This disease occurs mainly when the weather is humid with moderate temperatures.
Damage Symptoms:
Initially, round to irregular papules with dark brown to black centres and yellow halos appear on the leaves.
Later, the spots become larger and fuse to form a large necrotic area, resulting in a significant portion of the leaf being damaged. The leaf may drop off prematurely.
The infected plants are stunted, and the decline in the size of the foliage affects photosynthesis, leading to poor growth.
The spots may also occur on the stems and heads, reducing the quality of the curd (head).
Preventive Measures:
Practice crop rotation.
Ensure proper spacing is maintained between the plants so that there is good air circulation.
Control Measures:
Apply Mancozeb at 2.5 g/l or Chlorothalonil at 1 g/l at 15 and 30 days after sowing.
