Symptoms and Signs
Bacterial soft rots are characterized by softening and water soaking of one or more of the inner fleshy scales of the bulb. Affected tissue is yellow initially, turning brown as the disease progresses lengthwise in the bulb. The neck of infected bulbs may be soft when pressed. These organisms generally appear just before or at the time of harvest or in storage.
Comments on the Disease
Bacterial soft rots are primarily a problem on onions, but not garlic. Free water is essential for entry and spread of the bacteria. Wounds and senescent leaves are the means by which bacteria gain entrance into the bulb. The pathogens are soilborne and may be spread in irrigation water.
Avoid overhead irrigation once onions start to bulb (bulbing occurs about the time the bulb is twice the diameter of the neck). Harvest only after onion tops are well matured. Provide for quick drying following topping, especially if temperatures are high.