Wheat leaf rust found in several fields - June 2006

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Leaf rust (Puccinia recondita f.s. tritici) was found in several wheat fields near Holland, Michigan this week. (see photos) When rust severity is high, as it was in these locations, one of the most noticeable symptoms for anyone walking the field is that their hands or clothing become covered with a powdery orange dust from the spores. There can be substantial differences among wheat varieties in their levels of resistance to leaf rust. Fields in the vicinity planted with other varieties did not show any symptoms of the disease. Leaf rust has not been found to any great extent in Michigan for several years, and so far, has not been reported from any other locations.

It is possible for leaf rust to overwinter during a mild winter such as we experienced this past year. The leaf rust fungus needs living leaf tissue to survive. It does not survive in the soil or in crop residue. It can move to volunteer wheat in the summer after harvest, and travel to newly planted wheat in the fall. In locations where it has overwintered, it is most severe on the bottom leaves. Usually, rust travels to Michigan on storms from the Gulf Coast area. When it blows in from distant locations, it will be most severe on upper leaves. Rust typically occurs uniformly across a field. During favorable weather conditions, rust seems to explode, as spores are produced and create additional infections in the field. Infection can take place in as little as four hours under favorable conditions. Rust development during spring is favored by daytime temperatures between 60° and 75° F, and light rain or dew. Heavy rain tends to wash spores off the leaves. Dispersal of spores to upper leaves and between fields is favored by dry, windy conditions. Rust infections can be spread by human activity and equipment that has been in infected fields. Practice good sanitation by power washing equipment that has come into contact with the spores before using it in a clean field. Similarly, avoid wearing clothing contaminated with spores into clean fields.

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