is present, however, infection of barley by aeciospores has not been reported.
Read more about this topic: Leaf Rust (barley)
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