How to Manage Pests
UC Pest Management Guidelines
Pathogen: Pseudomonas syringae
In this Guideline:
Symptoms are most obvious in spring and include
limb dieback with rough cankers and amber-colored gum. There may also be leaf
spot or blast of flowers and young shoots. The sour sap phase of decline may not
show gum and cankers, but the inner bark can be brown, fermented, and sour
smelling. Flecks and pockets of bacterial invasion in bark occur outside
canker margins. Frequently, infected trees sucker from near ground level; cankers do not extend
Pseudomonas syringae survives in or on plant surfaces and is spread by
splashing rain. It is favored by high moisture and low temperatures in spring.
The disease is worse in low or sandy spots in the orchard. Vigorous trees are
less susceptible to bacterial canker. Young trees, 2 to 8 years old, are most
affected. The disease rarely occurs in first year of planting and is uncommon
Planting trees that are budded or grafted about 32
inches above the root crown can help suppress bacterial canker infections.
Properly irrigate and fertilize young trees during the growing season. Trees on
Lovell peach rootstock are more resistant than others; and those on plum
rootstocks are most susceptible. Delayed pruning may help. In light, sandy
soils and some heavy soils, successful control has been achieved with preplant
fumigation for nematodes. Application of copper during dormancy has not been
shown to protect against bacterial canker in California.
Bactericide applications have no reliable effect
on bacterial canker and their use is not recommended. Preplant fumigation for
nematode control reduces the severity of bacterial canker in newly planted
orchards. Nematodes stress trees, which predisposes them to bacterial canker.
The benefits of preplant soil fumigation for control of bacterial canker
usually lasts only a few years; in some areas only limited improvements in
disease control occur following soil fumigation. For additional information,
||Amount to Use
choosing a pesticide, consider information relating to environmental impact Not all registered pesticides are listed. Always read label of product being used.
Must be applied under a Critical Use Exemption only. Use higher rates for
fine-textured soils. Fumigants such as methyl bromide are a prime source of
volatile organic compounds (VOCs), which are a major air quality issue.
Fumigate only as a last resort when other management strategies have not been successful or are not available.
UC IPM Pest Management Guidelines: Prune
UC ANR Publication 3464
W. D. Gubler, Plant Pathology, UC Davis
J. E. Adaskaveg, Plant Pathology, UC Riverside
C. Pickel, UC IPM Program, Sutter/Yuba counties
W. H. Olson, UC Cooperative Extension, Butte County
F. J. A. Niederholzer, UC Cooperative Extension, Sutter/Yuba counties
Acknowledgment for contributions to Diseases:
B. L. Teviotdale, Kearney Agricultural Center, Parlier
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