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Bacterial Soft Rots of Onions and Garlic

Bacterial soft rots are primarily a problem on onions, but not garlic. They 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. A foul-smelling odor is also associated with these disorders.

Solutions

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. 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.

Garlic bulbs with bacterial soft rot caused by Erwinia carotovora. From Kern Co.   Credit: Jack Kelly Clark, UC IPM
Rotting of garlic bulbs. Credit: Jack Kelly Clark, UC IPM
Garlic bulbs with bacterial soft rot caused by Erwinia carotovora. Longitudinal section showing rot of root plate, cross sections showing of inner scales. From Kern Co.  Credit: Jack Kelly Clark, UC IPM
Rotting of inner fleshy tissue. Credit: Jack Kelly Clark, UC IPM
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