The Q&A Archives: Tobacco Mosaic Virus

Question: My tomatoe plants have been infected with TMV before. What exactly is this virus and how does it affect the tomatoe plant?

Answer: TMV is a very stable, persistent virus that is readily spread by human activities. Transplanting, tying, and pruning can effectively spread the virus. Infected leaf and root debris and seed are common sources of TMV. The virus can survive in plant debris for varying periods (up to 2 years under dry conditions), depending on soil moisture.

Symptoms of TMV first appear about 10 days after plants become infected. Symptoms appear as light and dark green mottled areas on leaves. Leaves on infected plants are often small, curled, and puckered. Plants infected early in their development are stunted and have a yellowish cast. Symptoms may vary depending on virus strain, time of infection, variety, and environmental conditions. In hot weather, symptoms may not be as obvious although plants remain infected.

Certain strains of TMV can cause dark, longitudinal streaks of varying lengths on stems. Affected stems are brittle and appear brown internally.

TMV can reduce size and number of fruit produced. The earlier a plant becomes infected, the greater the loss. Fruit usually do not show any malformation. Occasionally, mottling, bronzing, and internal browning of fruit occur. Internal browning is evident on mature but unripened fruit.

For even more detailed information about TMV, visit the following websites:

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