Complete Farming Guide
Cotton Farming Guide
Gossypium hirsutum
26 million tonnes of lint — clothing half the world
Cotton is the most important natural fiber crop on Earth, providing raw material for nearly 40% of the world's textile production. Unlike food crops, cotton's value is primarily in its fiber (lint), with cottonseed oil and meal as secondary products. Cotton requires a long, frost-free growing season with abundant sunshine and careful management of vegetative-to-reproductive balance. It is one of the most input-intensive crops, requiring precise pest management, defoliation timing, and irrigation scheduling.
Quick Facts
Growing Season
Summer (Kharif)
Growth Period
150-180 days
Optimal Temp
21-35°C (70-95°F)
Water Needs
700-1300mm
Top Producer
India
Yield / Acre
700-1,200 lb lint/acre (US); 300-500 lb (developing countries)
Cotton Growth Stages — What to Do at Every Stage
Emergence & Seedling
Days 0-20What to do
Plant when soil temperature at 4-inch depth is 18°C (65°F) for 3 consecutive days. Use fungicide-treated seed. Plant 3-4 seeds per foot of row at 1 inch depth. Apply pre-emergence herbicide.
Watch for
Seedling disease complex (Rhizoctonia, Pythium) in cold, wet soils. Thrips feeding causes crinkled, silvery leaves and delayed growth — treat if 2+ thrips per plant before first true leaf.
Squaring (Pre-Bloom)
Days 21-55What to do
Scout for plant bugs (Lygus) and fleahoppers that feed on squares (flower buds), causing square shed. Apply first nitrogen split. Monitor plant height-to-node ratio — 1.5-2.0 inches per node indicates good vegetative balance. Apply mepiquat chloride (PGR) if growth is excessive.
Watch for
Square shed above 20% indicates pest pressure or stress. Small, pinhead-sized squares turn yellow-brown and fall off when pierced by plant bugs. Excessive vegetative growth ("rank cotton") from too much nitrogen or water.
Flowering (Bloom)
Days 56-100What to do
White flowers appear first, turning pink on day 2 and dropping the petal on day 3. Track NAWF (nodes above white flower) — when NAWF reaches 5, the plant is setting fruit aggressively. Continue irrigation — boll development requires consistent moisture. Apply bollworm insecticide if egg counts exceed threshold.
Watch for
Bollworm eggs on terminals and young bolls. Tarnished plant bug on squares and small bolls. Boll rot from excessive moisture and dense canopy. NAWF dropping below 3 signals early cutout.
Boll Development
Days 101-140What to do
Continue irrigation through boll fill but reduce frequency as bolls mature. Apply PGR if needed to stop vegetative growth and direct energy to boll fill. Last effective bloom date is 3-4 weeks before expected first frost.
Watch for
Boll rot (hardlock) from wet weather during open boll stage. Stinkbug damage on bolls — internal feeding causes stained lint and seed damage. Premature defoliation from stress.
Defoliation & Harvest
Days 141-180What to do
Defoliate when 60% of bolls are open. Apply defoliant (thidiazuron + ethephon) — timing is critical. Wait 14-21 days after defoliation for harvest. Apply boll opener if needed to crack remaining mature bolls.
Watch for
Defoliating too early causes immature fiber (low micronaire) and yield loss. Defoliating too late leads to weathering (fiber quality degradation from rain and wind). Green bolls at defoliation = lost yield.
Common Cotton Diseases — Identification Guide
Verticillium Wilt
Verticillium dahliae
What you will see
Interveinal yellowing and browning of lower leaves, often one-sided on the leaf. Internal discoloration of stem vascular tissue — cut the main stem and look for brown streaking in the wood. Plants wilt during hot afternoons and may recover at night initially, then permanently wilt.
Conditions that favor it
Cool soil temperatures (22-28°C), high soil moisture, and compacted soils. Builds up in continuous cotton fields. The pathogen persists in soil for 10+ years as microsclerotia.
Fusarium Wilt
Fusarium oxysporum f. sp. vasinfectum
What you will see
Similar to Verticillium wilt but more severe in warm conditions. Yellowing, wilting, and death of plants, starting in patches. Vascular browning is darker and more extensive. Often associated with root-knot nematode — the nematode wounds allow Fusarium entry.
Conditions that favor it
Warm soil temperatures (above 28°C), sandy soils, and root-knot nematode co-infection. Acidic soils (pH below 6.0) favor disease. Race 4 (FOV4) is an aggressive new race spreading in the US and Australia.
