Plum pox potyvirus (PPV)
English names: Sharka, Plum pox
Nordic names: Blommpoxvirus (DK), Sharkavirus (NO), Sjarka-virus (SE)
Estonian name: Ploomirõuged, ploomi-sarkahaigus
Major host plants
Stone fruit trees (genus Prunus) such as plums (P. domestica and P. salicina), peach (P. persica), almonds (P. amygdalus) and cherries (P. avium and P. cerasus) are the natural hosts of PPV. Wild hosts are potential reservoirs of the disease.
Symptoms of PPV depend on the host species and age as well as the locality and the season. The severity of symptoms may differ according to the strain of the virus. General symptoms include early fruit drop, reduced sugar content, leaf symptoms and presence of spots on fruit and seeds. Symptoms often appear 3 years following initial infection and they are particularly clear on leaves in spring or early autumn.
- Leaves: pale green or light yellow chlorotic spots, blotches, rings or line patterns, which are often difficult to see in bright sunlight.
- Fruits: red or dark-colored fruits develop bluish, necrotic rings which may be sunken, while pink-skinned fruits show uneven ripening, blotching and rings together with pale rings or spots on the stones.
- Flowers: pink stripes on the flower petals, which can be useful for early season surveys.
- Leaves: yellow or banding patterns along the veins.
- Fruits: yellow or red rings/blotches on the skin. When rings run together, line patterns may be evident. Infected fruit can also be deformed and have spots on stones.
- Leaves: yellow or light green spots, vein yellowing, netting or blotches.
- Fruits: large yellow or red rings or line patterns. May become deformed or bumpy and develop brown patches. Distortion extends to pits. There may be white ring or line patterns on stones.
- Leaves: yellow rings or blotches.
- Fruits: notched marks and yellow or brown rings.
PPV originates from Eastern Europe (Bulgaria) and has spread from there to most of the continent. Until recently, no case had been reported from outside the EPPO Region, but PPV has now been found on other continents.
A map can be downloaded from EPPO’s website. See instructions here.
Infected Prunus trees are the major source of inoculum. The virus is transmitted to other potential hosts either by grafting or by aphid vectors. The disease develops slowly inside the tree, usually affecting only one or two branches at first, but spreads through the tree as the virus multiplies over a period of several years.
In cool climates aphid transmission is probably not very important due to the biology of the vectors. Aphids are changing hosts and are only found on Prunus during autumn and winter. In spring they migrate to herbaceous hosts and stay there during the summer period.
Types of PPV: There are six known strains of PPV: D, M, EA, C, W and PPV-Rec (Recombinant).
PPV-D and PPV-M are the most widely distributed strains of PPV and they infest plum, peach, nectarine and apricot. PPV-M is more aggressive and spreads rapidly in orchards via aphids.
Cherry is only infected by PPV-C.
Long-distance spread occurs by movement of infected nursery stock or propagative materials.
PPV is spread over short distances by several aphid species.
Detection and inspection
Visual inspection of trees, especially during the period of active growth, allows detection of PPV on the basis of symptoms. Sampling of trees can be difficult since the distribution of the virus in a tree can be irregular and some plant parts may have undetectable concentrations of the virus. For this reason, multiple samples must be obtained for laboratory testing from the suspected tree. The time of year when the sample is taken is critical and can greatly affect the test results. Optimal sampling time is during spring or early autumn, but it can vary from season to season depending on the weather conditions.
Pest status and importance
PPV is economically important because it can cause fruit to be unmarketable and can decrease the yield of infected trees. In the EPPO region, it presents a major risk to apricots, plums and peaches. In addition, its presence in a country creates difficulties for export of certified planting material.
Source of information
See further information here:
Author: Eigil De Neegaard and Elise T. Yamamoto Buch
Editor: Dorthe Vestergaard