EXTENSION PLANT PATHOLOGY

Disease:  Rust of dry bean (Phaseolus vulgaris L.)

Cause:  Uromyces appendiculatus (Pers.) Unger

Symptoms:  Symptoms appear first as raised white to yellow colored circular spots on the leaves.  The spots eventually become larger and form reddish-brown  colored pustules.  A yellow border may surround the enlarged pustules.  Later in the season, the reddish-brown pustules are replaced with dark spots.  The dark spots (teliospores) are the overwintering spores.

Survival and Spread:  The pathogen overwinters in infected residue.  Airborne spores are produced from the residue that can travel many miles.

Favorable Conditions:  Cool to moderate temperatures (65 - 85 F) and free moisture on the leaves from rain or dew or high relative humidity (96%+) are needed for severe disease to occur.  A minimum of 8 hours of these conditions are needed for infection to occur.

Management:  Resistant varieties are available in some dry bean classes.  Rust resistant genes are race-specific, so some resistant varieties may not be resistant to all rust races present.  As of 2004, the Ur3 resistant gene, which is used in the pinto variety 'Maverick', has been effective against bean rust races present in North Dakota.  Foliar fungicides are available for rust control.  Refer to the most recent ND Field Crop Fungicide Guide for information on registered products.  Foliar fungicides should be applied before or at the onset of disease for best results.  

Useful Links:

Rust of Dry Beans (Colorado State University)

Bean Diseases and their Control - Rust (Agriculture and Agri-Food Canada)

Prepared by:  Carl Bradley