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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
34 Postharvest Diseases of Fruits and Vegetables
amount of rainfall in the principle infection period (Timmer and Fucik,
1975).
Cultural practices, such as pruning of fruit trees and destruction of
crop debris, can markedly affect the survival of pathogenic
microorganisms (Palti, 1981). Application of preharvest fungicides can
directly reduce the level of infestation. However, preharvest chemical
sprays, with the same chemical that is designated for postharvest
application, can enhance the production of new fungal strains resistant
to that fungicide (Eckert and Ogawa, 1988). Cultural practices can also
be changed in order to reduce the inoculum level through sanitation, or
to produce conditions less favorable for disease by modifying the canopy
microclimate (Legard et al., 1997). Plant spacing within the row may also
affect the incidence of rot. Legard et al. (2000) found that wider
within-row plant spacing reduced Botrytis rot in strawberries compared
with narrower spacing. This may be due to the increased number of
target hosts available to intercept inoculum in the latter case, or to the
fact that more fruit may escape timely harvesting and thus contribute to
increased levels of inoculum. Increased plant density could also reduce
the efficacy of fungicide applications by reducing plant coverage (Legard
et al., 2000). Soil solarization, applied in hot countries by covering the
soil with clear plastic film to heat the soil to a lethal temperature (Katan,
J., 1987), or steam sterilization and fumigation applied in cooler
countries, are practices which help to cleanse the soil by destroying
harmful organisms. The sequence of crop rotation in the field can reduce
the source of infection and thus influence the quality of the harvested
commodity by affecting the health of the subsequent crop (Palti, 1981).
Field nutrition, too, can have an impact on the development of storage
decay. Thus, the rapid development of bacterial soft rot in tomato fruits
depends, to a great extent, on the application of nitric fertilizer to the
plant while in the field (Bartz et al., 1979), and the resistance of pears to
postharvest decay increases after the trees have been given nitrogen and
calcium (Sugar et al., 1992). Despite all these data, the linking
relationship between stimulating nutrients within the host and its
susceptibility to the pathogen is quite unclear.
Harvesting by hand is the predominant method for fruits and
vegetables destined for the fresh produce market (Kader et al., 1985).
With proper training, pickers can select for the optimal maturity stage of
a given commodity and can keep damage to a minimum. Mechanized
harvesting, even when used correctly, can cause substantial damage to
the commodity, which may serve as suitable areas of penetration for
http://arab2000.forumpro.fr