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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
166 Postharvest Diseases of Fruits and Vegetables
sporulation of these fungi on diseased fruits and protect them from
infections through new wounds sustained after treatment (Brown, G.E.,
1983). The fungicide is markedly effective against sour rot (Geotrichum
candidum) but provides only moderate protection against the stem-end
fungi, Alternaria citri, Phomopsis citri and Diplodia natalensis. The
ability of etaconazole to control the major pathogens of harvested citrus
fruits gives this fungicide a very important role as a postharvest
fungicide for these fruits. Trials with Fuerta avocados have shown that
etaconazole controls stem-end rot but is not effective against anthracnose
(Muirhead et al., 1982). However, both anthracnose and stem-end rot in
mangoes have been controlled by this compound during storage and
ripening of the fruit (Spalding, 1982).
Guazatine is a fungicide with a wide spectrum of activity, capable of
eradicating incipient infections by the two Penicillia, including
benzimidazole-resistant isolates, as well as infections by Geotrichum in
citrus fruit (Brown, G.E., 1983). The fungicide is also efficient in
controlling Geotrichum and Alternaria in melons (Wade and Morris,
1983).
Metalaxyl (ridomil), which is an acylalanine fungicide, acts as a
strong inhibitor of the various developmental stages oi Phytophthora spp.
(Bruck et al., 1980; Farih et al., 1981). In addition to the inhibition of the
mycelial growth of the fungus, the fungicide generally inhibits the
formation of sporangia, chlamidospores and oospores at low
concentrations. This systemic fungicide uniquely arrests incipient
infections of Phytophthora in citrus fruits and prevents contact spread of
brown rot during prolonged storage (Cohen, 1981, 1982). Application of
metalaxyl, in a water-wax formulation, to Phytophthora citrophthorainoculated
Shamouti oranges, followed by the standard packinghouse
procedure (including washing, immersion in a 0.5% sodium ortho
phenylphenate for 3 min at 36°C, washing in tap water and drying), has
shown that the fungicide considerably delays or prevents the
development of brown rot in storage. The antifungal effect on
Phytophthora is much more pronounced than that of TBZ or imazalil, but
it has no influence on the development of other postharvest pathogens.
However, the combination of metalaxyl with etaconazole, in a water-wax
formulation, broadens the scope of the antifungal activity and controls
Penicillium rots, sour rot {Geotrichum) and brown rot {Phytophthora) in
citrus fruits (Cohen, 1981).
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