October Pest of the Month: Plum pox virus (PPV)

Name: Sharka, Plum pox virus (PPV)

Plum pox virus is one of the most destructive disease of stone fruit worldwide and is a major threat to the Australian stone fruit industry. Currently found in Europe, North America, South America and Asia; it is not present in Australia.

Symptoms:

The symptoms of Plum pox are variable. They can be expressed unpredictably and may be confused with other disorders such as nutrient deficiencies or injury caused by pesticides.

Symptom expression varies depending on host, cultivar, strain (of PPV), the age of the infected tree and the prevailing environment. May occur in only a few leaves or fruit, along one limb, or throughout the entire tree.

Symptoms could occur on:

  • Leaves – spring growth can exhibit yellow spots, bands or rings and vein clearing.
  • Fruit – can develop discoloured rings, spots, or bands on the skin. External pitting, grooving, or deformation of the fruit may also occur, as well as internal flesh discolouration.  With apricots marking may occur on seed shell.

Transmission:

The virus is transmitted from infected trees either by grafting or, non-persistently, by aphid vectors. Plum pox may be transmitted by many aphid species including the green peach aphid (Myzus persicae).

These 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 vectors of this virus.

Aphids can acquire the virus while feeding for as little as 30 seconds while transmitting the virus over 1-3 hours; only one aphid is required for infection.

There are multiple strains of Plum pox virus and at least one is seed transmitted.

Favoured by: Infected host material and aphids

Host range:

The virus infects all Prunus species, including the cultivated stone fruits including plums, peaches, nectarines, cherries, apricots and almonds, as well as wild species of Prunus and other ornamentals. It also affects a range of weed hosts such as white clover and nightshade. The natural host range of plum pox is the genus Prunus.

Virus isolates vary in their expression in different hosts and not all strains or isolates infect the same host range.

For further information, please refer to the Pest ID Tool at: pestid.com.au/sharka-plum-pox-virus

Note that the Pest ID tool is now available with free access to industry.

An initiative of the Nursery Levy funded National Nursery Industry Biosecurity Program (NY15004) and ‘Building the resilience and on-farm biosecurity capacity of the Australian production nursery industry’ Project (NY15002).