12th Class Biology Domestication of animals. For enhancement of Food production Sericulture

Sericulture

Category : 12th Class

Sericulture is the breeding and management of silk worms for the production of silk. It has been practiced in India since second era or century B.C. The silk which is produced by silk worm is of a valuable natural protein fibre. Silk worms are the larvae of silk moths. The rearing of silk worm for the production of silk is known as sericulture.

History of silk : Historical account of use of silk and rearing of silk worm eggs, larvae and cocoons are available from china. It was Lotzu the empress kwang-Ti who for the first time discovered the silk thread and its source the silk worm cocoon. The technique of sericulture was kept as a secret by the chines people. In about 550 B.C. The sericulture technique was diffused to European countries. The available mythological literature deals with facts rearing the use of silk in ancient India. By about 1000 A.D. the sericulture was in practice in China, Europe and India, China was the leading country in this field.

At present the sericulture is practiced in China, Japan, Korea, India, Brazil, Russia, France and Italy. Some of the south east asian countries. China is topmost country producing some 48% cocoons and 40.9% of raw silk. Next biggest silk producing country is Japan, India is placed in third position as for as the production of silk in term in quantity is concerned.

Silk in India : As far as silk as a fabric is concerned it is a matchless fabric second to none. Therefore, silk garments have been a favourite choice since ancient times. Use of silk clothes finds its mention from pre-historic period. There are description of use of silk clothes from vedic period. In Ramayana and Mahabharat period the silk clothes adored the bodies of royal princess, prince, kings and queens. It attire of the rich people. The silk clothes were used to the superiority of social and economic status. It was given in gifts by rich people and royal families.

In the medieval period the silk was a recognised commodity of commerce. The silk clothes and raw silk were imported from China and Japan. Later on it was also imported from Europe. By the Moghul period India had a rich heritage of silk clothes. The silk was imported as raw silk. It was spun into silk thread and silk clothes were woven in handlooms silk clothes became almost a craze among royal families and rich persons. A number of such looms were in operation in Banaras, and different parts of Uttar Pradesh, Kashmir became centres for the production of cocoons and rearing of silk worm. Sporadic silk textile centres were also present in South India. It was in 1905-1906 that a scientific investigation in the field of sericulture was undertaken in India by the Indian Institute of Agricultural Research at Pusa, New Delhi. It was Lefroy who conducted research on the silk worm and potentialities of silk production in India. A series of exhibitions were organised to popularize silk and attract the attention of scientists and industrialists as well towards sericulture in India.

By 1910 India started regular production of raw silk. The rearing of Bombyx mori and Autheraea species was undertaken. Silk textile industry was finally established in Kashmir, U.P. and Karnataka. Silk garments were exported by this time. Silk clothes from Bengal, Banaras and karnataka were famous even in the European markets.

Silk in Modern Age : Sericulture as well as silk industry is firmly established in India. India at present is the third biggest country in the field of silk production and only next after China and Japan.

The reasons for the poor growth of sericulture in India were:

(1) High cost of production.

(2) Low yield.

(3) Poor quality of raw silk.

But the recent efforts by the Government of India and various state governments such as research in sericulture and training in sericulture technique, development of silk worms marketing facilities and cultivation of plants, e.g. Morus indica or shahtoot Norus alba or 'Toot' castor sal etc. Central Sericulture Station, Berhampore, Central Research and Training Centre, Mysore and Ranchi have been established. Various states have undertaken a programs of research, training and plantation of host plants under their rural development programs. As a result of these efforts new varieties of mulberry plants have been developed and are being cultivated. These varieties are called as \[{{M}_{2}}\] and \[{{M}_{5}}\]varieties. They gave 100% increased yield of mulberry leaves upon which the silk worm feeds.

Different varieties of silk worm, Bombyx mori and Autherea have been developed which can be cultivated in various states. Existing races of silk worm are being improved Bivoltine species are being developed. Low production and higher yield have been achieved as a result of these efforts. India is producing 4200 metric tons of silk per annum (1980). This figure is even higher at present. India is exporting some 25% to 30% of its total silk production in the form of silk garments and fabrics. Karnataka is the biggest silk producing state followed by Jammu & Kashmir and Tamil Nadu, Madhya Pradesh is also emerging on the scene of silk production. India is producing China silk, Tasar silk or Cosa silk, Muga silk and Eri silk today.

