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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
150 Postharvest Diseases of Fruits and Vegetables
Although a postharvest treatment is usually more effective in cases
where wound infection is involved, preharvest sprays may be a suitable
control means when considerable harvest injury is involved and handling
practices make postharvest treatment difficult to apply soon after
harvest. Thus, orchard sprays may be the best means for reducing decay
in peaches that will be subjected to controlled ripening after harvest, and
in oranges that will be subjected to degreening, since both of these
practices often increase decay by wound pathogens (Eckert and Ogawa,
1985).
When dealing with preharvest sprays, it is important to emphasize the
need for careful selection of the fungicides. With the emergence of fungal
strains resistant to chemicals, we frequently need to replace a chemical,
previously proven to be effective, with another chemical or with two or
several different compounds. Furthermore, there is a significant risk that
residues from preharvest treatments will encourage the buildup of
fungicide-resistant strains of the pathogens, and these will not allow us
to benefit from postharvest treatment with the same fungicide or with
related fungicides with similar chemical structures (Eckert and Ogawa,
1988).
B. SANITATION
Fruits and vegetables that have been injured during harvest or
shipping, and have succeeded in avoiding infection by wound pathogens,
are still liable to come into contact with the pathogens during packing or
storage. Since disease development requires the presence of a given
pathogen along with an available wound for penetration, a reduction in
either of these factors will lead to the suppression of disease
development.
Wounding can be minimized by careful harvesting, sorting, packaging
and transportation, including preventing the fruit from falling at all
stages. Regarding the avoidance of wounds one should remember that
physiological injuries caused by cold, heat, oxygen deficiency, and other
environmental stresses, also predispose the commodity to attack by
wound pathogens. A general reduction in wound formation should also
take such factors into consideration, even when no external symptoms
can be distinguished.
The level of inoculum may be reduced by careful and strict sanitation
procedures. The air of the packinghouse permanently carries an
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