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UC Pest Management Guidelines

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Potato

Calico

Pathogen: Alfalfa mosaic virus (AMV)

(Reviewed 8/07, updated 8/07)

In this Guideline:

Symptoms
Comments on the disease
Management

SYMPTOMS

Calico symptoms on potato appear as pale to bright yellow or blotching of leaves. Some strains cause severe stunting and necrosis of stems and tubers. Dry, corky areas or rusty brown patches develop within tubers.

COMMENTS ON THE DISEASE

Alfalfa mosaic virus is transmitted by many species of aphids. Transmission of the virus is most likely to occur when aphids migrate into potato fields from nearby alfalfa or clover fields, the usual hosts for this virus. Infection often occurs on edges of fields located near alfalfa. Little or no secondary spread occurs within the potato field.

MANAGEMENT

Plant certified seed tubers and avoid planting near alfalfa or clover.

PUBLICATION

UC IPM Pest Management Guidelines: Potato
UC ANR Publication 3463
Diseases
R. M. Davis, Plant Pathology, UC Davis
J. Nuñez, UC Cooperative Extension, Kern Co.
B. J. Aegerter, UC Cooperative Extension, San Joaquin Co.
Acknowledgment for contributions to the disease section:
C. Smart, Plant Pathology, UC Davis

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