Once the plant is infected with the virus, the entire plant will be infected for the remainder of its life. Virus infections cause decreased productivity, so it is important to start a planting with healthy plant stock obtained from a reputable nursery.
Clean planting stock usually is obtained through meristem-tip culturing. Meristem-tip culturing produces an essentially virus-free plant. These indexing methods vary with the type of virus to be detected. The virus-indexed plants then are used to propagate more plants to commercial quantities. For the plants to remain essentially disease free, they must not be increased in the field where viruses and other pathogens can infect the plant. These propagation methods also reduce the likelihood of other diseases such as crown gall.
Once the planting is established, viruses can be introduced into the planting by various means. The virus must be carried to the raspberry bushes by a vector. The vectors responsible for spreading viruses are pollen, aphids, nematodes, and possibly leafhoppers and whiteflies. Thus, the active control of virus diseases is based on preventing the initial infection of clean stock by removing sources of virus near the planting, mainly wild bramble bushes, and by controlling the vectors. If a young planting shows virus symptoms, the planting stock probably was infected at the time of planting since symptoms do not usually appear during the first season of infection.
Five major virus diseases are associated with brambles: mosaic, leaf curl, crumbly berry, black raspberry streak, and tomato ringspot virus.