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

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Postharvest Disease Summary 327
With progress of the disease, the lesions become dark, characterized by
salmon-pink masses of conidia in the center. In some cases black
sclerotia are also formed.
Cladosporium herbarum (Pars.) Link
Fungal conidia are generally found in the soil and are very common in
the atmosphere. However, Cladosporium rot of tomatoes and peppers is
of importance only during long transit or extended storage. The fungus is
a weak pathogen, infecting fruits via mechanical damage, or following
sunscald or chilling injury (Barkai-Golan, 1981). Lesions are circular,
firm and with definite borders; at an advanced stage and under humid
conditions, they become covered with a velvety olive-green mycelium
bearing new conidia.
Stemphylium botryosum Wallr. [perfect state: Pleospora
herbarum (Pers.) Rabenh.]
This fungus may exhibit both the asexual state (conidiophores bearing
conidia) and the sexual state (perithecia with ascospores). Infection
occurs under moist conditions, being initiated at growth cracks, the edge
of the stem scar or at any injury on the fruit surface. Lesions are similar
to those formed by A alternata, but Stemphylium is much less common.
When the fungus exhibits the sexual state, the development of
perithecia, which appear as minute black fruit bodies, may serve to
distinguish between the two fungi (McCoUoch et al., 1982).
Control Measures
To reduce infection by wound pathogens such as species of Alternaria,
Goetrichum, Fusarium, Cladosporium, Stemphylium, as well as B, cinerea
that may also gain entry through wounds, care should be taken to
prevent injury to the fruit during harvesting. Fruits showing growth
cracks, sunscald or chilling injury in the field, which predispose the fruit
to pathogen penetration, should be rejected at the packing stage.
To reduce the source of inoculum in the field, plant debris on which
the fungi can proliferate, should be removed. Good sanitation practices
around the packinghouses and regular disinfection of picking containers,
are also advisable. Since infection by soft rot bacteria depends on wet
conditions (Volcani and Barkai-Golan, 1961), the fruit should be picked
while dry.
Fungicidal treatments to control Botrytis rot on staked tomatoes start
with sprays during flowering, to protect the flowers and the young fruits
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