Bacterial Blight
Xanthomonas citri pv. malvacearum
What you will see
Angular, water-soaked lesions on leaves that turn brown to black, limited by leaf veins (giving them an angular shape). Black lesions on stems ("black arm"). Boll rot with sunken, dark lesions that stain lint. Spreads rapidly in rain with wind.
Conditions that favor it
Warm (28-35°C), wet weather with wind-driven rain. Seed-borne inoculum is the primary source. Overhead irrigation and mechanical harvesting spread the pathogen.
Cotton Leaf Curl Virus (CLCuV)
Begomovirus (Cotton leaf curl Multan virus complex)
What you will see
Upward curling of leaves with thickened, dark-green veins ("enation" — small leaf-like outgrowths on the underside of leaves along veins). Severely affected plants are stunted with reduced boll production. Transmitted by whitefly (Bemisia tabaci).
Conditions that favor it
Transmitted by whitefly. Devastating in South Asian cotton (Pakistan, India) where it has caused epidemics with 50-80% yield losses. Hot, dry conditions favor whitefly population buildup.
Boll Rot Complex
Multiple fungi (Diplodia, Aspergillus, Fusarium)
What you will see
Bolls fail to open properly, with dark, rotted internal tissue. Lint inside is discolored (brown, gray, or green), matted, and may have visible fungal growth. "Hard lock" — boll carpels lock together and cannot be picked cleanly. Reduces fiber quality dramatically.
Conditions that favor it
Wet weather during boll opening stage. Dense canopy with poor air circulation. Insect damage (bollworm entry holes) provides fungal entry points. Late-season irrigation extending into boll opening.
Common Cotton Pests — Identification & Damage
Cotton Bollworm (Helicoverpa armigera)
Damage
The most damaging pest of cotton worldwide. Larvae bore into squares (causing shed), flowers, and developing bolls, feeding on developing seeds and lint. A single larva can destroy 4-5 bolls. Boll damage creates entry points for boll rot fungi. Yield losses of 30-50% occur in unmanaged fields.
How to identify
Larvae are variable — green, brown, or pink with light stripes. Look for a single egg on terminals and young fruiting structures (the egg is white, dome-shaped, 0.5mm). Check for entry holes in bolls with frass at the opening. Adult moths are tan-brown with a distinctive kidney-shaped mark on the forewing.
Pink Bollworm
Damage
Larvae bore into developing bolls and feed on seeds, causing "rosetted" blooms (petals fused together and don't open properly). Damaged seeds have reduced oil content. Lint quality is degraded by larval feeding channels. Historically the most devastating cotton pest in South Asia, Middle East, and the US Southwest before sterile insect releases.
How to identify
Small (12mm) pink-striped larvae inside bolls. Adults are small (10mm wingspan) gray-brown moths. Rosetted flowers are the most visible field sign — flowers that fail to open normally and appear pinched at the base. Check by slicing open green bolls — larvae are found feeding between seed and boll wall.
Whitefly (Bemisia tabaci)
Damage
Sucks sap from leaves, causing yellowing and leaf drop. Excretes honeydew that coats open bolls and lint, causing "sticky cotton" — a major quality defect that jams textile machinery. Also the vector for cotton leaf curl virus (CLCuV), which is devastating in South Asia.
How to identify
Tiny (1mm) white-winged insects on leaf undersides. Shake the plant — a cloud of white flies rises. Check for sticky honeydew residue on leaves and bolls. Yellow sticky traps at canopy height for population monitoring. Threshold: 5+ adults per leaf or visible honeydew on lint.
Tarnished Plant Bug (Lygus lineolaris)
Damage
Feeds on squares, small bolls, and flowers by piercing and injecting saliva that dissolves plant tissue. Causes "dirty squares" — stained, damaged pollen. Heavy feeding causes 25-50% square shed, dramatically reducing boll set and yield. The dominant pest of cotton in the US Mid-South.
How to identify
Small (6mm), flat, brownish-green bugs with a distinctive yellow triangle on the back. Very mobile — they fly readily when disturbed. Use a drop cloth (beat sheet) to sample. Threshold: 3 per 5 row-feet of plants during squaring; 1 per row-foot during bloom.
Thrips
Damage
Feed on young leaves by rasping the surface and sucking exuded sap. Causes silvery, crinkled appearance on seedling leaves and delays plant growth by 1-2 weeks. Seedling cotton is most vulnerable — heavy thrips pressure can stunt plants permanently and delay fruiting.
