Agriculture Reference
In-Depth Information
larvae of
A
.
ludens
and
A
.
obliqua
. 'Manila' mangoes exposed
to ICA (0 kPa O
2
+ 50 kPa CO
2
) could tolerate up to 43°C
for 160 min without showing any external or internal injury
(Ortega-Zaleta & Yahia 2000). Recently, the effectiveness
of low pressure storage treatment in killing the various
tephritid fruit fly species has also been reported (Davenport
et al
. 2006). Caribbean fruit fly eggs and larvae, if exposed
to simulated hypobaric conditions for shipment of mangoes
(15 and 20 mm Hg, at 13°C, ≥98% RH), were killed by 11
days with a predicted kill of 99.999% of the eggs by 9.4
days in 15 mm Hg and 10.6 days in 20 mm Hg LP (based on
Probit 9 statistical analysis). Thus, shipment of fresh
mangoes using this technology seems promising as a means
to provide quarantine control while preserving the freshness
of fruit. However, further
in vivo
investigations are needed
to prove the technology's ability to achieve insect disinfes-
tation in mango. The approval of ICA as quarantine
treatment and its commercial adoption are still awaited.
synthetic fungicides, biological antagonists and physical
treatments are integrated to manage post-harvest diseases.
The greatest challenge is to substitute the use of synthetic
fungicides with the safer alternatives to provide the
consumer with chemical residue-free fresh fruit with high-
est quality. There is no consensus among the importing
countries about the post-harvest use of chemicals. Certain
chemicals permitted by EU countries may be banned in
North America or vice versa. The rising awareness among
consumers about the deleterious effects of synthetic
fungicides prompts the consumption of organic food and
the research on non-chemical solutions for post-harvest
diseases. Integrated anthracnose management practices in
mango at pre- and post-harvest stages have been excellently
reviewed by Arauz (2000).
Cultural control
In most of the post-harvest diseases, developing fruit are
infected in the field, but infection remains quiescent until
the onset of ripening (Figure 6.1). The development of
anthracnose is dependent upon wetness or high relative
humidity and the entire disease cycle is shown in Figure
6.1. Therefore, regulation of flowering in such a way that
the flowering, fruit set and maturation is completed in the
dry season is an ideal cultural practice to control post-
harvest anthracnose (Arauz 2000). There are some viable
options for regulation of flowering in mango. Sanitation in
the orchard can also reduce the incidence of anthracnose and
stem-end rot (Saaiman 1997a). The removal of mummified
fruit, affected twigs, and dried panicles can reduce the
inoculum load on the tree. The bagging of developing mango
fruit in the paper bags resulted in reduced anthracnose
severity, but it also reduced the red colour development,
which may affect the consumer acceptability (Hofman
et al
.
1997). The longstanding need for breeding disease resistant
cultivars in mango is still unfulfilled.
POST-HARVEST DISEASES
Mango fruit is highly susceptible to many post-harvest
diseases. The susceptibility to post-harvest diseases increases
during storage after harvest due to physiological changes
and senescence favouring pathogen development (Prusky
et al
. 2002). Anthracnose, stem-end rot and
Alternaria
rot
are the major post-harvest diseases which limit the long term
storage of the fruit. Mango is a host of several other fungal
and bacterial pathogens but these are either restricted to only
a few regions or not of much economic importance. The
wide scale prevalence of anthracnose and stem-end rot in
humid tropical areas causes heavy losses in mango fruit
(Arauz 2000; McGuire & Campbell 1993; Pelser & Lesar
1990; Rappel
et al
. 1991, 1986). Alternaria rot or black spot
is the major post-harvest disease of dry regions, for example,
Israel (Prusky
et al
. 1983, 1999, 2002). The type and strength
of post-harvest treatments for the control of post-harvest
diseases in mango should depend on the relative quiescent
infection levels (Prusky
et al
. 2002), but most of the post-
harvest disease control treatments are applied independent
of these levels. If the use of mild chemicals can give effective
disease control, there is no need to give uniform fungicide
treatment to the fruits harvested from different locations
with variable quiescent infections. The determination of
quiescent infection level in the fruit with a diagnostic kit
may prove useful for post-harvest handlers to decide which
type of treatment, mild or severe, should be given to fruit.
Post-harvest chemical control
The selection of a fungicide for post-harvest disease
control depends upon the type of fungicide used in the field
sprays and also the destination market for the fruit. A
chemical registered for use in one country may not be
permitted in another country. Benomyl and prochloraz give
good after-infection control of mango anthracnose, but
prochloraz is the only fungicide registered for post-harvest
use (Arauz 2000). Benzimidazole fungicides such as benomyl
and thiobendazole are effective for control of stem-end rot
and anthracnose as well. Benomyl was used in the past as a
post-harvest dip at rates varying from 500 to 1000 ppm, but its
use is no longer permitted. Thiobendazole (1000 to 2000 ppm)
Integrated post-harvest disease management
In a complex post-harvest handling system of mango,
cultural practices during growth, optimal use of safer
