Cotton
is one of the most important fiber and cash crops of Pakistan, which
earns foreign exchange for the country. 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.
On a whole, cotton is a major crop in parts of African tropics,
Australia, China, Egypt, India, Mexico, Pakistan, Soviet Union,
Sudan, United States, and warmer regions of central and South America. |
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Archaeologists and historians believe that cotton existed 5000 years ago. Mohan-jo-Daro was nature place of cotton, where the people knew the arts of spinning and weaving. Cotton lint was separated from seed on charkha (a kind of hand cranked roller gin) and the fibers processed in to fabrics with drop spindles and primitive looms. The quality of the textile produced has been excellent (Bhatti and Soomro, 1996 and Khoso, 1992). The history of 'cotton crisis' is also as old as its cultivation. Following poem of Shah Abdul Latif, a saint poet of Sindh can be quoted as first example (during 1689-1752 AD). |
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In the midst of the trees no cotton plants are: So here are no spinners. The empty bazaar Has ensalted my heart; Foolish girl, in your brain. Translated by: H. T. Sorely (1938) |
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The second example
regarding cotton diseases was quoted in Taxas Agricultural Experiment
Station Bulletin No.4 (1888). Palmel studied and wrote about root
rot of cotton (Anonymous, 1981). The struggle against cotton diseases
continued up to date. It had been revealed that this crop was subjected
to more than 60 diseases (Anonymous, 1981). The diseases reduced
the yield and brought about heavy losses. The work carried out so
far in Pakistan shows that seedling rot or wilt, root rot, boll
rot, anthracnose, different types of leaf spot diseases, premature
opening of bolls (Tirak), stunting and reduction in size of leaves,
some nematode species, bacterial blight (angular leaf spot and boll
rot), leaf curl and stenosis of cotton, found causing damage to
the crop (Kamal and Moghal, 1968; Hafiz, 1986 and Jiskani, 1992
and 1999). Such diseases are injurious in some areas, in some years
and on some plant parts. The magnitude of disease damage depends
up on the environment and cultivar. |
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The crop record revealed that root and boll rot diseases of cotton were considered as most severe and destructive, but since last decade, cotton leaf curl virus (CLCV) found to be most important disease. This disease was first time recorded in 1967 at Multan on cotton plants. In Sindh, this disease was first reported during 1996 at Ubauro, District Ghotki. Now it is reached up to New Saedabad, District Hyderabad during 1999-2000. It was considered a minor disease until 1987, but in 1991-92, it infested 35,000 acres and 294,000 acres during 1992-93 causing a huge production and monetary loss to the nation (PARC, 1993). |
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However, it is quite difficult to present accurate estimates of the losses due to diseases. The losses vary from year to year and from one region to the other. The fields have been found to show as much as 100 percent damage in certain cases. 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 minimized. |
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The causes, symptoms, preventive and curative control measures of some important diseases of cotton, are being summarized here under and based on the recommendations by Bhatti and Jiskani (1995 and 1996); Hafiz (1986); Jagirdar and Jagirdar (1980), Jiskani (1992), Kamal and Moghal (1968) and PARC (1993), for the benefit of the cotton growers. |
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Cotton Leaf Curl Virus Cause: The disease causing virus belongs to Gemini group. Symptoms: Upward and downward curling of leaves accompanied by small as well as main vein thickenings (SVT as well as MVT) on leaves, pronounced on underside. If a diseased leaf is viewed from beneath against the light, thickened vein found darker green and opaque than the normal. In extreme but not in frequent cases, formation of the cup shaped or leaf laminar (veins) out growth called "enation" appears on the back or underside of the leaf. The newly produced leaves are small, excessively crinkled and curled at the edge. The primary stem often tends to grow taller than normal. The enter-nodes being elongated and irregularly curved but sometimes the whole plant is stunted. The flowers checked in growth and become abortive. Bolls remained small in size and failed to open. All parts of badly hit plants are very brittle and ready broken. |
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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: 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. Root Rot 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 and shredding. Perpetuation: Disease causing fungi are soil borne, hence it may be claimed that both (fungi and soil) factors are responsible. Minor Diseases 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 so much. Control 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. 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. Reference: 1. Anonymous. 1981. Compendium of cotton diseases. Edited by:
Q. M. Watkins. American Phytopathological Society. |
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