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Plum Pox Virus – General Fact Sheet

Plum pox is the most serious disease of plums, apricots and peaches in Europe. It is caused by the plum pox virus (PPV). Different strains of the virus occur with variable host susceptibility and symptoms. Yield and overall economic losses have been catastrophic to plum and peach growers in many countries.

Disease distribution

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). In October 1999, the D-strain of PPV was discovered on peaches grown in Adams County, Pennsylvania.

Host plants

PPV infects virtually all cultivated fruit tree species of the genus Prunus. Severe symptoms occur on apricot, plum, and peach trees. Almond trees may be infected occasionally but show few symptoms. Sweet and sour cherries are affected by only some strains of PPV. The strain reported in the United States does not affect cherries. The disease also affects some wild Prunus species, especially blackthorn (Prunus spinosa) which has been a natural source of infection in many countries.

Symptoms

Plum pox symptoms can vary greatly, making the disease difficult to recognize. Symptoms may appear on the leaves or fruits of infected trees. In some cases, only part of the infected tree or even only a single branch will show symptoms.

Symptoms are easiest to see in the spring when leaves show chlorotic spots, bands, or rings, vein clearing and even leaf deformation. Infected fruits show chlorotic spots or rings. Diseased plums and apricots may be deformed with internal browning of the flesh and pale rings or spots on the stones.

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 to highly susceptible hosts and watching for symptoms to develop.

Biology

The main source of plum pox is infected trees or budwood. The virus is spread in the field by several species of aphids. The aphids acquire the virus during feeding and then transmit it to nearby healthy plants. The aphids can only transmit PPV for a short period of time after acquiring it.

The virus can also survive in roots and may spread by natural root grafting. The suckers produced from the remaining roots of rogued infected trees often carry the virus and must be removed.

Long distance spread of PPV occurs through the movement and use of infected propagative materials (grafting and budding of infected material). Some strains of PPV can be transmitted through seed and pollen. PPV can not be spread by mechanical means such as pruning.

Control

Plum pox is a difficult disease to control. Once introduced it can quickly spread and become established in the native vegetation. Control of the virus requires regular surveys, removal of infected trees, and replacement with resistant varieties or non-host crops. There is no anti-virus treatment that can be applied to infected trees or orchards.

The use of disease-free propagative material at all times is crucial in preventing introduction to new areas.