How to Manage Pests

UC Pest Management Guidelines

Almond

Lower Limb Dieback

Pathogens: Unknown

(Reviewed 3/09, updated 3/09)

In this Guideline:


SYMPTOMS AND SIGNS

Beginning in late April, leaves on lower limbs of affected trees first turn yellow, then brown. The limb eventually dies, often right up to the point of attachment, but the large wood of the scaffolds remains apparently unaffected. If the bark on dying limbs is scraped away with a knife, brown spots are evident in the wood. The symptoms can be confused with normal shade-out of low limbs. However, as lower limb dieback progresses, limbs receiving adequate sunlight several feet high in the tree can eventually become affected.

COMMENTS ON THE DISEASE

Padre appears to be the most seriously affected variety, although Butte can also be affected. Less affected are Nonpareil, Carmel, and Aldrich. The occurrence of lower-limb dieback on almonds has been recognized only recently in California and is still being researched. Thus the etiology is unknown, but it may be a physiological disorder related to water potential and light levels. It is believed that affected trees are first weakened by pre-existing root problems, such as overly wet soils in the spring, low light, or possibly other causes including herbicides and fertilizers that may damage tree roots. These predisposed trees are susceptible to infection by secondary pathogens such as Botryosphaeria dothidea and Phomopsis amygdali, or other species that may colonize and eventually girdle the limbs, resulting in limb death. Another possible injury that may be colonized by secondary pathogens includes hull rot infections where dieback occurs.

MANAGEMENT

Good management strategies have not yet been determined. Currently, keeping trees strong by proper irrigation management and maintaining good control of scale populations are the primary recommendations for controlling this disease. Fungicide sprays are not effective.

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Almond
UC ANR Publication 3431

Diseases

J. E. Adaskaveg, Plant Pathology, UC Riverside
W. D. Gubler, Plant Pathology, UC Davis
Roger Duncan, UC Cooperative Extension, Stanislaus County
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center, Parlier
B. A. Holtz, UC Cooperative Extension, San Joaquin County

Top of page


Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2014 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/r3102511.html revised: January 8, 2014. Contact webmaster.