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UC Pest Management Guidelines

Mottling of tomato leaves due to tobacco mosaic virus.


Tobacco Mosaic Tobamoviruses

Pathogens: Various Tobamoviruses including Tobacco mosaic virus and Tomato mosaic virus

(Reviewed 1/08, updated 1/08)

In this Guideline:


Symptoms on tomato plants infected with Tobacco mosaic virus vary with the cultivar and the specific virus or strain. A mild mosaic develops on leaves with some leaf malformation, including a fernlike appearance. During cool weather shoestringlike symptoms appear on leaves, which is also characteristic of Cucumber mosaic virus in tomato. Necrotic patterns may develop on fruit.


These viruses are commonly encountered in transplants or fresh market tomatoes where the plants are trained or handled by workers because the viruses are easily mechanically transmitted. There are many sources of these viruses, including tobacco products, tomato seed, infected plant debris, and equipment; the tobamoviruses are not transmitted by insect, nematode or fungal vectors. The tobamoviruses are very stable viruses and can survive in plant debris for a number of years. These viruses are seldom seen in direct-seed fields.


Use seed that has been treated to eliminate seedborne inoculum. Extreme sanitation is needed. The disease is difficult to control if the plants have to be handled. Some cultivars have genetic resistance to specific tomato-infecting tobamoviruses.


[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470
R. M. Davis, Plant Pathology, UC Davis
G. Miyao, UC Cooperative Extension, Solano/Yolo counties
K. Subbarao, USDA Agricultural Research Station, Salinas
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center, Parlier
Acknowledgments for contributions to the disease section:
B. W. Falk, Plant Pathology, UC Davis

Statewide IPM Program, Agriculture and Natural Resources, University of California
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