How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS

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.

COMMENTS ON THE DISEASES

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.

MANAGEMENT

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.

PUBLICATION

UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470
Diseases
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