India’s most valuable fibre crop and the livelihood of 6 million farmers across Maharashtra, Gujarat, Telangana, and Punjab — at the centre of the country’s agricultural economy and its deepest insecticide resistance crisis.
Cotton : 5 Major Threats and Their Control
For educational purposes only. Recommended crop varieties are location-specific. Always verify chemical and variety recommendations with your local KVK or State Agriculture Department.
1. Pink Bollworm
(Pectinophora gossypiella)
The Threat:
- The pink bollworm larva enters through the bract or floral disc and bores into the boll, feeding on seed and lint from inside, remaining hidden until the boll is opened.
- By the time external symptoms appear — staining, incomplete opening — the larva has already finished feeding and moved to another boll.
- First-generation Bt cotton with the Cry1Ac gene was highly effective against the bollworm complex until around 2009, when field resistance was confirmed.
- By 2015, resistance had spread across the cotton belt, and the yield protection from Bt alone is now seriously reduced in many areas.
The Solution:
- Use Bt cotton hybrids with stacked toxin genes (Cry1Ac + Cry2Ab) (commonly known as Bollgard II).
- Strictly maintain 20% non-Bt refuge rows as per GEAC (Genetic Engineering Appraisal Committee) rules — this is not optional.
- Install pheromone traps (Semiochemical — for adult male monitoring) @ 5 per hectare and take spray decisions based on trap catches.
- Apply Emamectin Benzoate 5 SG (Biological-derived Insecticide — Avermectin) @ 0.4 g/litre only in real outbreak situations, based on trap data.
2. Whitefly (Bemisia tabaci) and Cotton Leaf Curl Virus (CLCuV)
The Threat:
- The cotton whitefly is both a direct pest and a virus vector of devastating consequence.
- As a direct pest, dense nymph populations on the underside of leaves suck phloem sap and release honeydew, leading to sooty mould that reduces photosynthesis.
- As a vector, a single adult whitefly can acquire Cotton Leaf Curl Virus (CLCuV) — a complex of geminiviruses — from an infected plant and spread it to many healthy plants through continuous feeding.
- CLCuV causes leaf curling, vein thickening, and complete boll set failure.
The Solution:
- Spray mineral oil (Physical Insecticide / Anti-feeding Agent) — light spray oil @ 2% — to reduce whitefly feeding and virus spread; this is the most specific measure to prevent CLCuV transmission.
- Use yellow sticky traps (Physical Monitoring Tool) @ 15–20 per hectare for monitoring whitefly population.
- Apply Spiromesifen 22.9 SC (Insecticide — Tetronic Acid Derivative) or Triazophos + Cypermethrin (Contact Insecticide combination) only at genuine threshold.
- Grow recommended CLCuV-tolerant varieties.
3. American Bollworm / Cotton Bollworm
(Helicoverpa armigera)
The Threat:
- Helicoverpa armigera is a globally multi-resistant insect pest — with documented resistance to organophosphates, carbamates, pyrethroids, indoxacarb, and even newer insecticides in different populations worldwide.
- In cotton, the larva bores into bolls and feeds on developing seeds and lint, causing 10–30% yield loss if not managed.
- Its insecticide resistance history in India clearly shows the risks of calendar-based spraying and repeated use of a single mode-of-action insecticide.
The Solution:
- Apply HaNPV (Biological Insecticide — Baculovirus) @ 250 LE/ha when young larvae first appear — it is the base of bollworm control.
- For the first chemical spray, use Spinosad (Insecticide — Spinosyn) 45 SC @ 0.3 ml/litre.
For the second spray, switch to Indoxacarb 14.5 SC (Systemic Insecticide — Oxadiazine) @ 0.5 ml/litre. - Do not use the same insecticide group repeatedly — always rotate different types to prevent resistance.
4. Tobacco Caterpillar / Semi-looper
(Spodoptera litura)
The Threat:
- Spodoptera litura migrates in mass larval movements from surrounding weed hosts into cotton fields in August–September, defoliating entire blocks of plants within 48–72 hours.
- Population outbreaks are often triggered and increased by earlier broad-spectrum insecticide sprays that kill natural enemies — spiders, predatory bugs, and parasitoids.
- Fields with a history of heavy pyrethroid use are most severely affected; the link between insecticide overuse and S. litura outbreaks is direct and widely recognised.
The Solution:
- Apply SlNPV (Spodoptera Nuclear Polyhedrosis Virus) (Biological insecticide — baculovirus) @ 250 LE/ha when larvae are first seen.
- Install pheromone traps (Semiochemical) @ 5–6 per hectare to monitor adult moths and predict outbreaks.
- Spray Chlorantraniliprole 18.5 SC (Systemic insecticide — Diamide) or Indoxacarb 14.5 SC only when the pest reaches economic threshold levels.
- Do not use pyrethroids at all — they are the main cause of Spodoptera litura resurgence.
5. Root Rot / Wilt Complex
(Fusarium, Rhizoctonia, Macrophomina)
The Threat:
- A complex of soil-borne fungi attacks the roots and collar of cotton plants, causing sudden wilting in circular patches that spread during the growing season.
- Most common in fields with a long history of continuous cotton cultivation without rotation.
- Worse in fields with waterlogging after heavy kharif rainfall.
- The wilt complex involves multiple pathogens acting together, so no single fungicide can control all the causes.
The Solution:
- Treat seeds with Trichoderma viride (Biological Fungicide — Beneficial Soil Fungus) @ 4 g/kg, along with Metalaxyl + Thiram (Systemic + Contact Fungicide combination) as a combined seed treatment.
- Do soil solarisation using clear polyethylene mulch in May–June to kill disease-causing organisms with heat.
- Follow at least a 3-year crop rotation, including one kharif cereal (sorghum or maize), to break the soil-borne disease cycle.
Additional Reads
Ph.D. in Agricultural Engineering.