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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Chemical Control 163
fungicide had previously been applied successfully for several years
(Solel et al., 1996). A combination of iprodione and TBZ was found to be
advantageous in controlling the gray mold decay of celery caused by a
heterogenic spore population of B, cinerea, which comprised spores
sensitive to TBZ and/or to iprodione, along with spores resistant to these
fungicides (Barkai-Golan et al., 1993a).
Imazalil is a systemic fungicide, which was introduced as a
postharvest treatment in the early 1970s. It belongs to a group of
fungicides that act by inhibiting the biosynthesis of ergosterol, an
essential component in the membrane of fungal cells, and it was the first
ergosterol biosynthesis inhibitor to be used as a postharvest fungicide.
The fungicide is very efficient in controlling Penicillium digitatum and
P. italicum in citrus fruits, including isolates that are resistant to TBZ,
benomyl, SOPP and sec-butylamine (Harding, 1976; Eckert and Ogawa,
1985). Thanks to these properties, imazalil has become the most popular
postharvest fungicide for controlling decay in citrus fruits. As a result of
the enhanced resistance of P, digitatum and P. italicum to TBZ, imazalil
was registered in the United States in 1984 as a postharvest treatment of
citrus fruits and has been commercially used in several citrus-producing
areas of the world. Water solutions of imazalil act on the two Penicillia,
as both protectants and anti-sporulants (Laville et al., 1977). When
applied in a water-wax formulation, its effectiveness is reduced and the
concentration of the fungicide must be doubled to achieve an effect
similar to that in water solutions (Brown, G.E., 1984). It is generally
applied one or more times at relatively high dosages (2 to 4 g l-i) in a wax
formulation that covers the surface of the fruit. Following its application,
substantial antifungal residues of imazalil persist for the postharvest life
of the fruit. These conditions produce intense pressure for selection of
imazalil-resistant biotypes in the P. digitatum population and several
years after imazalil was accepted commercially for citrus decay control,
biotypes of P. digitatum with reduced sensitivity to the fungicide were
reported and their potential impact on decay control has been
demonstrated (Eckert et al., 1994).
Wild (1994) reported on differential sensitivity of P. digitatum isolates
to imazalil: while isolates obtained from Australian citrus fruits were
defined as sensitive to the fungicide, those imported from the USA were
much more tolerant, and an imazalil concentration of 0.1 mg ml^ in the
growth media was established as suitable for differentiating
imazalil-tolerant strains.
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