Plum pox virus (PPV), also known as “sharka,” is one of the most devastating diseases of stone fruits (plums, apricots, peaches, nectarines, almonds, and cherries). There are at least four strains of the disease. The D strain, which had been detected in the U.S., does not appear to infect cherry species.
PPV is vectored by several aphid species. PPV is carried on the aphid’s mouthparts and may stay viable for approximately one hour, sufficient time for the aphid to transmit PPV up to 120 meters from the initial site of infection. Signs of disease may appear on leaves, flowers, and fruit. (See full-color fact sheet.) Diseased fruit may be distorted and show a characteristic ring or spot blemish. Although PPV does not kill trees, it can cause yield reduction and decreased fruit quality.
What You Should Know About Plum Pox Virus (Sharka)
- Plum pox (potyvirus, D strain) is a viral disease of stone fruit, including almonds, apricots, sweet and sour cherries, nectarines, peaches, and plums. It disfigures fruit and kills the host tree. Infected fruit becomes unmarketable. Infected trees produce less fruit. It can cause 80 to 100% yield losses.
- Plum pox is commonly known throughout the world as sharka disease.
- The disease has been found in Ontario and Nova Scotia, Canada. In 1999, it was discovered for the first time in the United States in Adams County, Pennsylvania. After three years of negative survey data the quarantined areas were declared disease free. Lifting the quarantine now means growers can replant peach, plum, nectarine and apricots.
Q: What are the symptoms of plum pox virus infection?
- Plum pox can infect the leaves, flowers, fruit, and seed.
- The symptoms and the severity of the disease depend on the strain of the virus, the type of stone fruit, the season, and the environment. Symptoms may be present, absent, or dormant.
- Infected leaves and fruit typically produce yellow and/or brownish rings. These yellow and brown colors may also form bands, streaks, or blotchy patterns, commonly described as mottled or mosaic.
- Infected plums often develop irregular, curled, and/or puckered fruit, while yellowish (chlorotic) rings may develop on the stones (pit).
- Symptoms on infected peach flowers are described as “color breaking,” where the color of the flower is not uniform, but blotchy or streaky.
Q: What should be done when plum pox virus is suspected?
- A grower who identifies a potentially infected stone fruit tree should contact the local county extension office for information on how the tree should be handled to get a positive disease identification and prevent disease spread.