Sunday, June 20, 2010

Sericulture ,Cocoons,silkworms,mulberry leaves

Sericulture

Sericulture is an agro-based industry. It involves rearing of silkworms for the production of raw silk, which is the yarn obtained out of cocoons spun by certain species of insects. The major activities of sericulture comprises of food-plant cultivation to feed the silkworms which spin silk cocoons and reeling the cocoons for unwinding the silk filament for value added benefits such as processing and weaving.SERICULTURE, the technique of silk production, is an agro-industry, playing an eminent role in the rural economy of India. Silk-fibre is a protein produced from the silk-glands of silkworms.
Historically, sericulture was introduced for the first time, into China by Hoshomin, the Queen of China. For a long time, sericulture was considered to be a national secret by the Chinese Government, and as an industry it was not known in other countries. Later, it was introduced into Europe and Japan as well. According to reports available, sericulture was introduced into India about 400 years back and the industry flourished as an agro-industry till 1857, with an annual production of two million pounds of silk fibre. The industry survived the onslaught of the Pebrine disease during the period from 1857 to 1895. However, after 1928, the sericulture industry showed a decline in its production owing to the fierce competition from advanced sericulture countries, such as Japan, China and European countries. After the Independence, the industry is flourishing as an agro-industry, giving employment to over 3.5 million people in the Country.
The annual production of silk in the world is estimated at 45,000 tonnes of which Japan and China contribute 18,936 and 13,200 tonnes respectively. South Korea, USSR and India are the other leading sericultural countries in the world. The industry has survived the stiff competition with the man-made fibres and it is now estimated by the Food and Agriculture Organisation of the United Nations that the total requirement of silk by 1980 would be of the order of 80,000 tonnes, leaving a demand of 35,000 tonnes. Japan, which is the premier silk-producing country, owing to its recent industrialisation, high cost of labour and the shortage of land available foe mulberry cultivation, has its limitations in increasing its production. Further, owing to heavy internal consumption, Japan has become an importer of silk, thus widening the gap between production and demand. This situation has given a boost to the sericulture industry in the developing countries, e.g.India and South Korea.
Among the developing countries, India enjoys a very favourable position for doubling the present status of of silk porduction of 2,969 tonnes owing to the low cost of labour. sericulture is ideally suited for improving the rural economy of the country, as it is practised as a subsidiary industry to agriculture. Recent research has also shown that sericulture can be developed as a highly rewarding agro-industry.
In India(Karnataka state), where the temperature ranges from 16-31 degree centigrade, enjoys favourable climatic conditions for rearing the silkworm Bombyx mori throughout the year, whereas in West Bengal, the multivoltine silk-worm rearing is practised even under adverse conditions of temperature. In Jammu & Kashmir, the rearing of silkworms is practised once a year during May-June.
Of a life span of 50 days of B.mori, the egg stage lasts 10 days, the larval stage lasts longest-25-30 days. The pupa stage takes 10 days. The silkworm pass 4 moults during growth. The total quality of leaf required to raise a unit of 40,000 larvae(100 dfls) is 500-600 kg by using the traditional methods. The silkworms consume as much as 95% of the food after the third & fourth moults. At the end of the larval duration, the silkworm emits silk from its mouth & constructs a cocoon on a scaffolding. The cocoons produced by hybrids are used for extracting the silk fibre. For preparing the hybrid silkworm eggs, pure races of silkworms are raised in seperate areas. The cocoons are preserved properly in the egg-producing factories, popularly called silkworm grainages. the moths are allowed to emerge. The selected combination of moths are allowed to copulate for 4 hrs. The male after the first copulation is either rejected or used for copulating with another female. Later, the female is consigned to a dark plastic 'cellule'. She lays about 400 eggs in 24 hours. At the end of 24 hours, the female is crushed & examined for hereditary diseases. Only certified disease-free hybrid eggs are reared for industrial silk production.
Considering the various factors, such as the place of origin,voltinism, the colour of the cocoons, the larval markings, the colour ,shape & size of cocoons,the silkworms are classified into different breeds. The multivoltine races & their hybrids are reared in West Bengal & Karnataka. Owing to the non-diapausing of the eggs & the copious growth of the mulberry, these breeds can be reared six times & the cocoons are harvested after 2 months. These multivoltine hybrids have a short larval duration & are generally poor yielders of cocoons. Bivoltines, because of the interruption of diapause, can have only 2 life-cycles a year. However, its possible to break the diapause artificially by treating 1-day old eggs in Hydrochloric acid of 1.064 specific gravity at 46.1 degree centigrade. By adopting this technique, it is possible to take more than 4 crops in a year. Univoltines & bivoltines require more leaves than multivoltines. However, the yield & quality of the cocoons are superior to those of multivoltines. The multivoltine silkworms yield about 25 kg of cocoons per 40,000 eggs reared, whereas the bivoltines yield 40 kgs. The average annual yield of cocoons in India is as low as 150 kg under rainfed conditions, & under irrigated conditions, it is about 400 kg.
Strict Buddhists refrain from wearing or using silk products, as the silkworm pupae are killed in the process of making silk. Animal activists say that the practice of boiling cocoons in hot water for silk is cruel.


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