Systemic position

Phylum -              Arthropoda

Class      -              Insecta

Order    -              Lepidoptera

Family   -              Bombicidae and satarnidae

Family – Bombicidae

(1) Bombyx mori : It is known as China silk worm or mulberry silk worm. It is native of China. It has been fully domesticated for the production of silk. It produced quality of silk which is white silk or yellow silk.

(2) Other species of Bombyx are B. texior, B. fortunatax and B. meridionles. They are well Known in our country.

Family - Saturnidae : Antheraea paphio - It belong to the family saturnidae. It is widely distributed in india in the states of Karnataka, Tamilnadu, Madhya Pradesh, Uttar Pradesh, Bihar and West bengal. It feed on and fig plants. Its favourite host plant is Arjun (Terminalia arjuna), sol (shorea robusta). It has been recently domesticated for sericulture. It produced Tassar silk (kosa silk.)

Habit and habitat : The silk worm distributed in temperate regions are diapause type i.e. they remain inactive for some time in winter. The silk worms inhabiting some tropical regions.

Adult Moth : The moth measures about 25 mm in length and wing span measures about 40-50 mm in width. Female moths are larger than male moths. In general univoltine races are of larger size that multivoltine.

It has whitish colour with gray marks on wings in some races. The body is divisible into head, thorax and abdomen. Head contains a pair of eyes and a pair of pectinated antennae specially larger in males. Thorax contains three pairs of legs and two pairs of wings covered with scales. Female moths are without mouth. The abdomen is plump. Digestive system is poorly developed. The excretory system consists of three pairs of malpighian tubules present at the end of mid gut. The reproductive system is very well developed in females and males.

Life History

(1) Copulation : The copulation lasts for about three hours. During copulation the male sits over the female and holds her with the help of chitinous hooks. Both the moths acquire back to back' position. The female has a scent gland at the terminal end of the abdomen, which secretes volatile secretion called pheromones to attract the male.

(2) Egg : Copulation is immediately followed by egg laying. The eggs are small, oval and creamy white in colour. They become darker as they become older. Each moth lays about 300 to 500 eggs. The eggs are glued to the under-surface of the leaves of the host plant.

(3) Larva : After hatching a larva comes out of egg. It is called as caterpillar larva. It is 1.2 mm to 3 mm in length depending upon the race. It has grey or creamy-white colour.

The body of larva is divided into head, thorax and abdomen. The head consists of three fused segments. Mouth parts are biting and chewing type or strongly mandibulate. A pair of antennae and six pairs of are also present on head. Mandibulate mouth parts are used to cut and chew the leaves. The thorax consists of three segments. Each segment contains a pair of legs with recurved hooks. They are used for locomotion and manipulation of food during feeding. The abdomen consists of ten segments. The last and tenth segment is poorly developed. Five pairs of pseudo legs are present on 3rd, 4th, 5th , 6th  and 9th  abdominal segments. These are used for locomotion.

  • Silk gland : Among other visceral organs larva contains well-developed paired glands called silk glands. When fully developed, these glands becomes five time larger than the length of the larva and there weight becomes 2/5th of the total body weight. Its secretion probably lubricates the silk. The silk is secreted in liquid form, which solidifies on coming in contact with air.

The larva is voracious eater. It feeds on mulberry leaves. It may ingest about 30,000 times more than its body weight during its complete larval period and increases about 10,000 times more than the body weight of its body from the time of hatching. As the larva grows, it sheds it cuticle. This is called as moulting. The form of larva between two successive moults is called as instar. The larva has five instars:

Ist instar  - from hatching to Ist moult

IInd instar - between Ist moult and IInd moult

IIIrd instar - between IInd moult and IIIrd moult

IVth instar - between IIIrd moult and fifth moult

Vth instar - between fifth moult and pupation

A fully-grown larva of Vth instar attains the length of 7.5 cm. It stops feeding and starts spinning the cocoon. It secretes silk thread from its spinneret and forms covering in which it encloses itself completely. It takes about 3-4 days to spin the cocoon.

(4) Pupa : The cocoon consists of silk thread. The enclosed immobile larva in the cocoon is called as Pupa. The pupal stage is non- feeding and non-mobile. It remain & inactive.

(5) Cocoon : The cocoon is white or yellow in colour. It is made up of about 1000-1200 meters long silk thread. The thread is wound around the cocoon is concentric circles. The weight of one cocoon is about 1.8 to 2.2 gms. The pupal period lasts for about 10 to 12 days. Alkaline fluid which makes the threads of cocoon to be soft. Soft threads are cut open by the imago. A young moth comes out of cocoon.

