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Causal Agent:
Cladosporium cucumerinum
Distribution:
North America, Africa, Europe and Asia
Symptoms:
The disease is most serious on cucumber, but can also affect cantaloupe,
pumpkin and squash. Symptoms resemble angular leaf spot in that circular
to angular, brownish, watersoaked spots with yellow margins appear on
the leaves. Young tissue, when attacked, becomes watersoaked and quickly
dies. Infected plants may have shortened internodes which give the
appearance of cucumber mosaic virus infection. A gray to olive mold can
develop on infected tissue. Cotyledons, stems, leaves and fruit can all
be attacked. Watersoaked spots appear on young fruit which develop into
crater-like depressions as the fruit grows. Later, the infected area
becomes an irregular, corky, tan scab. Often a gummy brown substance
appears on the scabby surface. An olive colored mat of fungal spores can
also develop on the fruit during humid weather. On melon the stem scar,
as well as other areas, are infected. The fruit decay is usually shallow
and spongy.
Conditions for Disease Development:
The organism survives on infected plant material. The spores are moved by
wind, clothing, insects and farming equipment. The disease develops
rapidly under cool, moist conditions. High temperatures reduce the
disease.
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