Plum pox virus (Sharka)

  • Plum Pox leaf symptoms
    Plum Pox leaf symptoms
  • Leaf symptoms and discolouration of stone
    Leaf symptoms and discolouration of stone
  • Fruit symptoms of plum pox
    Fruit symptoms of plum pox

Have you seen plum pox symptoms?

In Queensland, Plum pox virus (sharka) is prohibited matter under the Biosecurity Act 2014.

Be on the lookout for symptoms and report them to Biosecurity Queensland on 13 25 23.

Early detection and reporting of symptoms are the key elements in controlling the pest.

Call us 13 25 23

General information

Plum pox (also known as Sharka) is the most destructive disease of stone fruit worldwide, and a major threat to the Queensland stone fruit industry. The virus infects all Prunus species, including the cultivated stone fruits (almonds, plums, peaches, nectarines, cherries and apricots) and ornamental of wild Prunus. It also affects a range of weed hosts such as white clover and nightshade.

Plum pox causes high yield losses and has resulted in large areas of tree removal wherever it is found. Plum pox is currently present in Europe, the Mediterranean, the Middle East (Egypt and Syria), India and South America (Argentina and Chile).

The virus was first detected in the north-eastern United States of America and Canada in 1999-2000, where a major eradication is still in place. Plum pox has not been detected in Australia or New Zealand.

Overview

What causes plum pox?

It is caused by the plum pox virus (PPV).

What does it look like?

A wide range of symptoms may be visible depending on the host variety, virus strain, plant age, time of year and temperature. Leaf symptoms are most likely on younger leaves in spring, and include chlorotic spots and blotches, vein banding, rings and line patterns. Infected fruit develop discoloured rings, spots, or bands on the skin (Figure 3). External pitting, grooving (Figure 4), or deformation of the fruit may also occur, as well as internal flesh discolouration and marking on the stone (Figure 5).

How does plum pox spread?

Aphids are small sucking insect pests that can spread the disease over short distances, such as in or between orchards. Many aphid species in Australia would be efficient plum pox vectors.

Long-distance spread and introduction of plum pox to new regions most frequently occurs via the movement of infected plants or plant parts. The discovery of plum pox virus in several European countries was associated with introduction of infected nursery stock. The Australian Quarantine and Inspection Service restricts the entry of stonefruit plants and plant material to Australia because of this risk.

What are the implications of an outbreak in Australia?

Plum pox is extremely damaging to fruit production. Tree yields can be severely affected and up to 100% premature fruit drop has been reported in some plum varieties. Infected fruit is unsightly and misshapen, and generally unmarketable.

Because of the seriousness of the disease, quarantine restrictions on movement of fruit and plant material would be likely in an outbreak to prevent further spread of the organism.

Controlling plum pox

Quarantine and certification
Plum pox is extremely difficult to eradicate from a growing district once it becomes established. Because the disease is easily spread on plant material, unaffected areas and districts can be protected through the implementation and enforcement of quarantines on movement of these items. Spread can also be controlled though the use of planting material that is certified free of plum pox.

Tree removal
Infected trees cannot be cured so, in a newly affected orchard, they are normally destroyed quickly to minimise spread. In France, where plum pox is well established, infected trees are removed within one week of the virus being detected.

Aphid control

Excessive spraying for aphid control in stonefruit orchards will not prevent plum pox spread. While insecticide applications will reduce total aphid populations in orchards, 100 per cent control of this insect is not possible, and it only takes one or two aphids to infect a tree.

Resistance

The ability to breed stonefruit cultivars that are resistant to plum pox holds the key to controlling this disease in the future. Some cultivars are known to be more tolerant but as yet none have been identified that are completely resistant to the disease. However, some promising work is occurring in this area in Europe.

Further information

If you need further information, contact the Customer Service Centre .

If you think you've seen plum pox, call the Exotic Plant Pest Hotline on 1800 084 881.

Last updated 11 July 2011