Disease Name

Picture showing disease
symptoms

Causal
organism

Symptoms

Control Measures

Anthra
cnose

Glomerella
gossypii
and
Colleto-
trichum
indicum

All the above ground parts of the plant are attacked; infection on the seedlings and bolls is serious; large red spots appear on the seedlings; later, they girdle the stem and kill it.

Treat the seed
with any
organo-
mercurial
(Agrosan GN,
Ceresan) @
2-2.5 g/kg;
spray the crop
with 1%
Bordeaux
mixture.

Leaf
spots

Helminth-
osporium
gossypii
Alternaria
pp.Mycosp-
haerella
gossypiana,
Myrothe-
cium
roridum

Helminthosporium spots are light brown, circular and numerous, the centre of the spot later turns ashy and falls off, leaving a hole; Alternaria spot is typified by an abundance of papery, rusty brown spots of irregular size and shape; Cercospora leaf spots are small and irregular and have a purple border and a white centre.

Spray the crop with 0.3% fixed copper or 0.2% Zineb.

Grey
mildew

Ramularia
areola

A whitish growth appears chiefly on the undersurface of the leaves.

Spray the crop with 1% Bordeaux mixture or with any fixed copper fungicide, (0.3%)

Powdery
mildew

Leveillula
taurica and
Oidium sp.

White powdery patches appear on the undersurface of the leaves; the corresponding upper portions just above patches become pale and brown.

Dust the crop with finely powdered sulphur @ 15 kg per hectare.

Dry root
rot or
sore
shin

Macro-
phomina
phaseoli

Large brown lesions are formed in the collar region; the vascular zone of the roots is discoloured brown; rootlets rot and the plants dry up.

Practise crop rotation; grow resistant varieties.

Root
rot

Rhizocto-
nia
bataticola
and
R.solani

Plants wilt suddenly; roots rot and show the shredding of the bark; the disease occurs in patches; affected plants can be easily pulled out.

Sow cotton early (1^st week of April) or very late (1^st week of June); practise mixed sowing with moth (Phaseolus aconitifolius) in infected areas.

Wilt

Fusarium
oxysporum
F.
vasinfec-
tum

Leaves yellow and dropping; plants stunted, gradually wilt and die, the vascular tissue become brown; only scattered plants are affected.

Grow resistant varieties.

Verti-
cillium
wilt

Verticillium
alboatrum

The yellowing of cotyledons and stunting; the outstanding symptom is the mottled appearance of the leaves with yellow areas developing between the veins and on the margins; brownish discolouration of the woody stem, which is usually more evenly distributed through the stem centre (stele) and lighter brown than the discolouration caused by the Fusarium wilt.

Grow resistant varieties, spot application of wet Ceresan @ 0.1% (6.5 kg of wet Ceresan per ha before planting).

Sclero-
tial
disease

Pellicularia
rolfsii

A white weft of mycelium is formed near the base of the plant on which white to raddish-tan spherical sclerotia appeared.

Crop rotation and sterilize the soil.

Rust

Cerotelium
desmium

Innumerable, small, yellowish brown rust pustules are formed on the leaves.

The disease is occasionally serious.

Bacterial
blight
(black
arm or
angular
leaf
spot)

Xamtho-
monas
malvace-
arum

All the aboveground parts are attacked; lesions on leaves are angular and water-soaked; they turn dark brown, when old; lesions on the stem are long and dark.

Treat acid-delinted seed with an organo-mercurial (Agrosan GN or Ceresan) at 2-2.5g per kg or Agrimycin-100 (100 ppm), spray with 0.3% copper fungicide; Agrimycin 100 + Copper or Oxycarboxin (1.5-2 kg/ha); grow resistant varieties.

Stenosis
(small
leaf)

Virus

Small leaf is characterized by an extreme stunting of the aerial organs; leaves are variously lobed; flowers very small and bolls are never formed.

Grow resistant varieties.

Tirak (prem-
ature
defect-
ive
openings of the bolls)

Physio-
logical
disorder

The early yellowing; dropping and shedding of leaves; bolls crack; do not open properly; seeds remain immature, lint quality greatly reduced.

Sow late (June); apply extra water at flowering and fruiting on light sandy and alkaline soils.

Red leaf

Physio-
logical
disorder

Occurs on American varieties; leaves turn yellow or red and roll downwards; when severely affected, the whole lamina becomes red leaving the veins green; leaves dry up and are shed.

Proper manuring; growing of resistant varieties.

Seedling Disease

A soft, watery
rot charact-
erizes
seed and seedling disease.

(These disease-
causing organisms attack the young seedling before or after emergence.)

Seed decay, decay of the seedling before emergence, partial or complete girdling of the emerged seedling stems, and seedling root rot. Damaged seedlings are pale, stunted, slower growing, and sometimes die within a few days. R. solani and P. exigua may attack seedlings from the time they emerge until they are about 6 inches tall. After this stage, the stem becomes woody, and subsequent infection rarely occurs unless the stem is injured.

Phoma exigua (Ascochyta), and Fusarium spp.

Cause post-emergence damping-off. Premature dying of cotyledons, which turn brown and shrivel;

Fungicides containing PCNB (Terrachlor) or Iprodione (Rovral) are generally effective against Rhizoctonia solani.

Fungicide effectiveness against P. exigua has not been evaluated.

Use (certified seeds) quality seed with high germination potential.

Plant only fungicide-treated seed. Applied fungicide and seed should be properly layered. protectants fungicides, such as captan or Thiram, Systemic fungicides, such as carboxin (Vitavax) provide temporary protection from certain types of pre-emergence and post-emergence damping-off.

Use an in-furrow granular fungicide (Thimet). Granules should be placed in the bottom of the seed furrow and mixed with the covering soil.

Crop rotations, Proper fertilization, avoid excessive rates and deep incorporation of herbicides, good seedbed e.g. raised beds in early planted cotton are other control measures.

Application
rate
(Gram per
100-ft row)

PCNB (Terraclor)
PCNB+
terrazole
(Terraclor
Super X)

10G,15G,75WP, 2EC

10+2.5G, 15+3.8G

140-250
84-176
22-44
66-110
140-205
110-150

Effective against
pythium and
Rhizoctonia.