Tobacco Mosaic Virus

Infected plants typically show a mottled mosaic pattern of light and dark green (or yellow-green) patches on leaves, sometimes with leaf distortion, narrowing, or blistering, along with stunted growth and reduced yield. Symptom severity can vary considerably with plant variety, virus strain, and growing conditions, and symptoms can be masked at high temperatures.

TMV particles are unusually stable and resistant to degradation, which allows the virus to persist in dried plant material, cured tobacco products, contaminated soil, and on surfaces such as tools, stakes, and hands for extended periods. Infection occurs when the virus, present in sap or on a contaminated surface, is introduced into a plant through even minor wounds created during normal handling.

• Contaminated hands and tools during pruning, tying, or grafting are a major route of spread
• Contact with tobacco products can transfer the virus to susceptible crops such as tomato and pepper
• Low rates of seed transmission can occur through virus-contaminated seed coats
• Unlike many plant viruses, TMV is not significantly spread by insect vectors

Tobacco is the namesake host, but tomato and sweet pepper are also economically important hosts, along with numerous other cultivated and wild plants. Susceptibility and symptom severity vary by variety, and some tomato and pepper varieties carry resistance genes that reduce or prevent disease development.

• Frequent plant handling, such as pruning, tying, or grafting, without hygiene precautions
• Workers handling tobacco products before working with susceptible crops
• Reuse of contaminated stakes, ties, tools, or growing media between crops
• Use of seed or transplants from an infected source
• Susceptible varieties lacking resistance genes

Because there is no way to cure a plant once infected with TMV, and because the virus is so persistent in the environment, prevention centres on hygiene, resistant varieties, and removing sources of infection rather than reacting after symptoms appear.

• Choose resistant or tolerant varieties where available
• Wash hands and disinfect tools between plants, especially during pruning, tying, or grafting
• Avoid handling tobacco products before or while working with susceptible crops
• Use certified virus-free seed and transplants
• Remove and destroy infected plants and avoid reusing contaminated stakes or growing media