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Many viruses affect tomatoes causing mosaic patterns on leaves, leaf distortions, stunted growth, bronzing or marbling patterns on the fruit.
Tomato plants affected by virus show mosaic patterns on leaves. Image: RHS, Horticultural Science
More than 20 viruses affect tomatoes worldwide, causing a wide variety of mosaic patterns and distortions to the leaves, stunted growth and marbling patterns on the fruit, whenever the plants are growing from late winter until early autumn.
The most common tomato viruses are:
Pepino mosaic virus was first detected in Europe in 1999, and is controlled by plant health regulations.
For more on how these viruses are transmitted, see the Biology section below.
You may see the following symptoms:
Stunting, distortion and fern leaf may also be caused by exposure to hormone weedkillers, to which tomatoes are very sensitive. These are volatile and can act from a distance, without direct contact. Providing the source is removed, plants usually recover, but they do not usually recover from virus infection.
There are no chemical controls. The use of insecticides to reduce aphid transmission is not practical.
Plant viruses share many of the characteristics of those that infect animals, though they do not cross infect (plant viruses only infect plants). Viruses are extremely minute and consist of a protein coat and a core of nucleic acid. They have no means of self-dispersal, but rely on various vectors to transmit them from infected to healthy plants. Once viruses penetrate into the plant cells they take over the cells’ nucleic acid and protein synthesis systems and hijack them to produce more virus. They then require another vector to feed on the infected tissue and carry them to a new host.
Several of these viruses have other common garden host plants. CMV has a very wide range of hosts, not only among cucurbits. TMV also affects tobacco and potato. TSWV affects many plants in the tomato family (Solanaceae) and also gloxinias (Sinningia), arum lilies and dahlias.
PepMV was first detected in Europe in 1999. Although it is controlled by plant health regulations gardeners do not need to report suspected outbreaks, but should not save seed from affected plants for re-use. See the Defra Plant Health Portal for more information on symptoms.
A number of other non-indigenous viruses and viroids are a threat to tomato production in the UK. Details can be found in this Defra factsheet.
Cucumber mosaic virus
Disposing of diseased material
Potato and tomato blight
Tomatoes: leaf problems
Tomatoes: stem problems
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