Transmission: The disease transmitted by feeding
of the white fly, Bemisia tabaci with in 6.5 hours. A single female,
carrying virus can infest many plants. It may also be kept in
mind that white fly is known to survive on as many as 53 host
plant species, and is responsible for transmitting 23 crop diseases
in region. At global level, white fly infests 600 different plant
Cause: Aspergillus niger, Fusarium oxysporium,
Rhizopus oryzae (belongs to fungi) and a bacterium Xanthomonas
malvacearum reported as predominant causes of boll rot.
Symptoms: The research studies revealed that
four different types of symptoms may occur, which can be distinguished
on the basis of their specific casual agent, as below:
Black boll or Aspergillus rot: Affected bolls start losing green
color altogether, become pinkish brown and finally sooty black
due to over growth of fungus.
Rhizopus rot: Infected portions become grayish along with softening
of internal tissues. The fungus grows abundantly and covers many
bolls under moist conditions.
Fusarium rot: The bolls become dried with color assuming reddish
and brownish tinge and showing dry and white fluffy fungal growth
inside the bolls on opening.
Bacterial or Xanthomonas rot: Water soaked areas developed on
the bolls giving out gummy substance and foul smell.
Perpetuation: Diseased plant debris and seeds
carry over the disease causing organisms. Humid conditions after
rain and speedy wind favor the spread and severity of boll rot.
Sometimes, different boll worms also play a role, to transmit
disease, from infected to healthy bolls/ plants.
Angular Leaf Spot or Bacterial Blight
Cause: A bacterium Xanthomonas malvacearum cause
angular leaf spot or bacterial blight or boll rot of cotton.
Symptoms: The disease attacks all parts of the
plant above ground level, at all stages, causing seedling rot,
angular spots on leaves and stems (sometimes called black arm
disease) and boll rot (as already mentioned). In initial stages,
water soaked lesions (spots) appears on lower surface of the leaves.
Later on, these spots increase in size, turn brown to black, becoming
necrotic, angular and are visible on the upper surface. These
spots vary in size and then coalesce, forming irregular patches
and giving rise to gummy bacterial exudates. Heavily infected
leaves turn yellow and drop down. The disease produces elongated
black lesions on the stem, branches and petioles. Stems show cracking
and gummosis (gummy substance) and are easily broken, even by
wind. Bolls are marked by the appearance of water soaked lesions,
which are dark brown to black, invariably sunken, results in reduced
boll size, poor production of lint and loss in viability in seed.
Perpetuation: Infected seeds and plant debris
act as a source of infection, but can also spread through irrigation
water, rain splashes, wind, insects and contaminated field implements.
Cause: The fungi Macrophomina phaseoli, Rhizoctonia spp., Fusarium
spp. etc. are predominantly isolated from diseased roots.
Symptoms: The disease affects the roots exclusively,
causing pre-wilt shedding of leaves, yellowing of foliage, disintegration
of root tips, discoloration and shredding of roots, exudation
of drops of smelly liquid from the rotted plant parts. Mostly,
wilting of shoots occur in only few diseased plants, which ultimately
results in the death of entire plant. This disease generally appears,
when plants are about 4-6 weeks old and continue up to boll formation.
Diseased plants can be easily pulled out of the soil, appears
in patches. Roots and root-lets show rotting, yellowing, disintegration
Perpetuation: Disease causing fungi are soil
borne, hence it may be claimed that both (fungi and soil) factors
Anthracnose, leaf spots (caused by different fungi), sooty mold,
stenosis, stunting and premature opening of bolls (Tirak) etc.
are also reported to cause disease in cotton and damage to the
crop, which may reduce the yield, sometimes very low and sometimes
Following disease management practices may help to save the crop
from all above major and minor diseases of cotton.
* Cultivation of disease resistant variety is only safe measure
of all different diseases.
* Eradication including collection and burning of plant debris
may help to control seedling, root and boll rots as well as bacterial
blight, because disease inoculum may also survive through plant
" Deep plowing with short duration, at least two months before
sowing, help to control seedling and root rot.
" Proper land leveling is a preventive measure against seedling
and root rot.
" Use of healthy seed, acid delinting and chemical seed treatment
minimize the disease incidence of seedling, root and boll rots
as well as bacterial blight.
" Crop rotation with non-host i.e. sowing of sorghum for
3 to 4 years is useful for control of seedling and root rot.
" Mixed cropping with kidney bean or fodder and leguminous
crops saves the cotton crop from root rot.
" Proper use of irrigation and chemical fertilizers improves
the disease resistant power in cotton plants.
" Early sowing of crop is preventive measure for control
of boll rot.
" White fly transmits cotton leaf curl virus from diseased
plant to healthy one, whereas, different cotton boll worms may
play a role to transmit the boll rot diseases, hence white fly
and boll worms must be controlled.
" Lady's finger (okra), sun kukra, china rose, thorn apple
(dhatura), mint (podina), karund, cucurbits (especially water
melon), beans, tomatoes, tobacco, chilies, soy bean, sun flower,
cow peas, egg plant (brinjal), holly hock (gul-e-khera), zinnia,
sesame, Ak (Calotropis), shesham, citrus species etc. are recorded
as alternate host plants of cotton leaf curl virus as well as
white fly, and also some of them are alternate host of boll worms.
Therefore, they all must be eradicated before and during cotton
cropping season. Cotton growing zones may play a better role for
Meanwhile, use of proper cotton production technology as per
recommendations of agricultural experts/researchers is economical
and most effective for cotton disease management. It is out look
and responsibility of the cotton growers to adopt the modern cotton
production technology and play a role for the development and
prosperity of the country.
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