Cotton:Key
KEY TO COTTON PESTS AND NUTRITIONAL DISORDERS
Contents
- 1 Seed
- 2 Seedling
- 3 Root
- 4 Stem
- 5 Leaf
- 5.1 BLACK
- 5.2 BLUE
- 5.3 BROWN
- 5.4 DARK
- 5.5 GRAY
- 5.6 GREEN
- 5.7 LIGHT
- 5.8 ORANGE
- 5.9 PINK
- 5.10 PURPLE
- 5.11 RED
- 5.12 TAN
- 5.13 WHITE
- 5.14 YELLOW
- 5.14.1 Fusarium wilt; Verticillium wilt
- 5.14.2 Compaction of soil in root zone
- 5.14.3 Lance nematode
- 5.14.4 Manganese toxicity
- 5.14.5 Misuse of substituted urea compounds or triazines
- 5.14.6 Mosaic
- 5.14.7 Nitrogen deficiency
- 5.14.8 Potassium deficiency
- 5.14.9 Reniform nematode
- 5.14.10 Sulfur deficiency
- 5.14.11 Tropical rust
- 5.15 No Distinct Discoloration
- 6 Flower
- 7 Fruit
Seed
Seed disorders are limited to disorders while in the ground and not to potential disorders inherent in the seed.
No Distinct Discoloration
Seed rot
Pregermination decay of planted seed
Seedling
BLACK
Black root rot
Black layer of decayed tissue, mostly on the surface of seedling roots, sometimes on roots of older plants
BROWN
Cold damage
Marginal to complete killing of seedling leaves; damage may be worse in lower parts of the field
Seedling disease complex
Postemergence damping-off; yellow, reddish brown, or brown decayed zones on the hypocotyl of the seedling; if the decay is girdling, seedling may topple over and die
GREEN
Wet-weather blight
Irregular dead areas in cotyledons, spreading in damp, cool weather to consume entire seedling; if spread is arrested by drying conditions, dead areas may fall out, leaving cotyledons with a ragged appearance
RED
Seedling disease complex
Postemergence damping-off; yellow, reddish brown, or brown decayed zones on the hypocotyl of the seedling; if the decay is girdling, seedling may topple over and die
YELLOW
Seedling disease complex
Postemergence damping-off; yellow, reddish brown, or brown decayed zones on the hypocotyl of the seedling; if the decay is girdling, seedling may topple over and die
No Distinct Discoloration
Crusting of soil after planting
Delayed seedling emergence; torn or distorted seedlings
Soil crusting; windblown sand; hail damage
Mutilation and distortion of seedlings
Windblown sand injury
Rapid desiccation of seedlings; water-soaked spots on young seedlings; retarded growth; death of seedlings in severe cases
Root
BLACK
Charcoal rot
A dry rot of all root tissues; plants wilt suddenly; most common in drought-stressed cotton
Fusarium wilt; Verticillium wilt
Plants dwarfed; foliage exhibits patterns of chlorotic mottling; daily wilting, with nightly recovery of plant turgor; woody part of roots, stems, petioles, and often peduncles of flowers and fruits discolored with streaks of yellow, tan, gray, or black
BROWN
Compaction of soil in root zone
Poor root development; dwarfed plants; wilting during drought stress
Phymatotrichum root rot
Half-grown plants wilt suddenly, do not recover; neighboring plants wilt and die, until a spot of dead plants forms in the field; a newly wilted plant has a decayed taproot, with the dirty, yellowish brown weft of the causal fungus on the surface
GRAY
Fusarium wilt; Verticillium wilt
Plants dwarfed; foliage exhibits patterns of chlorotic mottling; daily wilting, with nightly recovery of plant turgor; woody part of roots, stems, petioles, and often peduncles of flowers and fruits discolored with streaks of yellow, tan, gray, or black
WHITE
Sclerotium stem and root rot
Sudden wilting and death of seedlings, associated with decay of upper root system and lower stem; white mold growth surrounds hypocotyls when soil is wet
YELLOW
Phymatotrichum root rot
Half-grown plants wilt suddenly, do not recover; neighboring plants wilt and die, until a spot of dead plants forms in the field; a newly wilted plant has a decayed taproot, with the dirty, yellowish brown weft of the causal fungus on the surface
No Distinct Discoloration
Lance nematode
Foliar chlorosis and stunting, sometimes followed by defoliation
Reniform nematode
Plants severely stunted; foliage sometimes chlorotic; plants may wilt; small feeder roots destroyed; yield often reduced as much as 60%
Root-knot nematode
Plants unthrifty; often numerous beadlike swellings along the roots
Sting nematode
Severe chlorosis and stunting, followed by early death of plants; infested roots have small, sunken spots of dead tissue, become stubbed and decayed
Stem
BLACK
Bacterial blight
Dark green water-soaked cankers on stems, later becoming black in the center with red border; where the canker becomes girdling, the distal part of the stem dies
BROWN
Bacterial blight
Water-soaked spots up to 6 mm in diameter in the seedling leaves, turning dark brown upon drying, often showing slimy bacterial accumulation on surface, later drying to waxy crusts
DARK
Bacterial blight
Dark green water-soaked cankers on stems, later becoming black in the center with red border; where the canker becomes girdling, the distal part of the stem dies
GREEN
Bacterial blight
