Cause Prune dwarf virus (PDV) is transmitted easily by budding and grafting. It also spreads naturally in the orchard by infected pollen. Thus, there is little spread until trees are old enough to bloom. Spread in sweet cherry is much slower than in sour cherry. Due to pollen transmission, a high percentage of the seeds may carry the virus.
Symptoms Early descriptions of symptoms were of trees infected with contaminating viruses such as Prunus necrotic ringspot virus and Green ring mottle virus. Leaf yellowing may appear the first year the tree is infected, but usually symptoms do not develop for several years. Symptom expression is most favorable about 2 weeks after night temperatures of 50°F to 60°F and day temperatures of 86°F to 95°F. Affected foliage is a green and yellow mottle with the green along the midrib and larger veins. These leaves drop, and a second or third wave of symptoms may occur. Eventually, 30% to 50% of the leaves may drop. Fruiting spurs are reduced so that infected trees develop a willowy growth habit with long bare branches. Yield is high quality but may be reduced by 50%. Tree decline is accelerated in the presence of Prunus necrotic ringspot virus.
- Use nursery stock that has been tested and found to be free of all known viruses.
- If propagating your own trees, use both virus-indexed budwood and virus-certified rootstock.
- Do not introduce infected pollen into healthy orchards during pollination.
- Establish new plantings in blocks, the larger the better, and preferably at some distance from older orchards.
- Rogue infected trees in new virus-indexed orchards, but it is not economical to rogue or replant mature infected orchards.
- Thermotherapy (24 to 32 days at 38°C) and/or apical meristem culture have been used to eliminate various viruses.
Reference Pallas, V., Aparicio, F., Herranz, M.C., Amari, K., Sanchez-Pina, M.A., Myrta, A., and Sanchez-Navarro, J.A. 2012. Ilarviruses of Prunus spp.: A continued concern for fruit trees. Phytopathology 102:1108-1120.