Bean Rust

Rust is a common disease that affects many plants. Bean rust is caused by Uromyces phaseoli typica, and it affects common dry and snap, lima, and scarlet runner beans. It is a worldwide disease, and can destroy an entire crop if conditions are favorable early in the season. It is more severe in humid areas, and is favored by moderate temperatures. It can cause defoliation early in the season, which reduces yield. If only the leaves are infected later in the season, there is little yield loss, and the need for a chemicabean rustl defoliant may be eliminated.

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

References:

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.

The information in this material is for educational purposes. The recommendations contained are based on the best available knowledge at the time of printing. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension system does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations as of the date of printing. If the information does not agree with current labeling, follow the label instructions. The label is the law.Warning! Agrochemicals/pesticides are dangerous. Read and follow all instructions and safety precautions on labels. Carefully handle and store agrochemicals/pesticides in originally labeled containers immediately in a safe manner and place. Contact the Connecticut Department of Environmental Protection for current regulations.The user of this information assumes all risks for personal injury or property damage.Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kirklyn M. Kerr, Director, Cooperative Extension System, The University of Connecticut, Storrs. The Connecticut Cooperative Extension System offers its programs to persons regardless of race, color, national origin, sex, age or disability and is an equal opportunity employer.

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