Dark green water-soaked cankers on stems, later becoming black in the center with red border; where the canker becomes girdling, the distal part of the stem dies
Manganese toxicity
Crinkled, distorted leaves; shortened internodes; and dwarfing, all tending to be severe in very acid soils
RED
Bacterial blight
Dark green water-soaked cankers on stems, later becoming black in the center with red border; where the canker becomes girdling, the distal part of the stem dies
TAN
Fusarium wilt; Verticillium wilt
Plants dwarfed; foliage exhibits patterns of chlorotic mottling; daily wilting, with nightly recovery of plant turgor; woody part of roots, stems, petioles, and often peduncles of flowers and fruits discolored with streaks of yellow, tan, gray, or black
WHITE
Sclerotium stem and root rot
Young plants wilt suddenly and die when soil is waterlogged; with continued damp conditions, the causal fungus flares out from the dying plant as a white, fanlike mold growth on the soil surface
YELLOW
Fusarium wilt; Verticillium wilt
Plants dwarfed; foliage exhibits patterns of chlorotic mottling; daily wilting, with nightly recovery of plant turgor; woody part of roots, stems, petioles, and often peduncles of flowers and fruits discolored with streaks of yellow, tan, gray, or black
No Distinct Discoloration
Acromania
Abnormally upright habit of growth; upper branches barren
Hail damage
Plant laceration and crushing
Leaf
BLACK
Charcoal rot
A dry rot of all root tissues; plants wilt suddenly; most common in drought-stressed cotton
Sulfur dioxide injury
Gray green, water-soaked zones in the foliage, later becoming brown to black
BLUE
Blue disease
Apical leaves bulge toward the base; leaf blade at first light green; entire leaf later becomes deep bluish green; symptoms occur only on parts of the plant that develop after infection is initiated
BROWN
Alternaria leaf spot
Nearly circular leaf spots up to 6 mm in diameter, with reddish brown dead centers and dark brown margins
Anthracnose
Dark brown cankers on stem, older ones showing mold growth on the surface, often with pustules full of slimy pink masses of spores
Bacterial blight
Water-soaked, angular dead areas in the leaf blade or along principal veins; diseased areas may be coated with slimy bacterial exudate; dead areas turn dark brown and dry, leaving exudate as white waxy crusts on leaf surface
Boron deficiency
Terminal buds die, leading to rosette effect in top of plants; older leaves may be thick and leathery
Cold damage
Marginal to complete killing of seedling leaves; damage may be worse in lower parts of the field
Escobilla
Leaves reduced in size, densely crowded in tufts produced by abnormal forcing of axillary buds, creating a witches' broom effect; dead zones in some leaves
Sulfur dioxide injury
Gray green, water-soaked zones in the foliage, later becoming brown to black
Tropical rust
Yellowish brown pustules break through the upper and lower leaf surfaces; sometimes groups of pustules occur on purple zones of dead leaf tissue; infected leaves tend to drop prematurely
DARK
Anthracnose
Small dark spots on cotyledons or hypocotyls, which in damp weather may spread to the entire seedling and kill it
Phosphorus deficiency
Abnormally dark green leaves; dwarfing
GRAY
Sulfur dioxide injury
Gray green, water-soaked zones in the foliage, later becoming brown to black
GREEN
Areolate mildew
Angular infected spots, pale green on upper surface, covered with dense white masses of mildew growth on lower surfaces, appearing toward end of growing season
Blue disease
Apical leaves bulge toward the base; leaf blade at first light green; entire leaf later becomes deep bluish green; symptoms occur only on parts of the plant that develop after infection is initiated
Leaf crumple
Leaf tissue between veins grows excessively, causing cupping and a blistered appearance; bracts and flowers show distortion; symptoms most severe on new growth arising from ratooned cotton
Leaf curl
Thickening of small and large veins; finlike outgrowths from veins
Phosphorus deficiency
Abnormally dark green leaves; dwarfing
Phyllody
Leaves distorted into stringlike or straplike shapes
Sulfur dioxide injury
Gray green, water-soaked zones in the foliage, later becoming brown to black
Vein clearing
Green color disappears from leaf veins; deep green bands later appear along main veins; young leaves tend to cup downward
LIGHT
Potassium deficiency
Yellowish white foliar mottling; light spots take on a rusty appearance; premature defoliation
ORANGE
Southwestern cotton rust
Orange, pointlike eruptions on upper surface of cotyledons; clusters of orange cuplike structures on lower surfaces
PINK
Anthracnose
Dead areas circular or irregular in outline; with continued damp weather, areas enlarge to consume large parts of the leaf; may form moldlike growth and pinkish slimy masses of spores on surfaces of older lesions
Anthracnose
Dark brown cankers on stem, older ones showing mold growth on the surface, often with pustules full of slimy pink masses of spores
