Late Blight in Tomato
टमाटर में लेट ब्लाइट — पहचान और नियंत्रण
Introduction / परिचय
Late blight (Phytophthora infestans) is the most destructive disease of tomato and potato worldwide. Under cool, humid conditions it can destroy an entire crop within 7–10 days. Rapid identification and timely fungicide application are critical.
लेट ब्लाइट (Phytophthora infestans) टमाटर और आलू की सबसे विनाशकारी बीमारी है। ठंडी, नम परिस्थितियों में यह 7–10 दिनों में पूरी फसल नष्ट कर सकती है।
Identification / पहचान
Leaf Symptoms / पत्ती लक्षण
- Water-soaked, pale green patches on older leaves — typically at leaf margins or tips
- Lesions enlarge rapidly to irregular dark brown/black areas
- White cottony sporulation (sporangiophores) visible on leaf undersides in humid mornings
- Entire leaf blackens and collapses in 3–5 days
- पुरानी पत्तियों पर पानी-सोखे, हल्के हरे धब्बे — आमतौर पर किनारों या नोकों पर
- धब्बे तेजी से अनियमित भूरे/काले क्षेत्रों में बदलते हैं
- नमी वाली सुबह पत्ती के नीचे सफेद रुई जैसी स्पोरुलेशन दिखती है
- पत्ती 3–5 दिनों में पूरी तरह काली पड़ जाती है
Stem and Fruit Symptoms / तना और फल लक्षण
- Dark brown lesions on stems — can girdle and collapse the stem
- Fruit: irregular, greasy, dark-brown lesion on green or ripe tomatoes; internal brown rotting
Favourable Conditions / अनुकूल परिस्थितियां
- Temperature: 10–20°C (night cool, day mild)
- Relative humidity: >90% for 6+ continuous hours
- Rain, overhead irrigation, or heavy dew
- Dense canopy that traps moisture
Rule of thumb: Two consecutive days of cool, wet weather = apply protective fungicide immediately.
Integrated Management / एकीकृत प्रबंधन
Cultural Control / सांस्कृतिक नियंत्रण
- Use resistant/tolerant hybrids (e.g., Naveen, Arka Rakshak)
- Avoid overhead irrigation — use drip
- Maintain proper plant spacing (60 × 45 cm) for airflow
- Remove and destroy infected plant material immediately
- Do NOT grow tomato adjacent to potato fields
Chemical Control / रासायनिक नियंत्रण
Protective fungicides (apply before disease onset / साप्ताहिक रोकथाम के लिए):
| Product | Active Ingredient | Dose/acre |
|---|---|---|
| Mancozeb 75% WP | Mancozeb | 400 g |
| Chlorothalonil 75% WP | Chlorothalonil | 400 g |
| Copper oxychloride 50% WP | Copper | 500 g |
Curative + Protective (when disease is active / रोग दिखने पर):
| Product | Active Ingredient | Dose/acre |
|---|---|---|
| Metalaxyl 8% + Mancozeb 64% WP | Metalaxyl-M + Mancozeb | 400 g |
| Cymoxanil 8% + Mancozeb 64% WP | Cymoxanil + Mancozeb | 400 g |
| Dimethomorph 9% + Mancozeb 60% | Dimethomorph + Mancozeb | 400 g |
| Ametoctradin 27% + Dimethomorph 20.27% SC | Initium + Dimethomorph | 400 ml |
Important: Alternate between fungicide groups to prevent metalaxyl resistance. Do not use metalaxyl-based products more than 3 times per season.
Spray Schedule / छिड़काव कार्यक्रम
- Preventive season sprays: Start from 30 DAS, repeat every 10–14 days with Mancozeb or Chlorothalonil
- High-risk conditions (cool + wet): Switch to Metalaxyl + Mancozeb, repeat every 7 days
- Active outbreak: Cymoxanil + Mancozeb; remove affected tissue; follow with 5-day spray interval
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Prevention Summary / रोकथाम सारांश
- Monitor twice a week in cool, rainy weather
- Never skip protective sprays after rain or dew
- Use drip irrigation, not sprinklers or flood
- Rotate fungicide MoA groups every spray
- Remove and burn infected plants — don"t compost
