Erwinia carotovora subsp. 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 at about the time of harvest or in storage.
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. Harvest only after onion tops are well matured. Provide for quick drying following topping, especially if temperatures are high. The Regents of the University of California.