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

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Chemical Control 159
increased as the duration of fumigation increased from 5 to 30 min; and
total SO2 residues were proportional to exposure time and treatment
rate, and declined sharply after fumigation. No SO2 injury was observed
on the fruit at the concentration-time combinations tested.
The possibility of using SO2 solutions against the green mold in citrus
fruits has been examined in Penicillium digitatum-inoculaited lemons
(Smilanick et al., 1995). Immersion of inoculated fruits in 2% SO2
solutions reduced green mold incidence without injuring the fruit, but
heating of the solution was needed to attain acceptable efficacy (see
Combined Applications in the chapter on Physical Means - Heat
Treatments).
The benzimidazole compounds - thiabendazole (TBZ), benomyl,
carbendazim (methyl-2-benzimidazole carbamate - MBC) and
thiophanate-methyl ~ were introduced as postharvest fungicides in the
late 1960s. The two systemic fungicides, TBZ and benomyl, have
undoubtedly added a new dimension to the control of postharvest
diseases. These compounds, whose action is associated with the
inhibition of mitosis (Davidse, 1988), are active against a broad spectrum
of pathogenic fungi. They have been used all over the world to control:
decay of citrus fruits caused by the two wound molds, Penicillium
digitatum and P. italicum and by the stem-end fungi, Diplodia natalensis
and Phomopsis citri; the brown rot caused by Monilinia fructicola in
stone fruits; blue mold (Penicillium expansum), gray mold (Botrytis
cinerea) and lenticel rot (Gloeosporium spp.) in apples; anthracnose
(Colletotrichum gloeosporioides) in banana, papaya, mango and other
tropical fruits (Eckert, 1977, 1990); and black rot (Ceratocystis paradoxa)
in pineapple (Eckert and Ogawa, 1985).
The strong inhibitory effects of the thiabendazole compounds,
especially benomyl, have been attributed to their systemic property and
their ability to penetrate the wax and the cuticle of the host surface to
reach and inhibit the pathogen beneath them (Ben-Arie, 1975; Phillips,
1975). This property enables the fungicides to act also against quiescent
infections, such as anthracnose in tropical fruits, or stem-end rot at the
button of citrus fruits. Both TBZ and benomyl act as antisporulants of
Penicillium on decaying citrus fruit and, therefore, inhibit infection of
adjacent fruits during storage and shipment. Benomyl at equivalent
concentrations is usually more effective in controlling fruit decay than
the other benzimidazole fungicides. This is in accordance with its ability
to penetrate into the cuticle of the fruit and the stem button. In providing
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