White Mold of Dry Beans

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One of the most important diseases affecting dry beans in western Nebraska and Colorado is white mold caused by the fungus Sclerotinia sclerotiorum. In recent years, losses from this disease have averaged as high as 20 percent, with a few individual field losses exceeding 65 percent.
White mold is first observed as wet, soft spots or lesions on infected leaves, branches, stems and pods. These lesions enlarge into a watery, rotten mass of tissue that is covered by a white moldy growth. Infection of stems and branches will cause affected plant parts to wilt and later die, taking on a bleached and dried appearance. This bleaching symptom is characteristic of white mold infected pinto and great northern types and differs from the normal tan color resulting from senescence (aging) or other diseases. Black and irregularly-shaped sclerotia (resting structures of the fungus) form on and within infected plant parts.

H.F. Schwartz
J.R. Steadman
D.S. Wysong
E.D. Kerr
Colorado State University Extension