Plum Pox Virus Fact Sheet
Plum pox/sharka is a serious plant disease caused by Plum pox virus (PPV). The virus infects stone fruit species of the genus Prunus including peaches, nectarines, plums, apricots, cherries, almonds and ornamental species. PPV does not normally kill the host trees, but can drastically reduce yields and affect fruit quality. PPV is transmitted from infected trees by aphids or by grafting or budding. PPV does not affect human or animal health.Footnote 1
Plant pest card - Plum Pox Virus
First identified in Bulgaria, plum pox is now reported in most European countries, in parts of Asia and northern Africa, and in South America (Chile). The PPV-D (Dideron) strain of the virus was first detected in North America in the United States in 1999 in the state of Pennsylvania and in Canada in the provinces of Ontario and Nova Scotia in 2000.
There are several strains of PPV that infect different Prunus species including peach, plum, apricot, nectarine, cherry and almond trees. Ornamental species such as purple-leaf sandcherry and flowering almond can also be infected by PPV. Cherry trees can be infected by PPV, however, the strain reported in North America does not infect cherries. The virus also infects some wild Prunus species such as blackthorn (Prunus spinosa) which has been a natural host of the virus in some countries.Footnote 1
Symptoms of PPV may include chlorotic ring spots on leaves and fruit, fruit deformity, decrease in fruit yield as well as early fruit drop. The symptoms are easiest to detect in the spring.
Visual symptoms are not always a reliable indicator of disease. The disease may not be visible until several months or years after the tree has been infected. However, PPV can also be detected by laboratory analysis of tissue samples or by grafting test material onto highly susceptible hosts and monitoring for the development of symptoms.
The two main pathways by which PPV is spread are aphid feeding and propagation or multiplication of infected material. Propagation and multiplication activities include budding and grafting. PPV cannot be spread by mechanical means such as pruning.
Aphids acquire the virus during feeding and then spread it to healthy plants. Aphids can only transmit PPV for a short period of time after acquiring the virus.
The virus can survive in roots and may be spread by natural root grafting. Root suckers produced from the remaining roots of rogued infected trees may contain the virus and should be removed.
There is no treatment for PPV and once a tree has become infected the only way to prevent spread and destroy the virus is to remove the tree and its roots.
The use of virus-free propagative material at all times is crucial in preventing introduction to new areas.
Figure 1 - Chlorotic ring spots on fruit. Photo courtesy of Michael Celetti, Ontario Ministry of Agriculture, Food and Rural Affairs © Queen's Printer for Ontario, 2015. Reproduced with permission.
Figure 2 - Yellow lines and vein clearing symptoms on peach leaf. Photo courtesy of Michael Celetti, Ontario Ministry of Agriculture, Food and Rural Affairs © Queen's Printer for Ontario, 2015. Reproduced with permission.
Figure 3 - Cholortic ring spots on peach leaves. Photo courtesy of Michael Celetti, Ontario Ministry of Agriculture, Food and Rural Affairs © Queen's Printer for Ontario, 2015. Reproduced with permission.
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