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Horticultural crops : Grapes
Downy mildew: Plasmopara viticola

Symptoms

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

Management

  • Spray Bordeaux mixture 1 % or Metalaxyl + Mancozeb 0.4 %.
Infected leaves
Grapes downy mildew in bunches

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