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How to Manage Pests
UC Pest Management Guidelines
Citrus
Psorosis
(Reviewed 7/03,
updated 7/03)
In this Guideline:
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SYMPTOMS
Infected trees, mostly orange and grapefruit, slowly decline; main scaffold
branches die and trees become unproductive. The most distinguishing field
symptom is scaling and flaking of
the bark on the scion cultivar. During early stages, patches of bark on the
trunk or scaffold branches show small pimples or bubbles, which later enlarge
and break up into loose scales. Gumming often appears around the margins of a
lesion. In advanced stages, deep layers of bark and the wood become impregnated
with gum and die.
COMMENTS ON THE DISEASE
Psorosis is a graft transmissible disease, caused by a virus, most often found
in old citrus plantings. It is transmitted in infected budwood or possibly with
contaminated grafting tools. Occasionally, the disease spreads through root
grafting from an infected to a healthy tree. Seeds of some citrange cultivars
are known carriers of the disease.
MANAGEMENT
As with other graft transmissible diseases, the use of disease-free budwood is
the major method for preventing damage from psorosis. The Citrus Clonal
Protection Program provides budwood free of major diseases to nurseries and
growers. Where an old tree shows symptoms, scrape away the infected bark area
to stimulate the formation of wound callus, which results in temporary
recovery. Generally, a psorosis-infected tree will produce less, and
replacement is the best option.
![[UC Peer Reviewed]](/IMAGES/logo-ucpeerreviewed.jpg)
UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441
Diseases
H. D. Ohr, Plant Pathology, UC Riverside
J. A. Menge, Plant Pathology, UC Riverside
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