A strong cell wall boundary and immobility of plants necessitate the plant viruses to use vectors for the transmission to new host plants or to a new habitat. Virus retention sites within vectors vary depending on type of virus, vector and transmission modes. Viruses that are transmitted in a non-persistent manner are retained in the stylet, while viruses transmitted in a persistent manner are circulative non-propagative or circulative-propagative, i.e., they move with plant sap into the vector gut, from the gut lumen into the hemolymph or other tissues and finally back into the salivary glands from which they are introduced back into the plant during insect feeding or even can pass directly through the sheath of the filter chamber and be readily transmitted to healthy plants.