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

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Postharvest Disease Summary 309
spores. To control brown rot {Monilinia spp.) sanitation should include
the removal of blighted flowering shoots and mummified fruits from the
orchard (Holz et al., 1998) along with careful harvesting and handling to
avoid injuries that would enable easy penetration of the pathogen into
the fruit. Fungicidal sprays are generally necessary to protect the flowers
from infection and to control brown rot in the orchard (Zehr, 1982).
Postharvest fungicide treatments with dips, sprays or wax formulations
containing a systemic fungicide have provided good control of
M fructicola. However, with the appearance of resistant strains of the
pathogen, the use of unrelated chemicals has been recommended
(Michailides et al., 1987). Combinations of different fungicides have been
effective in controlling both brown rot and Rhizopus rot (Wade and
Gipps, 1973). The effectiveness of fungicides against brown rot may be
improved by combining them with a hot water treatment. Such a
combination has enabled the concentration of the fungicide to be reduced
without impairing the effectiveness of the treatment (Jones and Burton,
1973).
Hot water alone (52°C, 2.5 min) has been found to control incipient
infections of M fructicola and R. stolonifer in nectarines and peaches, but
the control was accompanied by physiological injuries to the fruit.
Combining hot water treatment with a fungicide enabled decay control to
be achieved at a lower temperature, and no injury was observed during
storage (Smith, W.L. and Anderson, 1975). However, Phillips and Austin
(1982) found that some changes in peaches had already developed after
treatment with hot water above 45°C. When stone fruits are immersed in
a hot water fungicide bath, the time of immersion and the temperature
should be carefully controlled to avoid fruit injury. Heat injury of the
fruit may also lead to increased sensitivity to P. expansum infection
(Smith, W.L. and Anderson, 1975).
Several calcium salts, particularly calcium propionate and calcium
silicate, were found to reduce both the incidence and the severity of
brown rot in wound-inoculated peaches (Biggs et al., 1997). The salts
directly reduced M fructicola growth and inhibited its pectolytic activity.
Minimal growth and maximal inhibition of enzymatic activity occurred
after calcium propionate application.
Several studies have been dedicated to the control of postharvest
diseases of stone fruits by biological means. Whereas the first biocontrol
studies focused on the use of antagonistic bacteria, later studies used
mainly yeast species and epiphytic fungi. The control of brown rot and
Rhizopus rot in peaches was achieved with the bacteria. Bacillus subtilis
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