Cotton is a major world fibre crop. It is grown under a very broad range of climates, soils and cultural practices. In Pakistan it was grown on approximately 3.0 million hectares in 2003-04. Prior to the introduction of man-made artificial fibres, it was only a raw material from which human clothing and other necessary textiles were manufactured. It produced about 13.761 million bales of lint (PCGA report by January 2005) and 780 kg of lint per hectare. Cotton provides raw material to more than 337 textile mills, 1500 ginning factories and 5000 oil mills. Approximately 65 percent of Pakistan's annual export income comes from the textile sector.
Similarly, other industries, such as pharmaceutical, soap, chemical and feed industries also rely on cotton by-products. Besides this, cotton is an occupation of 1.5 million farming families and provides job to 50-54 percent of the labour force. Therefore cotton is known as the life blood of Pakistan's economy.
Pakistan's consumption of cotton for the year 2003-04 was 9.6 million bales (of 480 lbs), whereas the production was 8.2 million bales (of 480 lbs), this indicates that we are still getting a low yield. The average per acre yield of our country is about 256 kg per hectares, whereas our local varieties have a potential to produce about 910 kg per hectare. So to achieve this target potential yield, the cotton growers should come up with modern agricultural practices, especially crop protection and secure storage techniques for maintaining the quantity and quality of yield as well.
No doubt the growers aim to ensure the maximum yield with minimal adverse impacts, but there are several factors which cause their economically unacceptable damage. Unfortunately in our farming systems, uncontrolled insect pests, diseases and weeds reduce yields at harvest by 30-50 percent and around 20-25 percent during storage.
Among yield decreasing factors, at present plant diseases are the major concern. Generally a heavy disease infestation may cause crop losses by 30-50 percent, but under some specific conditions 100 percent losses are also observed.
COTTON LEAF CURL VIRUS: Since the last two decades Pakistan's economy is facing a similar disastrous threat in the form of a cotton disease known as the cotton leaf curl virus (CLCuV). CLCuV gives sleepless nights to cotton growers. Due to its devastating effects, the growers plowed thousands of acres of the standing cotton crop, the rising graph of cotton production thus greatly declined.
The fatal CLCuV, a viral disease of cotton, was first recognised in 1912 in Nigeria with the common symptoms of small vein thickening and upward curling leaves. Later on it was reported from Tanzania in 1926 and from Sudan in 1934.
In Pakistan, it was first reported in Multan (Punjab) in 1967. This disease again reemerged in 1988 in Multan in Mauza Balail, where some foreigners were working on an insecticide project. Initially, only 150 acres were reported to be affected but next year this disease spread to about 500 acres. Serious notice was taken only in 1991 when a large area of about 35000 acres was reported to be affected, and huge yield losses occurred after a record crop (12.8 million bales) in 1991-92 and decreased to 8-9 million bales per year in the next two years. In Punjab in over an area of 6 million acres, the crop yield dropped from 343 kg per acre to 199-232 kg per acre. Total loss due to this disease for three years (1992-93 to 1994-95) was estimated to be about three million bales which was valued at rupees 30 billion.
This disease again appeared in the form of "Burewala virus" in the Burewala of the Vehari district of Punjab in 2001-2002. The virus had 92 percent of the same characteristics as that of the scientifically called 'geminivirus'. Almost all cotton varieties, including those claimed as CLCuV-resistant also came under the CLCuV attack. Hot spots of CLCuV with varying degrees of economic injury levels were found in almost all the cotton districts of the Punjab, especially Vehari, Rahim Yar Khan, Dera Ghazi Khan, Bahawalpur, Multan, Lodhran, Muzaffargarh and the Layyah districts. As a result, to curb the problem, the Punjab Government put a ban on the cultivation of any CLCuV-susceptible variety in Punjab including the NIAB-78, which is the most popular and most stable cotton variety with an excellent performance.
In Sindh, this disease was first reported in 1996 at Obauro (District Ghotki) and the Khairpur District. Afterwards, it was expanded to some areas of Nawabshah and the Hyderabad districts. In the year 2002, the total area affected by CLCuV was reported to be 10-15% in northern Sindh. Now it has reached up to almost all the cotton growing districts, though with minor intensity, but it is still a major threat to our economy.
CAUSES AND SYMPTOMS: This is a viral disease, and the virus causing the disease belongs to the Gemini group. Generally there are 21 viruses which are associated with cotton (Gossypium hirsutum). They are namely the Abutilon Mosaic Virus, Acromania, African Cotton Mosaic, the Cotton Anthocyanosis Virus, Cotton Blue Disease virus, the Cotton Leaf Crinkle, the Cotton Leaf Crumple Virus (CLCrV), the Cotton Leaf Curl Virus (CLCuV), the Cotton Leaf Mottle, Cotton Leaf Roll virus, the Cotton (common) Yellow Mosaic, Cotton Yellow Vein (CYV)/(Texas Vein-clearing), Flavescence, flower virescence (phyllody), Indian Leaf Crumple, Infectious Variegation, Murcha vermelhao/purple wilt, Stenosis (small leaf),Terminal Stunt ,Tobacco Streak and Viral Wilt.
The prominent symptoms of CLCuV are stunted crop growth with small and dark green thick coriaceous leaves which curl upwards or downwards along with the thickening of the mid rib. In a severe attack, a small cup shaped leaf-like structure, called "enation" is developed on the back of leaves. No or small bolls formation occur which fail to open.
