- Sap
- Insects
- Nematodes
Sap
Viruses can be spread by direct transfer of sap by contact of a wounded plant with a healthy one. Such contact may occur during agricultural practices, as by damage caused by tools or hands, or naturally, as by an animal feeding on the plant. Generally TMV, potato viruses and cucumber mosaic viruses are transmitted via sap.
Insects
Plant viruses need to be transmitted by a vector, most often insects such as leafhoppers. The chosen insect vector of a plant virus will often be the determining factor in that virus's host range. Plant virus are classified as non-persistent, semi-persistent and persiste depending on the different ways of transmission by insects.
Green peach aphid Myzus persicae, the vector of many plant viruses, including Potato virus Y.
Hoppers transmit viruses from several genera.
Micrutalis malleifera, the treehopper vector of Tomato pseudo-curly top virus.
Nematodes
Soil-borne nematodes also have been shown to transmit viruses. They acquire and transmit them by feeding on infected roots. The virions attach to the stylet or to the gut when they feed on an infected plant and can then unattach during later feeding to infect other plants. Example of viruses that can be transmitted by nematodes includes tobacco rattle virus.
Adult female of Paratrichodorus pachydermus, the vector of Tobacco rattle virus.
