Plant Disease Notes: Rust of Garden Beans - Garden Plant Rust Disease

ANR-1008 Revised May 2004. Edward J. Sikora, Extension Plant Pathologist, Professor, Entomology and Plant Pathology, Joseph M. Kemble, Extension Horticulturist, Associate Professor, Horticulture, both with Auburn University, and Ellen M. Bauske, former Extension Associate.

Rust, caused by the fungus Uromyce phaseoli var. typica, attacks all aboveground plant parts but is most commonly seen on the lower surface of leaves. Rust is a common problem on snap beans but rare on lima beans in Alabama. Rust can cause significant yield losses when plants are attacked early in the season.
Symptoms. Rust is most common on mature plants. It is usually observed on leaves but may also occur on pods. The initial symptom of rust is small, white, slightly raised spots on the lower leaf surface. These pimple-like structures may be surrounded by a yellow halo. Within 1 week these pustules break open into rust-colored lesions, about the size of a pinhead. The powdery mass of rust colored spores will give a rust color to the fingers if rubbed across symptomatic leaves. These lesions will appear on the lower and upper leaf surface. About 1 week after the pustules appear, the entire leaf begins to turn yellow. Heavily infected leaves turn yellow, shrivel, dry up, and drop prematurely. A severely infected field looks scorched.

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