Symptoms: Rust can occur on all above-ground parts of the plant, but rust spots are most numerous on the undersides of leaves. Spots begin as tiny, white, slightly raised spots. These will break open to become distinct round reddish brown spots. When touched, reddish brown dust-like spores brush off. The spots are surrounded by yellow rings on some bean varieties. If the leaves are severely covered, they fall off. In late season, spots may darken as the black over wintering spores are produced.
Prevention: Rotate away from any bean for two years. Plow debris under right after harvest. Resistance is available for this disease, although there are many races of the fungus. Many varieties are resistant to a few races, but few varieties are resistant to most races. See current recommendations for chemical control measures.
By Pamela S. Mercure, IPM Program Assistant, University of Connecticut, 1998
Sherf, A.F. and A. A. MacNab. Vegetable Disease and Their Control. John Wiley and Sons, New York. 1986
Stavely, J.R. Rust. pp. 24-25 in Compendium of Bean Diseases. R. Hall, ed. APS Press, St Paul, MN. 1991.
This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.
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