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Plum Pox Virus Fact Sheet

Background

Plum pox 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 propagation activities using infected host material. PPV does not affect human or animal health and is not a food safety risk.

Plant pest card - Plum pox virus

Distribution

First identified in Bulgaria, PPV is now reported in most European countries and in parts of Asia, northern Africa, South America and North America. In North America, the virus was first detected in the United States in 1999 in the state of Pennsylvania and, in 2000, in Canada in the provinces of Ontario and Nova Scotia. In 2017, PPV was reported in Mexico, although it is believed to have been present since 2005.Footnote 1 The virus has been successfully eradicated from the United States and from Nova Scotia, Canada, but is still considered present in the Niagara Region in Ontario, Canada, and in Mexico.Footnote 2

Among the different strains of PPV reported across the world, the Dideron strain (PPV-D) is the strain that was detected in Canada, Mexico and the United States. PPV-D is the only strain that remains present in North America (Hajizadeh et al 2019). Isolated detections of the Winona strain (PPV-W), and the Recombinant strain (PPV-REC) had been detected in Canada and are now considered eradicated.Footnote 3 Footnote 4

Host Plants

There are several strains of PPV that infect different Prunus species, including peach, plum, apricot, nectarine, cherry and almond trees. The strain present in North America (PPV-D) can infect many Prunus species; however, cherries are not naturally infected and are generally believed to be resistant to this strain.Footnote 2 Ornamental species such as purple-leaf sandcherry and flowering almond can also be infected by PPV. 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 5

Symptoms

Symptoms of PPV may include chlorotic ring spots on leaves and fruit, fruit deformity, decrease in fruit yield and early fruit drop. Symptoms are easiest to detect in the spring, but visual symptoms are not always a reliable indicator of disease, because they may not be visible until several months or years after the tree has been infected. PPV can be more reliably detected by laboratory analysis of tissue samples or by grafting test material onto highly susceptible hosts and monitoring for the development of symptoms.

Means of transmission

The two main pathways for PPV spread are aphid feeding and propagation of infected host material through activities such as budding and grafting. The virus can survive in roots and may be spread by natural root grafting. Root suckers produced from the remaining roots of removed infected trees may contain the virus.

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.

PPV cannot be spread by mechanical means such as pruning and is not transmitted by seed or pollen.Footnote 6

Control

There is no treatment for PPV. Once a tree has become infected, the only way to prevent spread and to destroy the virus is to remove the tree and its root system. 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 - Chlorotic 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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