How to Manage Pests

UC Pest Management Guidelines

Apricot

Bacterial Canker

Pathogen: Pseudomonas syringae

(Reviewed 10/14, updated 10/14)

In this Guideline:


SYMPTOMS AND SIGNS

Symptoms are most obvious in spring, and include limb dieback with rough cankers and amber colored gum. There may also be leaf spot and blast of young flowers and shoots. The sour sap phase of bacterial canker may not show gum and cankers, but the inner bark is brown, fermented, and sour smelling. Orange or red flecks and pockets of bacterial invasion under the bark occur outside canker margins. Frequently, trees sucker profusely from near ground level or on the limbs below infected areas; cankers do not extend below ground.

COMMENTS ON THE DISEASE

Pseudomonas syringae survives on plant surfaces, is spread by splashing rain, and is favored by high moisture and low temperatures in spring. The bacterium is commonly found on healthy as well as diseased plants and becomes pathogenic only on susceptible or predisposed trees.

The disease is found almost exclusively in replanted orchards where ring nematodes flourish or in locations where spring frost is a problem. The disease is worse in low, gravelly, sandy spots, soils with shallow claypans (2-3 feet deep), or other soil conditions that lead to weakened growth. Vigorous trees are less susceptible to bacterial canker, while young trees (2–8 years old) are most affected. The disease rarely occurs in the first year of planting unless the ground is not fumigated before planting. It is uncommon in nurseries.

MANAGEMENT

The key to bacterial canker management is control of ring nematodes and maintaining healthy, vigorous trees. Any management practice that improves tree vigor (e.g., lighter, more frequent irrigation with drip or microsprinklers, improved tree nutrition [especially nitrogen], etc.) will help reduce the incidence of this disease.

It is very important to fumigate sandy soils when apricot trees are to be planted following an old apricot, peach, almond, or other Prunus spp. orchard. Rootstocks of plum parentage (e.g. Myrobalan, Marianna 2624) are highly susceptible to bacterial canker. Lovell peach rootstocks are more tolerant than Nemaguard or apricot rootstocks. In soils with high levels of ring nematodes, annual fall treatments with a nematicide are beneficial. There is evidence that pruning during the dormant period may make trees more susceptible than pruning after trees become active in spring or pruning in summer. Copper sprays applied at the beginning and end of leaf fall have been tried with highly variable results &—resistance to copper may be a factor.

Management Decisions

In light, sandy soils and in some heavy soils, control has been achieved with preplant fumigation for ring nematodes. Nematodes stress trees, which predisposes them to bacterial canker. The benefits of preplant soil fumigation for control of bacterial canker usually last only a few years.

Common name Amount per acre REI‡ PHI‡
(Example trade name)   (hours) (days)

UPDATED: 10/14
Calculate impact of pesticide on air quality
When choosing a pesticide, consider its usefulness in an IPM program by reviewing the pesticide's properties, efficacy, application timing, and information relating to resistance management, honey bees, and environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
 
PREPLANT
 
A. 1,3-DICHLOROPROPENE* / CHLOROPICRIN*
  (Telone C35) Label rates See label 0
  COMMENTS: Chloropicrin tends to invigorate young trees, which can be advantageous in replant situations and where one Prunus orchard replaces a previous one. This restricted use product is applied only by professional fumigation companies. In California the applications must be applied to soils having a moist surface; this task is difficult to achieve without use of sprinklers unless there is a fortunate rainfall. Do not flood irrigate prepared lands to achieve this surface moisture requirement. Broadcast apply where nematode resistance is unavailable for prevailing nematodes. Fumigants such as 1,3-dichloropropene and chloropicrin are a source of volatile organic compounds (VOCs), but are minimally reactive with other air contaminants that form ozone.
 
B. 1,3-DICHLOROPROPENE*
  (Telone II) 33.7 gal/broadcast acre See label NA
  COMMENTS: This restricted use product is applied only by professional fumigation companies. In California the applications must be applied to soils having a moist surface; this task is difficult to achieve without use of sprinklers unless there is a fortunate rainfall. Do not flood irrigate prepared lands to achieve this surface moisture requirement. Broadcast apply where nematode resistance is unavailable for prevailing nematodes. Fumigants such as 1,3-dichloropropene are a source of volatile organic compounds (VOCs), but minimally reactive with other air contaminants that form ozone.
 
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
NA Not applicable.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Apricot
UC ANR Publication 3433

Diseases

J. E. Adaskaveg, Plant Pathology, UC Riverside
W. D. Gubler, Plant Pathology, UC Davis
W. W. Coates, UC Cooperative Extension, San Benito County
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center, Parlier
J. L. Caprile, UC Cooperative Extension, Contra Costa County
B. A. Holtz, UC Cooperative Extension, Madera County
K. M. Kelley Anderson, UC Cooperative Extension, Stanislaus County

Acknowledgment for contributions to Diseases:
B. L. Teviotdale, Kearney Agricultural Center, Parlier

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/r5101011.html revised: April 15, 2016. Contact webmaster.