Cotton is called the back-bone of Pakistan's economy.
It is one of the most important fibre and cash crop, which accounts
major contribution in foreign exchange earnings for the country, through
the export of raw cotton and cotton products. It also provides raw
material to local domestic cotton industry. About 40% labour force of
the country is employed in cotton fields and cotton processing mills. It
has 85% share in the total vegetable oil produced in the country, on the
other hand, an important by-product 'cotton seed cake', is valuable
source of protein for ruminant cattle.
Cotton production practices adopted by farmers play
an important role for increased per acre yield. The crop has maximum
area in Punjab followed by Sindh and very negligible in NWFP. The yield
per hectare of seed cotton in Punjab is more to that of Sindh province.
The area, production and yield have been showing an increasing trend
since 1947. The increase in production is due to increase in yield per
acre rather than increase in area. However, during some years, the
production and yield have shown considerable fluctuation, the causes may
be many more, but a disease 'cotton leaf curl' could not be ignored,
neglected and or regretted, because it also cause variable loss time by
time to the crop.
The crop record revealed that cotton leaf curl virus
(CLCV) found to be most important disease, considered as most severe and
destructive. This disease causing virus was first time recorded in
Nigeria (1912), Sudan (1924), Tanzania (1926), Philippine (1959). In
Pakistan, it was first time recorded in 1967 at Multan (Punjab) on some
cotton plants. It was a miner disease until 1987, but in 1991-92, it
becomes severe and since 1992-93 causing a huge production and monetary
loss to the nation. In Sindh, this disease was first reported during
1996 at Ubauro, district Ghotki, and is reached up to New Saedabad,
district Hyderabad, during 1999-2000. It is quite difficult to present
accurate estimates of the losses due to cotton leaf curl disease,
because the losses vary from year to year and from one area to the
other. Sometimes the cotton fields have been found to show as much as
100 percent damage. It is becoming obvious that now, it is up to the
cotton growers and crop protectionists, to design and formulate ways or
mean to combat all enemies of the crop, so that the losses may be
The cause, symptoms, preventive and curative control
measures of cotton leaf curl virus disease, are being summarised here
under, for the benefit of the cotton growers, as a reminder for
researchers so that they could plan their future strategies and for
extension workers so that they may to be alert.
disease is caused due to cotton leaf curl bigeminivirus (CLCV), belongs
to Gemini group, sometimes refer as Gossypium virus 1.
HOST RANGE: More than 60 different crop, weed and
ornamental plants are reported as host of disease causing virus.
Cotton, lady's finger, tomato, chilli, cucurbits (especially water
melon), beans, sunflower, sesame, soybean, cow peas, egg plant (brinjal),
sun kukra, china rose, thorn apple (dhatura), mint (podina), holly hock
(gul-e-khera), Zinnia, AK (Calotropis), shesham (talhi) and citrus
species are sometimes found seriously affected by the disease.
The disease transmitted by feeding of the white fly, Bemisia tabaci (Fig
1) 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 species.
The disease causing virus survives in several different plant hosts,
from which it may spread.
Upward and downward curling of leaves accompanied by small and main vein
thickenings (SVT & MVT) on leaves, pronounced on underside (Fig 2).
If a diseased leaf is viewed from beneath against the light, thickened
vein found darker green and opaque than normal. In extreme but not in
frequent cases, formation of cup shaped or leaf laminar (veins)
outgrowth called "enation" appears on the back or underside of
the leaf (Fig 3). The newly produced leaves are small, excessively
crinkled and curled at the edge. Primary stem often tends to grow taller
than normal. The internodes being elongated and irregularly curved but
sometimes the whole plant is stunted. The flowers checked in growth and
become abortive. The bolls remained small in size and failed to open.
All parts of badly hit plants are very brittle and ready broken.
Use of proper cotton production technology is economical and most
effective for management of all diseases (including this). Therefore,
following disease management practices may help to save the crop from
CLCV as well as other major and minor diseases of cotton.
of disease resistant variety is only safe measure.
(okra), sun kukra, china rose, thorn apple (dhatura), mint (podina),
karund, cucurbits (especially water melon), beans, tomatoes, tobacco,
chillies, 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, during and
after cotton cropping season. Cotton growing zones may play a better
role for this purpose.
*The disease (CLCV)
is not seed transmitted but use of healthy seed, acid delinting and
chemical seed treatment is recommended as preventive measure. The seed
treatment with suitable insecticides helps to reduce the whitefly
(vector of virus) population in the beginning and also help the plant to
gain vigour for averting the damage by virus.
including collection and burning of plant debris may help to control
disease, because disease inoculum (the virus) may also survive through
plant debris. Therefore, the cotton stubs should be removed from the
field just after last picking, because sprouts from diseased plant stubs
provide inoculum for transmission of the disease.
ploughing with short duration, at least two months before sowing, help
to control weeds, which other wise will serve as alternate host of
with non-host crops is useful.
cropping with alternate host crops of the virus (for example Lady's
finger (okra or bhindi) and sesame or tir/til), specially, inter
cropping of cotton in orchards may be avoided.
*Proper use of
irrigation and chemical fertilisers improves the disease resistant power
in cotton plants.
vigorous plants of cotton should preferably be kept at the time of
whitefly play a role to transmit the cotton leaf curl virus from
diseased plant to healthy one, hence whitefly must be controlled through
various possible methods, including cultural practices and using proper
insecticides. The whitefly found most active before sun rise, therefore
the spraying should be done at least one hour before sun rise.
Meanwhile, use of proper cotton production technology
as per recommendations of agricultural experts or 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.