Downy Mildew of Grapes

Downy Mildew of Grapes:-

Pathogen:- 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 %.