How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS

Symptoms on plants affected with cucumovirus mosaic diseases can vary, but in general, plants show an overall lighter color along with mosaic patterns (alternating light and dark green areas) on at least some leaves, especially on the younger leaves. Often, the main leaf vein is distorted and somewhat zigzag in appearance. Plants generally show stunting, leaf curling, mosaic, and oak leaf patterns. Fruit may be malformed and have conspicuous concentric rings or spots. It can be difficult to accurately differentiate plants affected by Cucumber mosaic cucumovirus from those affected by the potyviruses. In general, Cucumber mosaic cucumovirus infections are more severe than infections by the potyviruses. However, mixed infections are very common, and plants can be infected by Cucumber mosaic cucumovirus and one or more of the potyviruses.

COMMENTS ON THE DISEASE

Cucumber mosaic cucumovirus is spread from plant to plant by aphid vectors; many aphid species are competent vectors. Aphids transmit Cucumber mosaic cucumovirus while probing the leaf tissues. Once an aphid acquires Cucumber mosaic cucumovirus, it retains the ability to transmit the virus for only a short time (minutes to hours); the spread of the virus is thus local and very rapid within fields. In general, field spread is related to overall aphid activity, not to the presence of colonizing aphids.

Several strains or pathogenic variants of Cucumber mosaic cucumovirus exist. This virus has a tremendously wide host range among broadleaf crop and weed species and thus, eliminating alternate sources of inoculum is not a feasible management strategy.

MANAGEMENT

No good sources of Cucumber mosaic cucumovirus resistance in peppers are currently available. Efforts are under way to develop resistant cultivars, both through traditional plant breeding and with biotechnology.

Chemical pesticide strategies are not effective. Insecticides directed at controlling the aphid vectors are ineffective because they cannot kill the aphids before transmission occurs. Stylet oil formulations have proven effective in preventing aphid transmission of Cucumber mosaic cucumovirus in other locations, but have not been adequately tested in California.

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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