Agriculture Reference
In-Depth Information
• Removal of litter
• Removal of mature fruits before the new crop set, to pre-
vent pycnidial inoculum getting washed down (Ayres
2001).
(APPPC) and African countries (IAPSC/CPI). The disease
could establish and cause significant losses if introduced
into the European and Mediterranean citrus growing areas
and has recently been reported in the United States (EPPO
2009).
Chemical control
Once detected, an effective chemical control programme is
required. Spraying with protective copper compounds or
systemic fungicides (especially the benzimidazoles) can
protect the newly formed fruit. Although field fungicide
spray applications reduce the disease incidence to sustain-
able levels it does not eradicate quiescent infections, even
at low harvest incidence (Agostini
et al
. 2006). Other pro-
cedures that might aid in disease control include:
MINOR DECAYS
Aspergillus rot
Aspergillus rot is caused by
Aspergillus niger
van Tiegh
and usually occurs on fruit that has been left in the sun for
several days, fruit that was not cooled after picking or that
was held in storage at high temperatures (Eckert & Eaks
1989; Timmer
et al
. 2000).
• Early harvesting particularly to prevent late seasonal
infection.
• Controlling weeds between the rows with post-emer-
gence herbicides before blooming in order to cover the
infected fallen leaves with mulch.
• Mulching and removal of litter.
• Irrigation of the groves in the dry months to avoid exces-
sive fall of leaves and the predisposition of the plants to
be attacked by the fungus.
• Installing windbreaks in the groves to minimize the dis-
semination of fungus ascospores.
Symptomology
This fungus is usually present on fruit stored at relative
high temperatures (27-32°C), and does not decay fruit held
at temperatures lower than 20°C. Peel decay first appears
light coloured and soft and can easily be punctured
(Eckert & Eaks 1989; Timmer
et al
. 2000). This early
symptom can easily be mistaken for blue mould or sour rot,
but the decaying area becomes sunken, darker and covered
in masses of black spores (Klotz 1973).
Control
Specific control recommendations are not necessary for
A. niger
since it only occurs on fruit that are stored in the
sun for several days after harvest. Aspergillus rot can easily
be controlled by storing fruit at or below 15°C and by using
benzimidazole fungicides or imazalil (Timmer
et al
. 2000).
Storage and shipment of fruit in the dark at cool tem-
peratures decrease symptom development and will reduce
the amount of fruit discarded at the destination. Post-
harvest fungicide treatments are not considered effective
(Agostini
et al
. 2006). An alternative post-harvest treat-
ment using chitosan exhibited antifungal effects against
G. citricarpa
and also the potential to control the develop-
ment of black spot lesions on 'Valencia' oranges by stimu-
lating defence responses in the citrus skin (Rappussi
et al
.
2009). The search for further alternative post-harvest treat-
ments resulted in effective control of
G. citricarpa
with
the following potential agents:
Lentinula edodes
(Shitake
mushroom),
Agaricus blazei
(medicinal mushroom) and
Saccharomyces cerevisiae
(Pascholati
et al
. 2007).
Pleospora rot
Pleospora rot caused by
Pleospora herbarum
(Pers.:Fr.)
Rabenh. is reported as a minor fruit disease in several citrus
production areas (Eckert & Eaks 1989; Timmer
et al
. 2000).
Symptomology
Pleaspora herbarum
enters the fruit either at a wounded
site or at the stem end (Klotz 1973). Initially the affected
tissue remains firm but later becomes leathery. Decayed
fruit are dark brown to black internally and externally
(Timmer
et al
. 2000).
Phytosanitary risk
Guignardia citricarpa
has been added to the quarantine list
of the European and Mediterranean Plant Protection
Organization (EPPO). It is an A1 quarantine pest (not pre-
sent in that area) for Caribbean countries (CPPC) and an
A2 quarantine pest (present in that area but not widely dis-
tributed there and being officially controlled) for the Far
East, Indian subcontinent, Australia and New Zealand
DISEASE CONTROL
Synthetic fungicides have been the main method of citrus
post-harvest disease control (Eckert 1990). There is how-
ever, a growing international concern over the often indis-
criminate use of synthetic fungicides on food crops because
of the possible harmful effects on human health and the
