Edward J. Sikora, Extension Plant Pathologist, Associate Professor, Plant Pathology, Auburn University Plant Disease Notes Bacterial Soft Rot of Sweet Potatoes Bacterial soft rot, also known as bacterial stem and root rot, is caused by the pathogen Erwinia chrysanthemi. Rotting can occur in the field as well as during shipment and storage. Roots are infected in the field or more commonly in storage by a soft rot that turns diseased tissue light brown and watery. Lesions on storage roots often have a dark brown margin.
Some storage roots appear healthy from the outside but are decayed internally.
Infected roots show black streaks in the vascular tissue and eventually undergo a soft, moist decay. Mother roots often decay in plant beds. In the field, brown to black, water-soaked lesions appear on stems and petioles. Eventually, the stem may become watery and collapse, causing the ends of vines to wilt. Usually, one or two vines may collapse, but occasionally, the entire plant dies.