Bacterial soft rots affect many plants including begonia, carnation, daffodil, geranium, impatiens, and zinnia. Soft rot bacteria cause infected tissue to turn brown, become mushy, and develop an unpleasant odor. Stem tissue turns brown and deteriorates near the soil. Plants grow slowly and seedlings collapse. Bacterial spots often start out as tiny water-soaked areas on leaves, stems, or blossoms. Spots or blotches turn dark gray or blackish as they enlarge and sometimes have yellow borders. Initial spots are circular but may become angular and coalesce and cause plant tissue death or necrosis. Cankers may form on stems. Under wet conditions, infected tissue may exude brownish masses of bacteria. Dead tissue may tear out, leaving holes and a ragged appearance.
Pathogens causing spots, blights, and soft rots can also cause vascular wilt if the infecting bacteria become systemic. Aboveground plant parts yellow, droop, wilt, and die.
Solutions
Use disease-free cuttings, corms, and other stock. Avoid planting too deeply. Provide good drainage. Do not overwater and avoid overhead irrigation. Keep foliage dry and provide good air circulation. Don’t crowd plantings. Bacteria commonly infect through wounds, so avoid injuring plants. Use good sanitation. Regularly inspect plants for disease and remove infected plants immediately. Some cultivars are more susceptible to infections than others. Seek information on resistant cultivars and consider planting them.
