How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS

A typical symptom of pepper plants affected with Alfalfa mosaic virus is a distinct yellow mosaic, or yellow discolorations on leaves. These symptoms are generally diagnostic for Alfalfa mosaic virus infections of peppers.

COMMENTS ON THE DISEASE

Alfalfa mosaic virus infections of peppers generally occur when peppers are grown near alfalfa fields. Alfalfa mosaic virus is seedborne in alfalfa and essentially all alfalfa fields can be considered infected. Alfalfa mosaic virus is transmitted by several species of aphids and spread from alfalfa to surrounding crops via aphids is common. Aphids transmit Alfalfa mosaic virus only while probing the leaf tissues. Once an aphid acquires Alfalfa mosaic virus, it retains the ability to transmit the virus for only a short period of time (minutes to hours) and spread is local and can be very rapid within fields. In general, field spread is related to overall aphid activity, not to the presence of colonizing aphids.

Alfalfa mosaic virus is the only virus in the alfamovirus group and has a wide host range among weed and crop plants.

MANAGEMENT

In general, Alfalfa mosaic virus is not a major problem in California peppers, although local Alfalfa mosaic virus infections occur each year. The best way to control Alfalfa mosaic virus is to avoid planting peppers near alfalfa fields. No resistance to Alfalfa mosaic virus is currently available in commercial pepper cultivars. No effective chemical control strategies are currently available. Insecticides aimed at controlling the aphid vectors are ineffective. They will not kill aphids before aphids transmit the virus to plants.

PUBLICATION

UC IPM Pest Management Guidelines: Peppers
UC ANR Publication 3460
Diseases
S. T. Koike, UC Cooperative Extension, Monterey County
R. M. Davis, Plant Pathology, UC Davis
K. V. Subbarao, USDA Research Station, Salinas
Acknowledgment for contributions to Diseases:
B. W. Falk, Plant Pathology, UC Davis

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