Early blight (Alternaria solani) is a serious fungal disease affecting tomatoes and potatoes. Damage includes 30–50% yield loss if untreated. This guide covers identification, organic/chemical controls, and prevention strategies.
Early Blight Symptoms
- Concentric brown rings on lower leaves ("target" pattern)
- Yellowing around lesion
- Leaf drop starting from bottom of plant
- Affects stems, fruit in advanced cases
- Peak season: Warm (21–27°C), wet conditions; fungal spores spread via water
Organic & Chemical Control
Organic Options
| Method | Cost | Efficacy |
|---|---|---|
| Copper fungicide (0.5–1%) | 200–400/kg | 70–80% |
| Chlorothalonil | 400–800/L | 80–90% |
| Sulfur | 200–400/kg | 60–70% |
| Bacillus subtilis (biocontrol) | 500–1,000 | 65–75% |
Prevention
- Leaf removal: Remove all leaves below 30 cm at transplant; continuous removal of diseased leaves
- Staking: Improves airflow, reduces humidity
- Drip irrigation: Avoids wetting foliage (spores need moisture)
- Resistant varieties: 'Mountain Magic', 'Iron Lady' (genetic resistance)
- Crop rotation: 3-year minimum away from tomato/potato
- Sanitation: Burn infected leaves/debris (don't compost)
Spray Schedule
| Week | Action |
|---|---|
| Week 1–4 | Monitor; remove lower leaves |
| Week 5–8 | Spray at first sign: copper or chlorothalonil |
| Week 9–12 | Continue sprays every 7–10 days if weather wet |
| Harvest | Remove all remaining plant material |
Cost-Benefit (1-Hectare Tomato)
Untreated: 30–50% yield loss = 9–15 t lost (270–600k PKR) Treated: Copper sprays + labor = 5–10k PKR ROI: 2,700–12,000% (prevention highly profitable)
FAQ
Is early blight the same as late blight? No. Early blight (Alternaria) affects lower leaves in warm conditions. Late blight (Phytophthora) affects entire plant in cool/wet conditions and is more severe.
Can I prevent blight without fungicides? Partially. Aggressive leaf removal (cultural control) prevents 40–60% of damage. Combine with 1–2 copper sprays for 90%+ control.
Related Guides
Check early blight risk for your region on our crop calendar.
Frequently Asked Questions
Is early blight the same as late blight? +
No. Early blight (
Can I prevent blight without fungicides? +
Partially. Aggressive leaf removal (cultural control) prevents 40–60% of damage. Combine with 1–2 copper sprays for 90%+ control. ---