Besides CLCuV, a minor infestation of cotton leaf crumple virus (CLCrV) disease is also observed in Pakistan. This disease was first reported in the irrigated desert south-west in 1950.
CLCrV symptoms are distinguishable from CLCuV symptoms in that the infected leaves curl downward accompanied by interveinal hypertrophy and foliar mosaic.
Both the CLCuV and CLCrV are whitefly (Bemisia tabaci)-transmitted and belong to the subgroup III geminiviruses. However, little information is available on the relationship of these two viruses with each other and with other subgroup III geminiviruses.
POSITION OF COTTON VARIETIES: The quality seed is a vehicle of technology through its genetic composition and heads to successful production across the agro-ecological condition. The availability of quality seed of crop varieties continues to be a problem of major concern for Pakistan's agriculture.
There had been a long series of cotton varieties released from various cotton research institutions, but none of these could find acceptance with cotton growers. Only the NIAB-78 which occupies approximately 80% of the cotton area, due to its stability and high yield potential since its year of release in 1982, happens to be the cotton variety most acceptable to farmers and suits the farming system of the country. Pakistan, therefore, revolves around only one variety i.e. the NIAB-78. However, it is not resistant to the cotton leaf curl virus (CLCuV). Due to its susceptibility to CLCuV, the Punjab Government has put a ban on its cultivation.
Though various agricultural research institutes have developed more than 50 registered cotton varieties upto 2003, most of them are susceptible to CLCuV and some are not available in such a quantity to meet the home demand.
Recently some varieties were developed within a very short period and are claimed as CLCuV resistant. A variety, CIM-473 was marked out as being CLCuV-resistant but, according to a report of the Directorate of Pest Warning and Quality Control of Pesticides, this variety was under CLCuV attack in most of the cotton belt, including Multan, Khanewal, Vehari, Pakpattan. Other preferred cotton varieties like CIM-446, FH-900 and FH-901 are also reported with the same problem. Currently, there seems to be no variety fully resistant to the CLCuV disease, consequently CLCuV-resistant varieties need to be evolved which are otherwise similar in characteristics, and preferably high yielding than the most popular variety i.e. NIAB-78.
MANAGEMENT OPTIONS: 1-The continued use of CLCuV-susceptible varieties without any programme of their replacement constitutes a major risk for cotton production in Pakistan. So a premier focus should be given to eliminate the CLCuV disease and a well-planned programme of evolution and introduction of CLCuV-resistant varieties of desired characteristics must be in place to gradually replace the existing CLCuV-susceptible varieties. This is only the sole and the most promising and least expensive method of disease suppression.
2- The federal government has allocated a sum of Rs 149.1 million for the development of CLCuV resistant cotton varieties. For this task four federal research institutions; Central Cotton Research Institute (CCRI) Multan, CCRI Sakrand (Sindh), Nuclear Institute of Agriculture and Biology (NIAB) Faisalabad and Nuclear Institute of Biology and Genetic Engineering (NIBGE) Faisalabad have been selected. But to achieve the objectives a period of some twelve long years is required to evolve a new cotton variety after cross-breeding repeatedly. Currently, there seems to be no variety fully resistant to the disease therefore the government needs to pay urgent attention to take preventive measures against this disease for the next crop.
3- In the absence of CLCuV-resistant varieties, the immediate solution for eliminating or reducing the menace of this disease lies in the adoption of modern agricultural practices. The destruction of the host plants (all weeds, especially broadleaved and stub cotton plants), the avoidance of susceptible alternate host crops (as okra, sesame, egg plant, water melon, sun kukra, china rose, thorn apple (dhatura), mint, karund, cucurbits, beans, tomatoes, tobacco, chilies, soy bean, sun flower, cow peas, holly hock, zinnia, sesame, citrus species etc.) and proper agricultural practices; such as proper irrigation, soil and fertilisers management, excellent weed control.
4- Whitefly, Bemisia tabaci (Genn.) has been reported to transmit the CLCuV, therefore its early and effective control should be ensured by applying the recommended pesticides and with the cultural practices of deep plowing, clean cultivation, seed treatment with proper fungicide, adequate manuring, proper plant spacing, judicious irrigation, balanced and timely use of fertiliser (especially nitrogenous fertilisers) to discourage the whitefly build up and reduce the risks of infection.
5- The use of potassic fertilisers and the foliar application of micronutrients, especially zinc and boron at various growth stages, as the seen by the writer during several field trails, have proved quite beneficial for eliminating or reducing the menace of the virus.
6- The application of hot air or heat treatment by burning plant wastes in CLCuV-affected fields, and top pruning of the affected plants are also found to be helpful in reducing virus deterioration.
As cotton is the mainstay of Pakistan's agrarian economy, and has a major share (about 60%) in the foreign exchange earnings, therefore all embracing efforts are essential to cope with the present situation which is fast deteriorating year after year. Top experts should be included to finalise the steps that are needed to be taken by the farmers. Thereafter, the Agriculture Extension Department must educate the cotton growers and make them aware of those essential steps which must be taken before the cotton sowing season sets in. All the necessary action must be taken in a steadfast manner to ensure the damage is stopped or reduced to an endurable level.
It is the responsibility of the cotton growers to adopt modern agricultural techniques for the development of the country.