Lemon and Lime - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 372

Table 20.6. Postharvest diseases of citrus produce.

Disease Cause Symptoms Occurrence Control

Blue and
green mold

Penicillium
italicum
P. digitatum

A softening of the
tissue followed by
development of a
water soaked
area.
Infection site
develops into a
white fungal
growth which
turns blue or
green as spores
are produced
White margin
(10-20 mm) with
green mold.

Citrus fruits in all production
areas. Optimum growth at
27 ◦ C. No growth above
30 ◦ C and slow below 10 ◦ C.

Careful handling of
fruit during and
after harvesting.
Fungicide should
be applied within
24 hours of harvest
and fruit washed
prior to fungicide
application. All
mouldy fruit should
beremovedinand
around the packing
shed.

Stem-end rots Diplodia

natalensis
Phomopsis citri
Collectotricum
glocosporioides

Key lime and common in
humid areas.

Proper sanitation of
packing line
equipment and use
of postharvest
fungicides.

Sour rot Geotrichum

candidum

A soft watery decay
around an injured
sectioninthe
rind. The decayed
area has a
well-defined ridge
around the margin
and produces
white slimy
spores.

Affects lemons during
long-term storage,
especially during warm
seasons. Favoured by high
temperatures and
humidities, optimum
growth at 30 ◦ C.

Careful handling of
fruit to reduce rind
damage. Fruit to be
treated with
fungicide that
controls sour rot.

Phytophthora
brown rot

Phytophthora
citrophthora or
P . parasitica.

Asoftleathery
brown rot on the
fruit rind with a
pungent odor.

Occurs in California
following cool, wet
weather, can be controlled
by heat treatment.

Copper fungicides
appliedtolower
parts of the tree.
Skirting the tree
reduces the chance
of fruit and foliage
coming into contact
with spores in rain
splash.

Alternaria
stem-end rot

Alternaria citri Follows senescence of the

calyx of the fruit.

Sources: Adapted from Kader (2002); Hardy (2004).