By Barbara Fahs, Garden Guides Contributor
diseased plants

About Viruses

Just as the common cold is a virus that attacks humans, plant viruses are similar pathogens that attack plants. A common virus that home gardeners often encounter is the tobacco mosaic virus - it can decimate your tomatoes if they get infected.

Prevention and Control

With tomato tobacco mosaic virus, it is important not to allow the smoking of cigarettes near your garden. If you are a smoker, wash your hands after smoking and before touching your tomato plants.

Affected Plants

Viruses are specific to their host plant, which includes tomatoes, lettuce, cauliflower, lilies, ranunculus, roses and a long list of others. Over 400 plant viruses are known to exist.


The visible symptoms of a virus can include speckled or yellowing leaves, leading to eventual death. Some viruses, such as the "mosaic" viruses, cause a mottled appearance of the plant's leaves.

Predator Insects

Although insects do not consume viruses, they can spread them. Leafhoppers, nematodes and white flies are often the culprits in transmitting a plant virus to the host plant. Controlling such insects can help to control viruses.

Natural Controls

Chemical products do not control plant viruses. If you keep insect pests under control, those responsible for spreading a virus will not be able to do so. If you grow varieties of plants that are resistant to viruses, this helps to prevent problems later. Use virus-free planting material for crops such as potatoes.

Other Methods of Control

Monocropping, the practice of growing large numbers of just one plant, can increase the likelihood of a virus being introduced.

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