PURPLE
Magnesium deficiency
Reddish purple leaves, veins remaining green
Minor leaf spots
Small dead spots up to 3 mm in diameter, variously colored, often with purplish margins, usually appearing on senescing plants
Tropical rust
Yellowish brown pustules break through the upper and lower leaf surfaces; sometimes groups of pustules occur on purple zones of dead leaf tissue; infected leaves tend to drop prematurely
RED
Alternaria leaf spot
Nearly circular leaf spots up to 6 mm in diameter, with reddish brown dead centers and dark brown margins
Magnesium deficiency
Reddish purple leaves, veins remaining green
Misuse of arsenicals
Reddened foliage, especially at margins of leaves where spray collects
Nitrogen deficiency
Yellowing, eventual reddening of foliage; plants may be dwarfed
TAN
Fusarium wilt; Verticillium wilt
Plants dwarfed; foliage exhibits patterns of chlorotic mottling; daily wilting, with nightly recovery of plant turgor; woody part of roots, stems, petioles, and often peduncles of flowers and fruits discolored with streaks of yellow, tan, gray, or black
WHITE
Areolate mildew
Angular infected spots, pale green on upper surface, covered with dense white masses of mildew growth on lower surfaces, appearing toward end of growing season
Bacterial blight
Water-soaked, angular dead areas in the leaf blade or along principal veins; diseased areas may be coated with slimy bacterial exudate; dead areas turn dark brown and dry, leaving exudate as white waxy crusts on leaf surface
Potassium deficiency
Yellowish white foliar mottling; light spots take on a rusty appearance; premature defoliation
Powdery mildews
Dense accumulation of white mildew and spores on upper or lower leaf surface; leaves are sometimes curled and defoliation may ensue
YELLOW
Fusarium wilt; Verticillium wilt
Plants dwarfed; foliage exhibits patterns of chlorotic mottling; daily wilting, with nightly recovery of plant turgor; woody part of roots, stems, petioles, and often peduncles of flowers and fruits discolored with streaks of yellow, tan, gray, or black
Compaction of soil in root zone
Poor root development; dwarfed plants; wilting during drought stress
Lance nematode
Foliar chlorosis and stunting, sometimes followed by defoliation
Manganese toxicity
Crinkled, distorted leaves; shortened internodes; and dwarfing, all tending to be severe in very acid soils
Misuse of substituted urea compounds or triazines
Yellowing, mottling, and death of young seedlings
Mosaic
Chlorotic mottling and cupping of foliage
Nitrogen deficiency
Yellowing, eventual reddening of foliage; plants may be dwarfed
Potassium deficiency
Yellowish white foliar mottling; light spots take on a rusty appearance; premature defoliation
Reniform nematode
Plants severely stunted; foliage sometimes chlorotic; plants may wilt; small feeder roots destroyed; yield often reduced as much as 60%
Sulfur deficiency
Yellowing of top leaves; lower leaves remain green
Tropical rust
Yellowish brown pustules break through the upper and lower leaf surfaces; sometimes groups of pustules occur on purple zones of dead leaf tissue; infected leaves tend to drop prematurely
No Distinct Discoloration
Acromania
Abnormally upright habit of growth; upper branches barren
Hail damage
Plant laceration and crushing
Flower
TAN
Fusarium wilt; Verticillium wilt
Plants dwarfed; foliage exhibits patterns of chlorotic mottling; daily wilting, with nightly recovery of plant turgor; woody part of roots, stems, petioles, and often peduncles of flowers and fruits discolored with streaks of yellow, tan, gray, or black
YELLOW
Fusarium wilt; Verticillium wilt
Plants dwarfed; foliage exhibits patterns of chlorotic mottling; daily wilting, with nightly recovery of plant turgor; woody part of roots, stems, petioles, and often peduncles of flowers and fruits discolored with streaks of yellow, tan, gray, or black
Fruit
BROWN
Bacterial blight; Anthracnose; Various fungi
Decays of various colors, mostly caused by species of molds, attacking bolls in different stages of development, destroying them partly or completely, or preventing proper opening of the boll or fluffing of the lock
TAN
Fusarium wilt; Verticillium wilt
Plants dwarfed; foliage exhibits patterns of chlorotic mottling; daily wilting, with nightly recovery of plant turgor; woody part of roots, stems, petioles, and often peduncles of flowers and fruits discolored with streaks of yellow, tan, gray, or black
YELLOW
Fusarium wilt; Verticillium wilt
Plants dwarfed; foliage exhibits patterns of chlorotic mottling; daily wilting, with nightly recovery of plant turgor; woody part of roots, stems, petioles, and often peduncles of flowers and fruits discolored with streaks of yellow, tan, gray, or black
Bacterial blight; Anthracnose; Various fungi
Decays of various colors, mostly caused by species of molds, attacking bolls in different stages of development, destroying them partly or completely, or preventing proper opening of the boll or fluffing of the lock