 

 

(6) Fertilization : After the moths emerge out from cocoons one female from one lot is kept with the male from another lot. They form pair and copulate. After copulation is over separated and kept with female of another lot. Thus one male can be used to fertilize at the most two females of different lots.

(7) Egg laying : After fertilization the female starts laying eggs. Egg laying is completed in about 24 hours. The laid eggs are called seeds. The eggs are transferred in sterilized and tray stored at 4°C.

Factors influencing the life cycle : The life cycle is influenced by the external environmental factors, such as, temperature, humidity and light. These factors control the growth of the larvae and also the quality of silk produced. The growth and moulting is controlled by hormones called juvenile hormone and ecdysone.

Composition of silk : The silk is a secretory product of silk glands of the larva. Silk is composed of proteins. It consists of an inner part made up of fibroin protein \[({{C}_{30}}{{H}_{46}}{{N}_{10}}{{O}_{12}})\]and is covered with an outer envelope made up of sericin protein \[({{C}_{30}}{{H}_{40}}{{N}_{10}}{{O}_{12}}).\] The silk thread contains \[75-80%\] fibroin and \[20-25%\]of sericin,

Sericulture industry : Sericulture industry involves  three steps,

(1) Mulberry cultivation : Mulberry is the only food of silkworms. Mulberry plants come up in any soil and in any climate. It is propagated by cuttings. The land is ploughed well 6 or 7 times in April-May and manured at the rate of 2 to 25 tons per hectare. Small pits are scooped out 2 or 3 cuttings are lanted in pit. Each cutting should be 20 to 23 cm in length with nodes. When the plants grow too high they are cut back and this is known as pruning.

Pruning : Pruning will help in the production of a new flush of leaves. The plants can yield for 12 years. Every year 6 to 8 crops of leaves can obtained and the average yield per hectare is 25 to 30 metric tons of green leaves.

(2) Silk worm rearing - Silk worm rearing needs the following:

(i) Rearing house

(ii) Rearing trays and stands

(iii) Chandrikes as support to build the cocoon.

The hybrid eggs are obtained from the sericulture department. The larvae are hatched from the eggs. The newly hatched larvae are brushed into rearing trays and tender, chopped are provided to them. At the end of the final instar, fully grown mature larvae are transferred from the rearing trays to chandrikes and allowed to build cocoons. Cocoons are then collected and marketed.

Grainage Management : This is done to provide good quality of seed to rearers and also to maintain the original quality. With this air grainage management is done by taking of caterpillar stage. They are protected from diseases and are provided good nutrition. An initial selection is made by observing pupal mortality rate. If the mortality rate is high, then such cocoons are rejected and are not kept for seed production. If the mortality rate is sufficiently low, their only such cocoons are selected and kept for seed production. The selected cocoons are kept for mass emergence. Before doing so the cocoons are examined and sexed. Males are kept separately and females are kept in separate lots.

(3) Hatching : The process by which larvae come out of the egg is known as hatching. After hatching larvae start eating mulberry leaves. The success of sericulture depends on the supply of good quality of mulberry leaves; therefore the hatching must coincide with good mulberry season. Now a days controlled hatching is done by placing the eggs in low temperature. The eggs are turned and moved with the help of a feather. Now -a-days the eggs are kept in mulberry leaves in sterilised trays. If hatching is to be delayed or controlled, the eggs are kept in separate trays and refrigerated for a suitable time.

The caterpillars which hatch out are kept in separate groups according to their age.

(4) Supply of seeds to rearers : Under this step they are supplied with seeds. The seeds are of two qualities, i.e., eggs and 2nd instar larvae. Beginner rearers are supplied with 2nd instar larvae, which experienced rearers can purchase egg. This is important operation. For this purpose government has established many silk worm seed centres from where the rearers get their seeds at fair price.

(5) Rearing of Caterpillars : The caterpillars are reared at room temperature in shady places at about 60 to 70% humidity. The mulberry leaves supplied to Ist and 2nd instar larvae are well chopped, fresh and kept in wet clothes so as to keep them fresh. The caterpillars eat voraciously and grow in size and moult. The form of larvae between two successive moults is known as instars. Larvae have five instars. The last or 5th instar larvae stop feeding and undergo pupation.

(i) Spinning of Cocoons : Full grown 5th instar larvae secrete a pasty material from its silk gland. It moves its head to and fro, secreting a silk thread.

A good quality of cocoon is judged by the quantity of raw silk, filament length, strength and splitting power. The cocoons are marketed and sold.

(ii) Post Cocoon Processing : It included following stages:

(a) Stifling : The process of killing the cocoons is termed as stifling. Eight to ten day-old cocoons are selected and dipped in hot water to kill the pupae in the cocoons.

