Cotton Bollworm Control
बॉलवर्म नियंत्रण — Identification, Monitoring & Spray Guide
Cotton Bollworm Control | बॉलवर्म नियंत्रण
Cotton bollworm (Helicoverpa armigera) is the most damaging pest of cotton in India, capable of causing 30–70% boll loss in unprotected crops. Even Bt cotton is not fully immune — late infestations can breach Bt protection. This guide covers identification, monitoring, and effective control.
Identification / पहचान
Eggs / अण्डे
Tiny, white, spherical eggs laid singly on buds, young leaves and flowers. Very difficult to see with naked eye — use magnifying glass.
Larvae / इल्ली
- Young larvae (L1–L2): small, pale green to yellowish, feed on leaf surface
- Mature larvae (L3–L6): 30–40 mm long, variable color (green, brown, black); distinctive stripes along body; bore into squares, flowers and bolls
- Entry hole into boll: circular, surrounded by frass (excrement)
- Damaged bolls: holes with yellowish frass, rotting internal cotton fiber
Adult Moth / कीट
Straw-yellow to brown moth, 15–20 mm wingspan. Active at night. Attracted to pheromone traps.
Crop Calendar / फसल चक्र में नुकसान
| Stage | Damage | Action |
|---|---|---|
| Squaring (50–70 DAS) | Square shedding — larvae eat inside square | Monitor pheromone traps; spray at threshold |
| Flowering (70–90 DAS) | Petals and stamens eaten; early boll damage | Spray Chlorantraniliprole or Emamectin |
| Boll formation (90–120 DAS) | Boll boring — direct yield loss | Economic threshold: 5+ larvae/100 plants |
| Late boll (120+ DAS) | Late season damage if wet; Bt breakdown risk | Indoxacarb or Spinosad for resistance management |
Monitoring / निगरानी
Pheromone Traps / फेरोमोन जाल
Install Helilure pheromone traps at 4–5 traps/acre from 45 DAS onward. Replace lure every 3–4 weeks.
- Action threshold: 5–7 moths/trap/week = spray required
- Traps give 3–5 days advance warning before egg hatch and larval damage
- Mass trapping (higher trap density) also provides direct reduction of adults
Insecticide Recommendations / कीटनाशक
| Insecticide | Dose / Acre | Best Use |
|---|---|---|
| Emamectin Benzoate 5% SG | 80 g/acre | Young larvae (L1–L3) — fastest knockdown |
| Chlorantraniliprole 18.5% SC | 60 ml/acre | All stages — excellent residual, stomach+systemic action |
| Indoxacarb 15.8% SC | 200 ml/acre | Resistance management rotation; effective on Bt-resistant larvae |
| Spinosad 45% SC | 75 ml/acre | Late season; resistance management |
| Profenofos 50% EC + Cypermethrin 5% EC | 400 ml/acre | Economic option for L3+ larvae in unsprayed crops |
Resistance Management / प्रतिरोध प्रबंधन
Rotate between insecticide groups every 2 sprays. Never spray the same group more than twice consecutively.
- Group rotation: Diamide (Chlorantraniliprole) → Spinosyn (Spinosad/Emamectin) → Oxadiazine (Indoxacarb) → Diamide again
- Avoid Lambda-cyhalothrin or other pyrethroids as standalone sprays — high resistance risk in bollworm
Non-Chemical Management / जैविक नियंत्रण
- HaNPV (Nuclear Polyhedrosis Virus) @ 250 larval equivalents/acre — spray in evening; kills L1–L3 larvae within 4–5 days; safe for natural enemies
- Bacillus thuringiensis (Bt) @ 500 ml/acre — effective on young larvae; must be applied before larvae enter bolls
- Trichogramma chilonis (egg parasitoid) @ 50,000/acre/week, 4–6 releases — releases timed with adult moth activity
Quick Reference | त्वरित संदर्भ
- Peak damage period: 70–120 DAS (boll formation)
- ETL: 5 moths/pheromone trap/week OR 5 larvae/100 plants
- Best insecticides: Emamectin Benzoate, Chlorantraniliprole, Indoxacarb
- Rotation is critical — resistance to older chemistries is widespread
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