Brown Spot Disease of Rice

Disease Overview :

Causal Organism: Bipolaris oryzae (fungus)
Affecting Stage: Seedling to milky grain stage (affects leaves, leaf sheath, grains)
Symptoms: Dark brown/purplish spots, yellowing, premature drying

Symptoms :

Leaf Symptoms –

• Small, round to oval dark brown or purplish spots with grey or tan centers on the leaves.
• As the disease progresses, spots become larger, typically 1-5 mm diameter, and may coalesce to form large patches.
• Severe infection leads to yellowing of leaves premature drying.

Grain Symptoms:

• Brown/black spots on the husk of developing grains.
• Poor grain filling, resulting in chaffy or discolored grains.

Seedling Symptoms:

• Narrow brown lesions
• Stunted growth, seedling blight

Favorable Conditions :

1. High humidity & temperatures between 25-30°C.
2. Nutrient-deficient soils (specially potassium and nitrogen)
3. Drought stress, improper water management
4. Dense planting, poor drainage

Control Measures :

Cultural Control –

• Disease-resistant varieties (IR-36, IR-64)
• Balanced fertilization (N, K, P)
• Good water management
• Seed treatment with fungicides
• Crop rotation, remove infected debris

Organic Control –

• Trichoderma harzianum (biocontrol agent)
• Neem cake, compost application
• Neem oil, plant-based extracts (preventive)

Chemical Control –

• Mancozeb 75% WP (Dithane M-45)
• Carbendazim 50% WP (Bavistin)
• Tricyclazole 75% WP (Beam)
• Propiconazole 25% EC (Tilt)

Effective Management

By implementing these strategies, farmers can effectively ensure good grain quality, enhance crop resilience, reduce disease severity and prevent yield losses.