Synopsis

Introduction

History

What is silkworm

Types of silkworms

External features of silkworm

Host plant

Life cycle of silkworm

How silkworm produce silk?

Sericulture

The technology of sericulture and silk production

Diseses of silkworm

Economic importance of sericulture

Uses of sericulture

Introduction

Sericulture is a silk producing agro-industry and India is the second largest silk producing country in the word next to China.

the word ‘sericulture’ is derived from the Greek ‘sericos’ meaning ‘silk’ and the English ‘culture’ meaning ‘rearing’. Sericulture is a branch of applied zoology which deals with the rearing of silkworms for commercial production of silk. Sericulture refferes to the conscious mass- scale rearing of procucing organism in order to obtain silk from them. Mulberry sericulture invovels the cultivation of mulberry to produce leaf, rearing of silk worm to convert leaf to cacoon, reeling of the cocoon to obtain silk yarn and weaving to convert yarn to fabrics.

History-

According to legend, silk was discovered in China, at around2700 B.C. The emperor’s mulberry trees were being damaged by silkworms. His wife was picking a cocoon off the tree, but dropped it into hot water by mistake. Afterward she discovered that the cocoon could be unwound to produce a lustrous fabric. A fabric we now know as silk. At the time the secret of silk was closely guarded and reserved only to China’s emperors and other important people. As time passed the secret to the creation of silk spread to India and Europe. Now the whole world knows about silk. This fiber has remained in high production and remains on top of many new fibers. A strand of silk is even stronger than a strand of steel of the same size. For these reasons silk is still widely used by the world today. Although silkworms are raised largely by huge companies for silk, they are also raised for reptile food and sometimes as pets. Raising silkworms is easily done and the caterpillars have many Uses. Sericulture or silk farming, is the rearing of silkworms for the production of

raw silk. For thousands of years, the secrets of silkworm rearing (called “sericulture”) were closely guarded in China. The penalty for releasing any information to the outside world—from what created the silk, to how to culture the silkworms, and how to process the raw silk—was death. However, eventually silkworm domestication spread from China; Chinese immigrants took the silkworms and their secrets with them in the 200s B.C. to Korea. From Korea, the knowledge of silk production made its way to Japan around 200 A.D. Around 550 A.D., silkworms arrived in the Byzantine Empire and were presented to Emperor Justinian. Although China had been trading silk since 200 B.C. along the Silk Road, (the Silk Road was a trading route) no secrets had left Asia until then. While it’s unclear whether the silkworms were smuggled by monks or merchants, either way, the silk industry began to get a foot hold outside of Asia. In Byzantium, the silk industry developed slowly under tight government regulation. It was not until between the 700s and 1000s A.D. that silkworms and culturing information made their way to Europe through Spain, Italy, and France. Silk culturing became so ingrained with European life that silkworms arrived in North America in the 1600s with colonists. Because silkworms were domesticated and easy to manage early on in scientific history, early scientific discoveries were made using these critters. In 1835, Italian entomologist Agostino Bassi identified a microorganism (the soil-dwelling fungus Beauveria bassiana) as causing a fatal disease in silkworms. Microorganisms had not been previously identified as being responsible for diseases.

What s a silkworm?

Systematic position of silkworm-

Phylum - Arthropoda

Class - Insecta

Subclass- Pretygota

Division - Endopterygota

Order - Lepidiptera

Type - Bombyx mori

The silkworm is the larva or caterpillar of the silk moth, Latin hatching from an egg, the worms take one month to grow large enough to spin the silk. They spend three weeks in the cocoon, then emerge as a moth to mate and lay eggs. The eggs hatch into worms in a few weeks, and then the cycle continues. Silkworms go through four stages of development, as do most insects: egg, larva, pupa and adult. The adult (imago) stage is the silkworm moth. The larva is the silkworm caterpillar. Since the silkworm grows so much, it must shed its skin four times while it is growing. These stages-within a-stage are called instars. Bombyx mori. Bombyx mori means "silkworm of the mulberry tree". It is the producer of silk. A silkworm's eats leaves from the white mulberry tree (Morus alba). The silkworm caterpillars spin a silk cocoon and change into moths while inside. Most of the commercial silk produced in the world comes from this variety and often silk generally refers to mulberry silk. Mulberry silk comes from the silkworm, Bombyx mori L. which solely feeds on the leaves of mulberry plant. These silkworms are completely domesticated and reared indoors.

