How to Manage Pests
UC Pest Management Guidelines
Pathogen: Cucumber mosaic cucumovirus (CMV)
(Reviewed 12/09, updated 11/12)
In this Guideline:
SYMPTOMS AND SIGNS
Symptoms on plants 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, and mosaic, and mature leaves can develop necrotic areas shaped like oak leaves. 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 this virus and one or more of the potyviruses can simultaneously infect plants.
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 this virus 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.
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. Eliminating weeds and using reflective mulches to repel the insect vector may reduce the incidence of this disease.
Chemical pesticide strategies are not effective. Insecticides directed at controlling the aphid vectors are not effective in preventing this virus because they cannot kill the aphids before transmission occurs; however, growers should still attempt to manage vector populations when possible (for more information, see GREEN PEACH APHID).
UC IPM Pest Management Guidelines:
S. T. Koike, UC Cooperative Extension, Monterey County
Acknowledgment for contributions to Diseases:B. W. Falk, Plant Pathology, UC Davis