Agriculture Reference
In-Depth Information
Fruit: small, brown, circular spots rapidly increase in size
to involve the whole fruit. The colour becomes jet black
and the fruit shrivels to a mummified condition.
favourable conditions and may completely envelop the
fruit. Under warm, moist conditions, at first white then
pale blue and finally blue-green powdery clumps of
fungal spores develop on the surface of the spots. The
fruit eventually becomes a soft, watery mass with
a characteristic musty smell.
Fruit symptoms can be confused with bitter pit, a calcium
deficiency, in their early stages of development.
Source of infection and spread
The fungus survives in cankers and mummified apples on
trees. Spores from fruiting bodies in fruit mummies or
cankers are spread during wet weather by wind and rain.
Source of infection and spread
Fruit, soil and bulk bins are the major sources of blue
mould spores.
Fruit and soil: blue mould fungi infect damaged or fallen
fruit on the orchard fl oor. Spores develop on the surfaces
of these fruit, contaminate the soil and are blown by wind
throughout the orchard to fruit on the trees. During
harvest, contaminated soil travels with the fruit in bulk
bins to the packing shed and is loaded into fruit dumps,
dips or recirculating drench solutions.
Importance
The disease causes moderate losses in the cultivar Granny
Smith.
Management
Remove affected branches during pruning and destroy
mummifi ed fruit.
Reject fruit in the packing shed produce blue mould
spores that spread with dust onto the grading machinery
surfaces.
Broad-spectrum protectant fungicides used to control
apple black spot will also reduce losses from black rot.
BLUE MOULD
Cause
The fungi Penicillium expansum and P. verrucosum .
Symptoms
Both apple and pear are affected.
After harvest, the fruit initially develop soft, pale brown,
watery spots with the decayed portions sharply separated
from the healthy tissues. Spots enlarge rapidly under
Fig 3.18 Blue mould symptoms on pear. Inset: lesions extend to the
seed cavity.
Fig 3.17 Advanced symptoms of blue mould on pears.
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