STONE FRUIT - Diseases of Fruit Crops in Australia - page 237

still appear if the other virus is introduced in the field during
insect pollination. However, this spread is usually slow.

Management
•

Remove infected trees.

Use only virus-tested scion material and propagate on
either virus-free rootstock clones or seedlings obtained
from virus-tested trees.

•

Importance
This disease is serious causing severe stunting and yield
losses in susceptible cultivars.

PLUM POX (SHARKA) DISEASE - BIOSECURITY THREAT

Plum pox is the most devastating viral disease of stone
fruit worldwide and is a major threat to the Australian
stone fruit industry.

Cause
Plum pox virus (PPV) (Potyvirus).

Host plants and importance
PPV infects Prunus species in family Rosaceae. Host plants
include apricots, peaches, plums, cherries, nectarines,
almonds and ornamental and wild Prunus species.

PPV was first described on plums in Bulgaria in 1915 and
has spread to a large part of Europe, the Mediterranean,
the Middle East (Egypt, Syria), India, South America
(Argentina, Chile). The virus was first detected in the
north-eastern United States and Canada in 1999-2000,
where a major eradication program is in place.
The virus has not been detected in Australia or
New Zealand.

Fig 17.31 Ring patterns on plum fruit caused by Plum pox virus .

Plum pox can result in major economic losses through
unmarketable fruit and yield decline.

Symptoms
The symptoms produced on infected plants vary
considerably according to cultivar, virus strain, plant
age, time of year and temperature.

Symptoms can develop on leaves and fruits of infected
plants. Leaf symptoms are most likely to occur on
younger leaves in spring when a range of symptoms,
including chlorotic spots and blotches, vein banding,
rings and line patterns, may develop.

Infected fruit develop chlorotic spots, rings or line
patterns. Plum and apricot fruit can be severely distorted
and bumpy with internal browning of the f flesh and rings
on the stone. Symptoms may not be present on all
branches of a tree nor on all leaves of individual
branches. Trees may be infected for one or more years
before symptoms are seen.

Fig 17.30 Apricot fruit showing internal decay caused by Plum
pox virus .