How to Manage Pests
UC Pest Management Guidelines
Potyvirus Mosaic Diseases
Pathogens: Pepper mottle potyvirus (PepMoV), Tobacco etch potyvirus (TEV), and Potato Y potyvirus (PVY)
(Reviewed 12/09, updated 12/09)
In this Guideline:
SYMPTOMS AND SIGNS
Symptoms on plants with potyvirus 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. Plants will often show stunting, leaf curling, and fruit distortion along with the mosaic pattern on leaves. Symptoms may be similar to those caused by cucumber mosaic virus.
COMMENTS ON THE DISEASE
All of the potyviruses affecting pepper are transmitted from plant to plant by several species of aphids. Aphids are able to transmit these viruses for very short periods of time (minutes to a few hours). The type of aphid activity that promotes virus spread occurs when aphids are actively moving through the pepper crop and are probing the plant tissues before they begin feeding. Once aphids colonize plants, settling down to feed, transmission is greatly reduced. Thus, spread is often very rapid. In general, field spread of potyviruses occurs when aphid activity in fields is high.
All of the potyviruses that affect peppers have wide host ranges that include other crops and many weed species, particularly those within the Solanaceae (tomato, potato, eggplant, and nightshade family). Various strains of the potyviruses exist, some of which differ in their specific pathogenicities. It is very common to find plants simultaneously infected by more than one of the pepper potyviruses and also by cucumber mosaic virus. While spraying for the aphid vector will not prevent virus infections from occurring, growers should still attempt to manage vector populations when possible.
Some resistance, derived from various plant species closely related to peppers, is currently available and efforts are under way to develop more resistant varieties. In general, sources of genetic resistance in bell types is greater for Potato Y potyvirus, followed by Tobacco etch potyvirus, followed by Pepper mottle potyvirus.
No effective chemical control practices have been developed for potyvirus mosaic diseases in California. The incidence of these viruses is unpredictable between years and locations. Insecticides are not effective in controlling the spread of these viruses because they do not kill aphids before the aphids can acquire and transmit the viruses to plants.
Silver reflective plastic mulches applied at planting have been shown to be effective in repelling aphids from plants, thereby reducing or delaying virus infection.
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