Downy Mildew: Perenospora schachtti

Symptoms

• The disease is mostly prevalent during the cooler months.
• Symptoms appear as irregular greasy greyish areas on the leaves. Under moist conditions, these areas expand rapidly and a white powdery growth appears on the lower surface of the affected leaves.
• Affected leaf dries and shrivels quickly. Flower shoots on infected plants become stunted and distorted.
• The entire inflorescence has a compact appearance and excessive leaf development may give an appearance witches broom.
• The fungus survives on the crop residues in the soil and is also carried by the seed.

Management

• Preventive measures such as good field sanitation, crop rotation and use of resistant cultivars is recommended.
• Seed treatment with Thiram (2.5-3 g/kg of seed) protects the emerging seedlings from the disease attack.
• Spraying with Dithane Z-78 (0.3 %) thrice at an interval of 15 days is also recommended as an effective control measure.