Pineapple - Crop Post-Harvest: Science and Technology - page 149

F. guttiforme causes a light to dark brown discolouration
of septa that may extend down the entire fruitlet core.
White to pinkish mycelium and sporulation of the pathogen
occur in locules. The optimum temperature for infection is
16-20°C and temperatures higher than 20°C inhibit
disease development. Rainfall is needed for the fungus to
build up in damaged leaf hairs, but not needed for infection
to occur (Rohrbach & Taniguchi 1984). F. guttiforme
enters the fruit through open flowers or injuries on the
fruit. The risk of FCR due to F. guttiforme is higher when
flowers are initiated and fruit mature under warm
conditions (21-27°C) (Pegg et al . 1995).
The degree to which these symptoms develop appears to
depend on the time of infection, the pathogen or mixture of
pathogens that is present, the cultivar and the environmental
conditions (Rohrbach & Schmitt 1994). Smooth Cayenne
fruits do not show any external symptoms, therefore the
disease is undetectable. However, the Queen group may
produce fruitlets which fail to colour, a condition often
referred to as 'green eye'.
A global analysis of the data showed that average ascorbic
acid content in fruits at harvest is negatively linked with the
percentage fruits affected with FCR ( P. funiculosum ). The
nutritional status of the plants, especially low levels of
calcium and magnesium, and/or high levels of nitrogen and
climatic conditions before harvest are significant factors that
favour the development of the disease (Marie et al . 2000).

with no visible symptoms will be harvested and sent to the
market, where breakdown will become evident. When
conditions favour development of the disease, samples of
fresh market fruit should be cut and examined carefully for
internal rotting. As the disease progresses, a general,
water-soaked rot of green fruit with a distinct brown margin
develops (Pegg et al . 1995).

Control
Green fruit rot is primarily controlled through application
of registered fungicides for root and heart rot control.

Pink disease
Pink disease of pineapple fruit is characterized by the
brownish-pink pigmentation of the fruit tissue when heated
during canning (Rohrbach & Pfeiffer 1976). The disease
may be caused by strains of Erwinia herbicola , Glucon-
obacter oxydans , Acetobacter aceti and Pantoea citrea .
Depending on the species and strains involved and the
severity of infection, browning symptoms may appear in
the fruit flesh before cooking (Rohrbach and Pfeiffer 1976),
or a pinkish discolouration and wilted appearance may be
detectable in the whole fruit in the field before harvest
(Rohrbach 1989). This causes losses to fresh pineapple.
Most often affected fruits do not show any external
symptoms even when fully ripe. Internally the flesh may be
water-soaked or light pink (Plate 7.2) and have an aromatic
odour (may smell like cantaloupe melons), but none of
these symptoms may be immediately obvious. In some fruit,
only one or a few fruitlets may be infected. In highly trans-
lucent, low-sugar fruit the entire cylinder can be invaded
(Pegg et al . 1995). The production of 2,5-diketogluconate
by P. citrea appears to be responsible for the dark colour
characteristic of the pink disease in pineapple (Pujol &
Kado 2000). The fruit can be infected by certain strains
without producing symptoms, and the discolouration
occurs only when the fruit is sterilized, causing problems in
the canning industry (Rohrbach & Pfeiffer 1976). The
disease is therefore of considerable importance in process-
ing, where great care is needed to ensure that infected tissue
does not enter the canned product.
The disease has been encountered in Hawaii, the
Philippines, Australia and Mexico (Snowdon 1990). The
incidence of pink disease is usually low. Outbreaks in
Australia are very infrequent and scattered, often affecting
only one or two flushes of fruit on just a few properties.
Occasional economically significant epidemics have been
reported in Hawaii and Taiwan from February to April and
in the Philippines from August to September (Hine 1976;
Rohrbach & Schmitt 1994).

Control
Fungicides have not been effective except when applied
directly into the opening of the terminal leaves that is
created by the emerging inflorescence. No control measures
for fruitlet core rot caused by F. guttiforme have been
developed (Rohrbach & Schmitt 2003). Miticide sprays
help disease control. Integrated control with the pink
pineapple mealybug, D. brevipes , the pineapple fruit mite,
S. ananas and a fungicide application programme, from
one week before to 11 weeks after flower induction
controls the disease and allows 14 days storage at ambient
temperature (Petty et al . 2006). The sporadic nature of this
disease makes chemical control impractical and unecon-
omical in Queensland, Australia (Pegg et al . 1995).

Green fruit rot
Green fruit rot is caused by Phytophthora cinnamomi .
Serious losses generally follow heavy rains when phytoph-
thora root rot has caused plants to lodge (Pegg et al . 1995).
Green fruit in contact with the soil are liable to be infected.
Initially a water-soaked rot develops behind affected fruitlets,
with no external symptoms. There is a risk that infected fruit