(b) Reeling : The silk threads from the killed cocoons are removed and wound round a large wheel and then transferred to spools. This operation is called as reeling and the silk is called as reeled silk.

(c) Spinning : Damaged cocoons or the damaged outer layer of silk is separated and spun into threads. This is known as spun silk.

The raw silk is boiled, stretched, purified and washed again and again to shining lustre. Reeled silk or spun silk is marketed and sold.

Problems of Sericulture : The sericulture industry is facing a number of problems.

(1) Need for Research : There is a great need to better methods of rearing the silk worms. This is necessary to improve the yield of raw silk and reduce the cost of production.

(2) In order to improve the quality and yield of raw silk improved varieties of silk worm are developed by hybridization and breeding. There is a need for the improvement of genetic quality of the silk worm.

For research and training in sericulture the Government has opened Research and Service Station in many states. A Central Silk Board has been established at Bangalore the ministry of commerce.

Disease of silkworm

(1) Pebrine : It is the most important disease of silkworms. It is caused by a sporozoan called Nosema bombycis. The full grown caterpillar is attacked.

(2) Muscardine : It is a fungal disease caused by Beauveria bassiana and transmitted by spores carried by winds. All stages of caterpillar are attacked.

(3) Flacherie : It is a bacterial disease caused by Bacillus bombysepticus. Digestion in the affected caterpillar gets disturbed Regular feeding of the larvae and maintaining hygenic conditions will prevent the disease.

(4) Grasserie : The causative agent of this disease is the nuclear polyheadrosis virus. The affected larvae become swollen and like a bag of granules, the body fluid becomes thick and cloudy and the larvae die.

Economic Potentialities of Cultivating Silk in Madhya Pradesh : Madhya Pradesh is the largest state with respect to land area and has rich subtropical vegetation. Thus Madhya Pradesh holds vast economic potentialities of cultivating silk Sericulture is an important rural cottage industry. The tribal and other rural population in south east and east M.P. is favourably disposed for the cultivation of silk. Once M.P. was not a significant state in the list of silk producing states of India but due to the efforts of Madhya Pradesh Government in the direction of promoting sericulture today it, is the second largest state after Karnataka in the field of production of raw silk.

Efforts made by Government of M.P. to Promote Sericulture in state : A directorate of silk has been organised under the Panchayat and Rural Development Department to make concentrated efforts. These activities have been divided in two categories :

(1) Kosa silk Area : It extends in the eastern and south eastern parts of the state. This area is predominated by tribal   population and is spread in the districts of Balaghat and Mandla.

(2) Mulberry silk Area : It is spread in the western and middle parts of the state including the districts of Indore, Dhar, Dewas, Khandwa, Ujjain, Shajapur, Raigarh, Mandsaur, Guna and Sehore. For the promotion of the production of Kosa silk (now Mulberry silk) following efforts are being made.

(i) Kosa Seed Centre : Twelve Kosa seed centres have been established to provide scientific and technical information to the Kosa silk worm rearers. These centres also provide disinfected improved kosa seeds and caterpillars to the rearers.

(ii) Kosa Guidance and Training Centre : Madhya Pradesh Government has established 67 centres which meet the basic needs of supplying disinfected improved seeds of Kosa silk and impart training and guidance to the rearers.

(iii) Nursery : To meet the needs of the host plant and supply of leaves to the rearers the government has established nurseries of Terminalia tomentosa and Terminalia arjuna. Plantation of host plants has been undertaken in 296 hectares of land and 1285 hectares of land is proposed to be covered under this scheme.

(iv) The construction of two grainage, one cold storage, one cocoon market and one reeling factory is being undertaken.

(v) Kosa Regional Research centre has been established to help the rearers to increase the yield and improve the quality of silk.

(3) Mulberry silk Plans : To promote the mulberry silk production in M.P. certain efforts have been made in the direction by the Madhya Pradesh Government. These are

(i) Establishment of Nursery : To increase the production of host plant Mulberry silk worm, the Morus indica, nurseries have been established.

(ii) Mulberry silk seed centres have been established.

(iii) Integrated rural development projects have prepared for the production of Mulberry silk.

(iv) Establishment of regional research centre and reeling factory.

(v) Demonstration and publicity plans.

Madhya Pradesh Government has allocated 476.22 lac of rupees for the development plans of silk for the year \[1985-86\] a target of 80,000 kg. of Kosa silk and 8356 kg. of Mulberry silk.

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