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How to Manage Pests
UC Pest Management Guidelines
Cherry
Bacterial Canker
Pathogen: Pseudomonas syringae
(Reviewed 11/09,
updated 11/09)
In this Guideline:
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Symptoms are most obvious in spring, and include limb die back 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. Flecks and pockets of bacterial invasion in bark
occur outside canker margins. Frequently, trees sucker from near ground level; cankers do not
extend below ground.
Pseudomonas syringae
survives on plant surfaces, is spread by splashing rain, and 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,
while young trees, 2 to 8 years old, are most affected. The disease rarely
occurs in first year of planting, and is uncommon in nurseries.
The occurrence of bacterial canker is thought to be related to the
amount of stress trees are subjected to, including poor nitrogen/microelement
availability, high ring nematode populations, previous drought stresses,
hardpan, rootstocks that reduce tree vigor, spring freezes, and irrigation methods
that wet the tree. If ring nematode populations are present in an orchard site,
preplant fumigation is important. Also important are rootstock selection,
proper nitrogen fertilization, and the use of drip or microsprinkler irrigation,
which may help with nutrient uptake. Of the rootstocks commonly used for
cherries in California, Mahaleb is the most tolerant of bacterial canker, Colt
is moderately susceptible, and Mazzard is susceptible. Spring/summer pruning
may also help. Fall and dormant season copper
sprays have been used by some growers to help manage this disease, but research
in California orchards has not shown this practice to be consistent or reliably
effective.
Treatment Decisions
In light, sandy soils and in some heavy soils, control has been achieved
with preplant fumigation for nematodes. Ring nematodes predispose cherry trees
to bacterial canker. The benefits of preplant soil fumigation for control of
bacterial canker usually last only a few years; in some areas only limited improvements
in disease control occur following soil fumigation.
| Common name |
Amount/Acre |
R.E.I.+ |
P.H.I.+ |
| (trade name) |
|
(hours) |
(days) |
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| The following materials are listed in order of usefulness in an IPM
program, taking into account efficacy.
When choosing a pesticide, also consider information relating to environmental
impact. Not all registered pesticides are listed. Always read label of product being used. |
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| PREPLANT |
| A. |
METHYL BROMIDE* |
300–600 lb |
see label |
NA |
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COMMENTS: Use allowed under List of
Approved Critical Uses. Use higher rates for fine-textured soils. Fumigants
such as methyl bromide are a source of volatile organic compounds (VOCs) but
are not reactive with other air contaminants that form ozone; methyl bromide
depletes ozone. Fumigate only as a last resort when other management strategies have not been successful or are not available. |
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UC IPM Pest Management Guidelines: Cherry
UC ANR Publication 3440
Diseases
J. E. Adaskaveg, Plant
Pathology, UC Riverside
J. L. Caprile, UC Cooperative Extension, Contra Costa County
Acknowledgment for contributions to Diseases:
W. D. Gubler, Plant Pathology, UC Davis
B. L. Teviotdale, Kearney Agricultural Center, Parlier
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