How to identify
Tiny (1-2mm), slender, straw-colored insects found in terminal buds and on undersides of young leaves. Best seen by breathing on the terminal — your warm breath makes thrips move. Also detectable by tapping terminals over white paper. Threshold: 2-3 thrips per plant at the 1-2 true leaf stage.
Cotton Nutrient Management — NPK Guide
Nitrogen (N)
80-120 lb N/acre — over-application causes excessive vegetative growth
Phosphorus (P)
30-45 lb P2O5/acre based on soil test
Potassium (K)
50-80 lb K2O/acre — cotton is a heavy K user for fiber quality
Application Timing
Apply 20-30 lb N/acre at planting, with the bulk (50-70 lb) side-dressed at early squaring. Excessive early nitrogen promotes rank growth and delays fruiting. Potassium is critical for fiber quality (micronaire and strength) — apply at planting. Foliar K spray at bloom if deficiency appears.
Cotton Irrigation Schedule
Total Water Requirement
24-32 inches (600-800mm) total water use
Critical Stages
Peak bloom through boll development is the most water-sensitive period (0.25-0.35 inches/day). Deficit irrigation during vegetative stage can actually improve fruiting by limiting rank growth. Stop irrigation at 60% open boll to promote natural defoliation and fiber maturity.
Irrigation Frequency
Every 5-7 days during peak bloom in furrow-irrigated systems. Drip irrigation at 60-70% soil moisture depletion. Terminate irrigation 3-4 weeks before planned defoliation.
Cotton Economics — Cost, Yield & Profit
Cost per Acre
$750-866/acre (US irrigated)
Yield per Acre
800-1,200 lb lint/acre (US); 300-500 lb (developing countries)
Revenue per Acre
$700-1,100/acre at $0.70-0.90/lb lint
Profit per Acre
$0-250/acre (highly variable with fiber quality premiums)
Regional Context
Cotton profitability depends on both yield and fiber quality. Premium lint grades (high strength, good length, low micronaire) earn $0.05-0.15/lb above base price. In the US, cotton often competes with corn and soybeans for acreage — relative prices determine planting decisions. In South Asia and West Africa, cotton is a primary cash crop for smallholders with costs of $150-300/acre and yields of 300-500 lb lint/acre.
Frequently Asked Questions — Cotton Farming
When should I defoliate cotton?
Defoliate cotton when 60-65% of bolls are open. The standard method is to count open bolls and total bolls at several points across the field. Also check the top crop — slice open the highest green boll on the plant. If the boll wall is firm and the seed coat is dark brown with well-developed fiber, it will open after defoliation. If the seed coat is still white or green, defoliating now will result in immature fiber (low micronaire) and yield loss. Apply thidiazuron + ethephon combination for consistent results. Defoliation in cool weather (below 15°C/60°F) is poor — defoliants need warm temperatures to work. Plan for 14-21 days between defoliation and harvest for clean picking.
How do I manage cotton bollworm?
Bollworm management requires an integrated approach: (1) Scout at least 2x per week during squaring and bloom — check terminals and small bolls for eggs and small larvae, (2) Economic threshold is 8-10% damaged squares or 5% damaged bolls, (3) Bt cotton varieties (where available) provide 70-90% control of young larvae, (4) For conventional cotton, time insecticide applications to target eggs and small larvae (before they bore into bolls where they are protected), (5) Rotate insecticide modes of action to prevent resistance — diamides, spinosyns, and older chemistries in rotation, (6) Maintain beneficial insect populations through selective insecticide use — natural enemies kill 50-70% of bollworm eggs in healthy fields.
What causes sticky cotton and how do I prevent it?
Sticky cotton is caused by honeydew — the sugary excrement of whiteflies and aphids that coats open bolls and lint. In the textile mill, sticky cotton jams card machines and causes uneven yarn. Prevention starts with managing whitefly and aphid populations before bolls open: (1) Apply insecticide when whitefly counts exceed 5 adults per leaf, (2) Use selective products (spiromesifen, pyriproxyfen) that preserve natural enemies, (3) Avoid excessive late-season nitrogen that promotes whitefly-friendly lush growth, (4) Time defoliation to minimize the window when open bolls are exposed to honeydew-producing insects, (5) If honeydew is present on lint, harvest quickly — morning dew can wash some honeydew off, so harvest in the afternoon when possible.
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