How to Manage Pests

UC Pest Management Guidelines

Onion and Garlic

Bacterial Soft Rot

Pathogens: Pectobacterium carotovora ssp. carotovora, P. chrysanthemi, Pseudomonas gladioli, and Enterobacter cloacae.

(Reviewed 1/07, updated 1/07)

In this Guideline:


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.


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.


Cultural Control
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.


[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Onion and Garlic
UC ANR Publication 3453


R. M. Davis, Plant Pathology, UC Davis
B. J. Aegerter, UC Cooperative Extension, San Joaquin County
T. Turini, UC Cooperative Extension, Fresno County
A. Ferry-Abee, UC Cooperative Extension, Tulare and Kings counties

Acknowledgment for contributions to Diseases:
F. F. Laemmlen, UC Cooperative Extension, Santa Barbara and San Luis Obispo counties
R. E. Voss, Vegetable Crops, UC Davis

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