Central Science Laboratory, Harpenden, British Crown, Bugwood.org
Symptoms of raspberry mosaic vary with the raspberry variety, the type of virus infection, and the time of year. In general, symptoms might include delayed leafing out, dieback of shoot tips, and stunted canes or clusters of shoots from the same node. Plants usually die in a few years. Mottling or yellowish spotting and cupping or blistering of the leaves are common symptoms most easily seen in the early spring when the new leaves are expanding. Leaf symptoms often disappear during hot weather later in the season. Red raspberries are not as severely affected as black ones, but they still suffer reduced plant vigor and yield. Care must be taken in diagnosis since these symptoms can be mimicked by late spring frosts, powdery mildew, mite injury, fungicide and herbicide sprays, and boron deficiency.
The mosaic virus complex overwinters in infected plants and is spread by aphids. Feeding time needed to transmit viruses in the complex is only a few minutes. Standard control practices of establishing plants as far as possible from wild or older populations of brambles and using planting stock propagated from virus-free plants are useful. Controlling aphids may assist in slowing the spread of viruses within the planting; however, because the viruses are transmitted very quickly, it is unlikely that transmission can be thwarted. Of purple and black raspberries, Black Hawk, Bristol, and New Logan are tolerant; Cumberland is very susceptible. Canby, Reveille, and Titan, red raspberries are reportedly resistant because aphid vectors avoid them; most other red raspberry varieties are susceptible. Aphid vectors also avoid Royalty.