Blight Disease Control — How to Identify, Treat & Prevent Early and Late Blight
Blight is one of the most widespread fungal diseases in Indian agriculture, affecting tomato, potato, paddy, and many other crops. Correct identification and timely fungicide application are essential to limit crop losses.
How to identify blight
Watch for these signs in your field.
Dark brown lesions with yellow halo
Circular to angular brown spots with a yellow margin on older leaves (Early Blight). In Late Blight, lesions are water-soaked and turn dark brown with white sporulation.
Water-soaked spots on stems/fruits
Affected stems and fruits show greasy, water-soaked patches that rapidly enlarge and turn dark brown (Late Blight).
Blighting and defoliation
Severe infection causes rapid browning, withering, and shedding of leaves. Entire plants can die within 7–10 days under conducive conditions.
How to control blight
Follow this step-by-step protocol for best results.
Remove and destroy infected plant material
Remove infected leaves, stems, and fruits. Do not compost them — burn or bury deeply to reduce the inoculum load.
Apply protective fungicide before infection
Spray Mancozeb 75% WP (2 g/L) or Chlorothalonil 75% WP (2 g/L) preventively every 10–12 days during humid weather (above 85% RH, temperature 15–25°C).
Switch to systemic fungicide at first symptoms
At first sign of disease, switch to Azoxystrobin + Difenconazole (1 ml/L), Propiconazole 25% EC (0.1%), or Metalaxyl + Mancozeb (2 g/L) for Late Blight.
Which crops are at risk?
Tap a crop for the full pest management guide.
Blight — Common Questions
What is the difference between early blight and late blight?
Early Blight (Alternaria solani) causes concentric ring lesions on older leaves with a yellow halo. Late Blight (Phytophthora infestans) causes water-soaked lesions that spread rapidly under cool, wet conditions (15–20°C). Late Blight is much more destructive and requires Metalaxyl-based fungicides.
Which fungicide is best for late blight in tomato/potato?
For Late Blight, use Metalaxyl + Mancozeb (Ridomil Gold, 2 g/L) or Dimethomorph + Mancozeb (2 g/L). These have systemic action against Phytophthora. Combine with a contact fungicide (Chlorothalonil) to reduce resistance risk.
How to prevent blight from spreading to healthy plants?
Spray preventively before the disease appears — don't wait for symptoms. Ensure good air circulation by proper plant spacing, avoid overhead irrigation, and apply mulch to reduce soil splash. Remove and destroy infected crop debris immediately.
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