This is an important point to remember when considering control of virus diseases. Even though symptoms may disappear temporarily, plants remain infected for life. Infected canes are usually short and less vigorous than healthy canes. Leaves are mottled with yellowish or light green spots on a darker green background. Leaves that develop in hot weather may be symptomless or show only faint mosaic pattern with yellow flecks in the normal green color.
Leaves formed in late summer show a fine, yellowish, speckled mottling.
Mosaic-infected plants are often progressively more stunted each year. On black and purple raspberries, the tops of newly-infected canes often curl downward, turn black, and die. The aphid is widespread and feeds on the undersides of leaves near the tip of the canes. The aphids become contaminated with the viruses and can spread the viruses to healthy plants up to a quarter of a mile or more away. The mosaic virus can also be spread by commercial propagation from infected plants and movement of the diseased nursery plants.