Agriculture Reference
In-Depth Information
a pale colour and water-soaked. Base rot and butt rot of
pineapple plant are also caused by the same fungus
especially where drainage is poor.
Candida guilliermondii
, the pineapple fruit mite,
Steneotarsoneumu ananas
(Tryon), and the pineapple red
mite,
Dolichotetranychus floridanus
(Banks), are associated
with FCR (Rohrbach & Schmitt 1994; O'Donnell
et al
.
1998). The condition has been reported from all major
pineapple producing countries (Snowdon 1990), but it is spo-
radic (Pegg
et al
. 1995) and rarely occurs at epidemic levels.
Low-acid cultivars (Rohrbach & Schmitt 1994) and rough
leaf pineapples grown commercially are the more susceptible
than Smooth Cayenne (Pegg
et al
. 1995). The disease is more
common in fruit maturing during the winter or spring.
Both
P. funiculosum
and
F. guttiforme
are involved in
flower infections, but there is no cause-and-effect relationship
established for the yeast,
C. guilliermondii
. The importance
of
P. funiculosum
and
F. guttiforme
varies among different
production areas. In Brazil,
F. guttiforme
is the predominant
cause of FCR, whereas
P. funiculosum
is the most common
cause of FCR and LP in South Africa (Rohrbach 1980;
Rohrbach & Taniguchi 1984). In Hawaii, both
P. funiculosum
and
F. guttiforme
cause FCR symptoms, while only
P. funiculosum
causes IFC and LP (Rohrbach & Schmitt
2003).
P. funiculosum
was consistently isolated from
pineapple fruitlets with black spot symptoms.
The pineapple fruit mite,
S. ananas
Tryon associated
with the disease seems to enhance the pathogenesis of
P. funiculosum
but does not act as a vector (Rohrbach &
Apt 1986).
S. ananas
is light brown and the adult male is
oval with an average length of 0.2 mm and width of
0.10 mm (Petty 1975, 1978).
D. floridanus
is a large phy-
tophagous mite found on pineapple, and is conspicuous
because of its bright orange to red colour. The adult mite is
0.3-0.4 mm long and 0.1 mm wide (Petty 1975, 1978).
P. funiculosum
builds up on mite-damaged trichomes on
the basal parts of heart leaves, and on the bracts and sepals
of flowers. The fungus can also infect unopened flowers and
on developing flowers 1-2 weeks before anthesis (Pegg
e
t al
. 1995). On unopened flowers,
P. funiculosum
initially
causes necrosis of the anthers and pistil, blue green sporula-
tion on ovules and locule walls cork formation on the
locules. As the disease progresses, septa between locules
become dark to medium brown, and the discolouration may
extend into adjacent noncapillary tissues (Rohrbach &
Schmitt 2003). Further corking of locules as fruit matures
results in LP (Rohrbach & Schmitt 1994). LP disease was
formally attributed to mite damage (Le Grice & Mark 1970)
but it has now been established that
P. funiculosum
is the
primary cause (Lim & Rohrbach 1980). IFC develops on the
fruit surface between affected fruitlets which do not enlarge
rapidly as healthy fruitlets. This results in distortion of
affected fruitlets (Hepton & Anderson 1968).
Control
Black rot is commercially controlled in fresh fruit by
minimizing bruising of fruit during harvest and handling,
by refrigeration and with fungicides (Nakasone & Paull
1998). The fruit should be carefully handled to avoid
mechanical damage as invasion of the fungus can occur
through minute fractures. As sunburnt and damaged fruit
could have minor skin cracks that are readily infected,
these should be rejected. Susceptibility varies with the
cultivar, Red Spanish types being more resistant than
Smooth Cayenne (Rohrbach & Schmitt 1994; Nakasone &
Paull 1998). Removal of pineapple refuse and rejected fruit
in packing areas and at the market is important to reduce
inoculum and infection (Pegg
et al
. 1995).
The base of the fruit can be dipped in a recommended
fungicide within 4-5 hours of harvesting, especially for
fruit harvested during warm, wet weather (Pegg 1993).
Wax treatment at a post-harvest level has been proved
effective against the disease (Wijeratnam
et al
. 2006). Hot
water treatment at 54°C for 3 minutes controls disease
when stored at 10°C for 21 days followed by 48 h at
ambient temperature (28 ± 2°C) and also at 28 ± 2°C for 6
days (Wijeratnam
et al
. 2005).
Complete inhibition of spore germination of
C. paradoxa
has been observed with 2% acetic acid (AA) (v/v) and
radial mycelial growth of the organism showed inhibition
at 3% AA. Black rot of Mauritius (Queen) pineapples
was shown to be minimal after a 7-day storage period at
28 ± 2°C when fruits were subjected to a three minute dip
at either 4% or 5% AA (Wijeratnam
et al
. 2006).
The use of microbial antagonists as agents of biological
control, such as
Pichia guilliermondii
or a yeast mixture
has also proved to be successful. The use of
Pichia
or the
yeast mixture was comparable with current industry
practice of holding fruit at a low temperature (8-10°C) and
fungicide (Reyes
et al
. 2004).
Fruitlet core rot, leathery pocket
and interfruitlet corking
Fruitlet core rot (FCR), black spot, fruitlet brown rot and eye
rot are terms that have been used to describe brown to black
diseased centres of individual pineapple fruitlets. Leathery
pocket (LP) and interfruitlet corking (IFC) are additional
symptoms that develop as FCR continues to develop.
The fungi
Penicillium funiculosum
and
Fusarium
guttiforme
(formerly
Fusarium moniliforme
), the round yeast
