When the mouthpart of the aphids reaches these vessels, it is capable of taking up the virus. This process will take at least 6 hours. Before the virus can be transmitted by aphids to other plants, the virus has to travel through the aphid's body to the salivary gland. The selective uptake of the virus strains from the hindgut into the body fluid and salivary gland accounts for the preferential transmission of the virus strains by the aphids. This process can take up to 4 days.
Transmission takes place when virus-infected aphids penetrate the plant with their mouthparts.
To enhance penetration, aphids excrete saliva from the salivary canal to soften the tissue. By doing so, the virus is transmitted into the plant. When the virus is transmitted into a cell other than the phloem cells, the virus can multiply but no systemic infection takes place. Only when the virus is released into the phloem can a systemic infection take place and the disease develop. BYDV is not transmitted to the offspring of the aphids.