Post harvest diseases fruits and vegetables - Xavier University ...

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
302 Postharvest Diseases of Fruits and Vegetables
these fungicides contributed to their persistence in the fruit throughout
the storage period exerting continuous pressure for the selection of
resistant strains of Penicillium expansum and Botrytis cinerea, which
would not be controlled by postharvest treatments (Eckert and Ogawa,
1988).
Various fungicides with differing modes of action are applied after
harvest, alone or in combination, to control postharvest infections
initiated by wound pathogens, such as P. expansum, B. cinerea,
Alternaria alternata, Cladosporium herbarum and Aspergillus spp. (see
the chapter on Chemical Means). Protection against Phytophthora spp.,
which can invade apple fruits before harvest, should be provided by
orchard sprays. A postharvest treatment has to contend with infections
aged several days, and should also be able to prevent the contact spread
of the pathogen during storage (Edney, 1978; Edney and Chambers,
1981). Mucor piriformis, which can also spread during storage, cannot be
controlled by most of the fungicides; the common method for controlling
this pathogen is the addition of chlorine or sodium or^/io-phenylphenate
to the washing water in the packinghouse, to reduce the level of
pathogenic fungal spores brought into the water with the fruit (Spotts
and Peters, 1982b).
Calcium treatments applied primarily to control physiological
disorders in apples have also resulted in reduced fungal infection.
Preharvest calcium sprays were found to reduce the incidence of storage
lenticel rot caused by Gloeosporium spp. (Sharpies and Johnson, 1977)
and bitter rot caused by Colletotrichum gloeosporioides and C. acutatum
(Biggs, 1999). A reduction in the rate of P. expansum rot was found after
postharvest calcium application (Conway and Sams, 1983; Conway et al.,
1987; 1994a). Although the reduction in disease development following
calcium treatments has generally been attributed to the suppression of
physiological diseases and the improved keeping quality of the fruit,
direct effects of calcium on spore germination and colony growth have
been recorded for several pathogens, such as P. expansum, B, cinerea
(Conway et al., 1994a) and Colletotrichum spp. (Biggs, 1999). (See the
chapter on Means for Maintaining Host Resistance - Calcium
Application).
Several studies have reported on the ability of antagonistic
microorganisms to control postharvest diseases of apples. Control of both
B. cinerea and P. expansum, the two major pathogens of apple fruit, was
achieved with several epiphytic bacteria isolated from apple leaves
(Sobiczewski et al., 1996). The yeast, Candida oleophila was effective in
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