Agriculture Reference
In-Depth Information
Fig 6.41 Sooty mould on fruit. The superficial mould can be easily
rubbed from the surface.
Source of infection and spread
The fungi causing sooty mould are not parasitic but
entirely superficial saprophytes and live on the honeydew
secretions of scale insects and aphids.
Fig 6.42 Sour rot on lemon.
seasons and is favoured by temperatures of 25-30
C.
Mature fruit is highly susceptible, particularly when
stored for long periods.
°
Importance
The disease is minor if scale insects and aphids are well
controlled.
Importance
Sour rot is a major postharvest disease, particularly during
wet seasons.
Management
•
Use the recommended spray program for insect pests.
Management
•
Use recommended registered postharvest fungicides.
SOUR ROT
■
Handle fruit carefully to avoid damaging the skin.
•
Cause
The fungus
Geotrichum candidum
.
Pre-cool fruit to 10°C before transport.
•
Avoid long periods of storage and 'ageing' of late-season
fruit.
•
Symptoms
Sour rot usually occurs as a pale, very soft, watery decay of
ripe fruit in storage. Affected fruit have a putrid smell and
larvae of ferment f flies are commonly found in the rotting
tissues. White fungal growth is often produced on the
surface of these fruit.
Maintain good hygiene in the orchard and packing shed
to reduce contamination.
•
STEM-END ROT
■
Cause
The fungi
Diaporthe citri
and
Diplodia
spp.
Source of infection and spread
The fungus is a common soil inhabitant and is wind-
borne or splashed onto fruit in the field. Infection can
also occur from dirt and debris in dip tanks or drenches
in the packing shed. The fungus infects fruit through
injuries to the skin or, in storage, by contact causing
'nests' of rotting fruit. Sour rot is more severe in wet
Symptoms
Stem-end rot is a firm, tan-coloured rot beginning at the
stem end and spreading slowly through the fruit. The
causal fungi rarely develop visibly on the skin. The margin
