| COTTON TECHNICAL | |||||||||||||||||
|
Introduction
India grows on a commercial scale, varieties falling under all the four cultivated species of Gossypium, viz. G. hirsutum, G. barbadense, G. orboreum and G. herbaceum. The predominant species cultivated is G. hirsutum. Cotton research and development efforts are directed towards progressively increasing the area under G. hirsutum and replacing, as far as possible, the area under the old world species. India is a pioneer in the world in development and commercial cultivation of cotton hybrids. Starting with hybrid H 4 in 1968, hybrid cotton has become extremely popular in central and southern states. Both public sector – and private sector – bred cotton-hybrid seeds are marketed in India. These are based on G. hirsutum x G. hirsutum,, G. hirsutum x G. barbadense and G. hirsutum x G. arboreum crosses predominantly, using conventional hand-emasculation and pollination techniques. In a limited number of tetraploid hybrids, however, use of genetic male sterility or cytoplasmic genetic male-sterility systems is resorted to. Because of increasing labour wages and high cost of hybrid seed production involved in conventional hand-pollination technique a trend to switch over to use of male sterility is now increasing. After the success of H 4 (an intra-hirsutum hybrid between G 67, and well-adapted American extra-long staple cotton variety as female parent, and an exotic variety American Nectariless as male parent), other popular hybrids that followed were: Varalaxmi (an inter-specific G. hirsutum x G. barbadense combination involving Laxmi, an acclimatized American variety, and male parent SB 189 E, a short-branched Russian barbadense type developed at Coimbatore), DCH 32 (export quality interspecific hybrid superior to Varalaxmi) , Asiatic (desi) cotton hybrids DDH 2, G. Cot. DH 7 and G. Cot. DH 9 for rainfed areas in medium- and long-staple fibre categories; H 6, JK Hy 1, TCHB 213, NHH 44, PKV Hy 2, etc. In fact, seventies and eighties can be rightly called as India’s hybrid cotton era with a good tempo in various aspects of hybrid cotton research. During these 2 decades Gujarat, Karnataka, Maharashtra, Tamil Nadu, Andhra Pradesh and Madhya Pradesh have played a key role in developing a large number of cotton hybrids for central and southern regions of the country. For the North zone, particularly for the high-yield potential irrigated tracts of Punjab, Haryana and Rajasthan, the recent identification of intra-hirsutum hybrids like Fateh, HHH 81, Raj HH 6; Asiatic hybrid (intra-arboreum) LDH 11, and a few interspecific hybrids with long staple and early maturity have shown possibility of commercial success of hybrid cottons in north. Among private sector – bred hybrids, prominent ones are MECH 1, MECH 4, and other MECH numbers; MDCH 201, Somnath, Shivnath, Jagannath, ACHH 52 and Ankur series; PAHH 1, Navbharat 1, etc. In fact, during 1993-96, as many as 19 promising hybrids have been released and notified for commercial cultivation in one or the other part of the country. This speaks of high pace of hybrid cotton research and development in India, where it continues to be world leader. In brief, hybrid technology in cotton gained success owing to availability of a wide spectrum of fibre quality, ranging from 30s to 80s counts, availability of useful heterosis (up to 80% for interspecific, and up to 187% for intraspecific), wider adaptability in peninsular India, good seed-production arrangements and greater stability in performance for yield components compared to varieties. However, for developing new hybrids for future, many practical considerations are necessary, both from the cotton grower’s point of view and end-use requirements by the industry. Some of these considerations are: early maturity coupled with suitable morphological and biochemical characteristics to escape insect activity, resistance to new wilt, white-fly and bollworms, development of new cytoplasmic sources and effective restorers to have alternative systems and diversity required for reducing vulnerability of hybrids based on a single source material, discovering or creating new GMS or practically usable male-sterility systems for making Asiatic cotton hybrids, in-depth study of possibility of honeybee pollination or development of mechanical emasculation and pollination techniques, more medium-staple hybrids with high-fibre strength and optimum micronaire value for open-end spinning systems, fibre types suitable for blending, high seed oil content, naked seed and delayed morphogenesis for gossypol gland development supported by other systems of insect resistance, drought-tolerant intra-hirsutum as well as Asiatic (desi) cotton hybrids for sustaining a higher level of productivity in rainfed areas. Interculture in cotton is necessary to create mulch, aeration of the top soil, better intake of water and the control of weeds. Cotton is highly vulnerable to weed competition especially in the initial stage of growth (50-60 days of its growth). Hence control of weeds either by manual labour or by weedicides is essential to get good yield. Dry hoeing with a hand hoe or spade five to six weeks after sowing or before first irrigation is very effective in controlling the weeds. It should be repeated afterwards if necessary. Some weedicides like Basaline and diuron have been found quite useful in controlling the weeds. Basalin at the rate of 1 kg a.i. per hectare in 1000 litres of water should be used as pre-planting spray. It should be well incorporated in the upper soil before sowing of the crop. The cotton crop is attacked by a number of diseases. Some of the common diseases and their recommended remedies are given below:
Cotton crop is subject to attack by a number of insect pests. It constitutes a major limiting factor in cotton production. Predominant loss is caused by the bollworms, viz. American bollworm, the spotted bollworm and the pink bollworm, and sucking pests like jassids and white-fly. Over 50% of the total insecticides used in agriculture go in cotton where pest control accounts for 35-60% of the total cost of cultivation. In many parts of the country, cotton pests are still controlled exclusively by chemical pesticides and as many as 10-20 sprays are common in some parts. The injudicious and indiscriminate use of chemical pesticides in cotton agro-ecosystem has become a matter of concern and alarm due to resultant serious environmental imbalance and degradation. The overuse has led to development of resistance to pesticides, widespread killing of natural enemies leading to resurgence of secondary pests and increased number of pest control failures. The upsurge of cotton whitefly during 1983 to 1987 and unprecedented outbreaks of American bollworm, Helicoverpa armigera (also known as Heliothis) during 1977-78 and 1987-88 in Andhra Pradesh has forced us to take a fresh look on our cotton pest control strategies. This has necessitated the approach towards developing sustainable cotton pest management programmes with minimum reliance on the use of pesticides. The IPM modules made available through research in Punjab. Tamil Nadu, Gujarat, and other states are aimed at the management of cotton jassid, white-fly, aphid, thrips and bollworms. These packages are based on eco-friendly approaches like field sanitation, crop residue removal, mechanical control, crop rotation, trap cropping, pest monitoring with pheromones and conservation and release of natural enemies and ETL-based use of soft chemicals. The IPM technology in cotton includes mass production and large-scale field releases of natural enemies like Trichogramma and Chrysoperla and use of biopesticides such as nuclear polyhedrosts virus (NPV). The sucking pests like whitefly, aphids, Jassids and thrips are kept under check by releasing the predator Chrysoperia carnea twice @ 50,000/ha on 45 and 60 days after sowing and again @ 100,000/ha on day 130. For the suppression of 3 bollworms, viz. spotted bollworm, spiny bollworm and Helicoverpa, weekly field release of a parasitic wasp, Trichagramma chilonis @ 150,000/ha release starting from bud formation stage is recommended. Six such releases are as effective as chemical control. The release of parasite is made after ensuring the presence of host eggs in the field or by monitoring adult population with the help of pheromone traps. If Helicoverpa population is high to that of ETL of 7 second instar larvae per 20 plants, application of biopesticide, Ha-NPV @ 450 LE/ha with 0.5% jaggery and 0.1% detergent is recommended. Mass production techniques for Chrysoperia carnea for control of sucking pests and early stages of bollworms,Trichogramma chilonis for bollworms and Helicoverpa armigera have been standardized. Application of sprayable formulation of gossyplure effectively checked the population of pink bollworm by causing mating disruption and increased the yield by 20%. Use of Neem oil 0.5% + teepol 0.1% and Neem seed kernel extract (NSKE) 5% have been effective against cotton bollworms and sucking pests. Neem seed kernel extract, Neem oil and Neem cake gave good protection against the whitefly. Also, Neem oil at 0.5% mineral oil at 2.0% and fish oil rosin soap at 2.0% effectively reduced the whitefly population with least disturbance to Aphelinid parasites. Resistant varieties against jassids have been evolved. Screening of genotypes for tolerance to pests revealed that IC 1030, RKR 4145, KG 9-18 and S 8/3 have field tolerance to bollworms and IC 625, SRT 1 and B 1007 have field resistance against jassids. G arboreum genotypes exhibited consistently higher level of condensed tannin in young bolls which is linked with resistance to bollworms. The pigmented lines, which are less prone to bollworms attack also possess high levels of condensed tannins. Close spacing, excessive use of nitrogenous fertilizers and intercropping of okra with cotton should be avoided as they have been found to be conducive for sucking pests. Rotation of cotton with non-preferred hosts (ragi, maize or jowar), destruction of alternate weed host plants, manual removal and destruction of flared up squares, damaged and shedded fruiting bodies and adjusting the time of sowing is useful in reducing bollworm incidence. Castor is a good trap crop for Spodoptera litura and intercropping of mungbean reduces the jassids incidence. Cotton intercropped with cowpea has been found to harbour more number of coccinellid predators and other natural enemies. According to the Department of Agricultural Research and Education, ICAR, Government of India, the IPM technology on cotton has been successfully demonstrated in Tamil Nadu, Punjab, Gujarat and Andhra Pradesh through on-farm trials. In Andhra Pradesh, the cost-benefit ratio was higher in IPM plots (1:4.5) compared to non-IPM plots (1:1.15). In Tamil Nadu and Punjab, pesticide use was reduced by 12-73%, yield was increased by 23% and net income per unit area by 31%. Abundance of natural enemies was increased by 3-fold and the cost of insecticide and environmental pollution was reduced by over 50% in the villages under the Operational Research Project. |
