Plant viruses are extremely minute infectious particles consisting of a protein coat and a core of nucleic acid. They have no means of self-dispersal, but rely on various vectors (including humans) 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.
Viruses are frequently transmitted through propagated material but, depending on the virus, can also be transmitted via insect or mite vectors, pollen, mechanical transfer via contaminated hands and tools, or nematode vectors in the soil. Some viruses can be transmitted via seed, but generally these are a minority and therefore with many plants seed propagation is often a useful way to ensure virus free plant material.
Raspberry viruses are transmitted in a number of ways:
The large raspberry aphid (Amphorophora idaei) transmits Black raspberry necrosis virus, Raspberry latent virus (presence in UK unknown), Raspberry leaf mottle virus, and Rubus yellow net virus.
The small raspberry aphid (Aphis idaei) transmits Raspberry vein chlorosis virus.
The Raspberry leaf and bud mite (Phyllocoptes gracilis) transmits Raspberry leaf blotch virus.
Transmission of Raspberry chlorotic mottle virus is still to be determined, but may be by various insects, by pollen and by seed.
Raspberry bushy dwarf virus is pollen and seed transmitted.
Arabis mosaic virus, Raspberry ringspot virus and Strawberry latent ringspot virus are transmitted by soil-dwelling nematodes and by seed. Raspberry ringspot virus is also pollen transmitted.
Some of these viruses can also be transmitted on tools and hands.