Description:

• This fungus survives in crop debris as dormant mycelium.
• High humidity, intermittent rains, and moderate temperatures are favourable conditions for the occurrence of this disease.

Damage Symptoms:

• Although the disease can affect plants at any stage, it is most severe when plants are 45-60 days old.
• Small, round, brown spots with a purple margin appear on the leaves.
• On older leaves, the necrotic centres of these spots may show a pattern of concentric zonation.
• Multiple spots may merge to form larger blighted areas.
• In humid weather, the spots turn sooty black, leading to premature defoliation.
• In severe cases, the leaf stalks and balls also become infected, showing spherical or elliptical purple spots.

Preventive Measures:

• Remove and destroy any infected plant debris.
• Perform deep ploughing in the summer.

Control Measures:

• Spray Mancozeb at 0.25% or Copper Oxychloride at 0.3%.