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

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328 Postharvest Diseases of Fruits and Vegetables
from preharvest infection (Eckert and Ogawa, 1988). Preharvest sprays
with chlorothalonil are also effective in controlling A. alternata during
storage (Davis et al., 1997). Sprays with two fungicides (metalaxyl and
mancozeb) combined effectively control P. infestans in the field, reduce
the inoculum level and minimize infections that lead to decay
development in the markets (Eckert and Ogawa, 1988).
Use of chlorinated water at 38-43°C to wash tomatoes in the
packinghouse prevents the buildup of inoculum in the water. The water
should be properly chlorinated and frequently changed (Bartz, 1982) and
the fruit has to be dried before being packed. After removal of the surface
water, the fruit may be treated with postharvest fungicides. Postharvest
fungicidal dips (using imazalil) were found to be effective against
A. alternata in tomatoes and peppers (Spalding, 1980) and against
B. cinerea in tomatoes (Manji and Ogawa, 1985). Most of the chemical
compounds used are ineffective against G. candidum (Eckert and Ogawa,
1988).
Rotting is often retarded in storage since the pathogens grow very
slowly at or below 10°C. However, the correct storage temperature
should be carefully maintained, to prevent chilling injury (Kader, 1986),
which enhances susceptibility to infection (Barkai-Golan and
Kopeliovitch, 1981, 1989). While ripe tomatoes can be held for a few days
at 7-10°C, mature green fruits, which are more susceptible to low
temperature injury, should usually be held at or above 13°C. Relatively
high storage temperatures are also recommended for the chill-sensitive
eggplants (8-12°C) and peppers (7-10°C).
Reduction in the incidence of B, cinerea, R, stolonifer and A. alternata
could also be achieved by biological means (Chalutz et al., 1991):
application of a known antagonistic yeast (Pichia guilliermondii) to
wounds on the surface of harvested ripe tomato fruits, prior to
inoculation with the pathogens, reduced decay by 90%. The yeast had no
effect on the pathogens in culture and its inhibitory effect on pathogens
on the fruit was attributed to competition for nutrients. The efficacy of
the antagonist in reducing decay was affected by the concentrations of
both the yeast cells and the fungal spore suspension used for inoculation.
Fruits of the non-ripening tomato mutants, nor (non-ripening) and rin
(ripening inhibitor), which are devoid of typical carotenoids of tomato and
fail to soften (Tigchelaar et al., 1978), have been found to be less
susceptible to postharvest diseases than normal tomato fruits
(Barkai-Golan and Kopeliovitch, 1981; Lavy-Meir et al., 1989). Increased
resistance toward B, cinerea has also been exhibited by the hybrid fruit
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