Horticultural crops : Grapes
Downy mildew: Plasmopara viticola
Symptoms
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Irregular, yellowish, translucent sports on the upper surface of the leaves.
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Correspondingly on the lower surface, white, powdery growth on leaves.
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Affected leaves become, yellow, brown and gets dried.
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Premature defoliation.
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Dwarfing of tender shoots.
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Brown, sunken lesions on the stem.
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White growth of fungus on berries which subsequently becomes leathery and
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shrivels.
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Later infection of berries result in soft rot symptoms.
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No cracking of the skin of the berries.
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Spread : Through sporangia by wind, rain etc.
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Survival : As oospores present in the infected leaves, shoots and berries. Also as
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dormant mycelium in infected twigs.
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Optimum temperature : 20-22°C
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Relative humidity : 80-100 per cent
Management
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Grapes downy mildew in bunches |
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