How to Manage Pests

UC Pest Management Guidelines

Onion and Garlic

Basal Rot

Pathogen: Fusarium oxysporum f. sp. cepae

(Reviewed 1/07, updated 1/07)

In this Guideline:


Plants affected by basal rot show progressive yellowing and dieback from the tips of leaves. Affected roots are dark brown to dark pink. A white fungal growth is sometimes evident at the base of infected bulbs. When an infected bulb is cut vertically, a brown discoloration of the stem plate tissue is apparent. Later, the stem plate tissue becomes pitted and shows a dry rot. Under dry conditions, the stem plate and dry outer scales crack open. Basal rot can continue in storage.


The fungus survives indefinitely in soil. Infection occurs through wounds or in the vicinity of old root scars at the base of the bulb. The disease is favored by soil temperatures in the range of 57° to 90°F, with optimum temperatures being 79° to 82°F. Basal rot is more prevalent in transplanted onions than in direct-seeded onions.


Cultural Control
Avoid fields with a history of basal rot problems and rotate 3 to 4 years out of onions, garlic, and leeks. Control soil insects and foliage diseases. Cure onions properly before storage. Store at cool temperatures since infection is favored by warm conditions.


[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

Top of page

Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2016 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

Accessibility   /PMG/r584100611.html revised: June 22, 2016. Contact webmaster.