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UC Pest Management Guidelines

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Citrus

Alternaria Rot

Pathogen: Alternaria citri

(Reviewed 7/03, updated 7/03)

In this Guideline:

Symptoms
Management

SYMPTOMS
Alternaria rot is a fungal disease that affects mainly navel oranges and lemons. Fruit infected with Alternaria change color prematurely. The decay is softer on lemons than on oranges and develops mostly during storage. On navel oranges, the disease is also called black rot, and results in dark brown to black, firm spots or areas at the stylar end or in the navel. If you cut the fruit in half, you can see the rot extending into the core.

MANAGEMENT
Healthy, good quality fruit are more resistant to Alternaria rot than stressed or damaged fruits, especially oranges with split navels. Preventing stress can reduce the incidence of splitting and Alternaria rot.

PUBLICATION

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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