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.
- CMV is vectored by aphids
- TSWV is vectored by thrips, especially the western flower thrips
- TMV is very easily spread mechanically on tools or fingers
- PepMV is mechanically transmitted, although seed transmission is possible
- TMV is occasionally transmitted through seed
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.