Types of silkworm-

Tasar:Tasar (Tussah) is copperish color, coarse silk mainly used for furnishings and interiors. It is less lustrous than mulberry silk, but has its own feel and appeal. Tasar silk is generated by the silkworm, Antheraea mylitta which mainly thrive on the food plants Asan and Arjun. The rearings are conducted in nature on the trees.

Oak Tasar:It is a finer variety of tasar generated by the silkworm, Antheraea proyeli J. in India which feed on natural food plants of oak, found in abundance in the sub-Himalayan belt. China is the major producer of oak tasar in the world and this comes from another silkworm which is known as Antheraea pernyi.

Eri:Also known as Endi or Errandi, Eri is a multivoltine silk spun from open-ended cocoons, unlike other varieties of silk. Eri silk is the product of the domesticated silkworm, Philosamia ricini that feeds mainly on castor leaves.

Muga: This golden yellow color silk is prerogative of India and the pride of Assam state. It is obtained from semi-domesticated multivoltine silkworm, Antheraea assamensis. These silkworms feed on the aromatic leaves of Som and Soalu plants and are reared on trees similar to that of tasar.

OTHER SILKWORM

Making silk is common with moths. Many wild moths create a silken cocoons. Of them is the Chinese Oak Moth, Robin Moth, and the Luna Moth. Most of these moths and their caterpillars are much prettier than the Bombyx mori. However, Bombyx Mori is used to make silk because of the silk’s quality. Most silk moths do not create workable silk. The Chinese Oak Moth creates a coarser, browner silk than the Bombyx Mori. This silk is called Tussah and is mostly used as filling. The oak moth caterpillars are hairy and green, and the cocoon is hard and brownish. The caterpillars eat oak leaves. The moth that emerges is a beautiful peachy color.

External features-

The adult moth is about 25 mm long with a wing span of 40-50 mm. it is robust and creamy white in colour. The body is divided into three portions, namely head, thorax and abdomen. The head bears a pair of compound eyes, a pair of branched or plumed antennae and mouthparts. The thorax bears three pairs of legs and two pairs of wings. The cream coloured wings are about 25mm long and marked by several faint or brown lines. The entire body is covered by minute scales. The body of female moth is much distended due to great number of eggs it contains. It is unable to fly due the heavy body and feeble wings. The moth does not feed during its short span of life of 4 or 5 days only.

Host plant-

The White Mulberry Tree Just as monarch caterpillars depend upon milkweed, silkworms eat mulberry tree leaves specifically the white mulberry (Morus alba). The white mulberry is a large, deciduous tree, that has deep purple fruit. (Deciduous means that the tree loses it's leaves in the fall.) Other varieties of the mulberry can have black, red, or white edible berries, or it can be fruitless. Cultivation of white mulberry for silkworms began over four thousand years ago in China. The white mulberry is now widely planted. It has been grown widely from India, west through Afghanistan and Iran to southern Europe for over thousand years for leaves to feed silkworms. Silkworms are attracted to mulberries by a chemical fragrance the leave release specifically called cis- jasmone. The silkworms’ relationship with the mulberry tree is so close that the domestic silk worm is named after the mulberry tree.

Life cycle of silkworm –

the silk worm is dioecious, i.e. the sexes are separate fertilization is internal, preceded by copulation. Development includes a complicated metamorphosis.

Eggs- soon after fertilization, each female lay about 300-500 eggs in the clusters upon the leaves of the mulberry tree. The female covers the eggs by gelatinous secretion. The small, smooth and spherical eggs are first yellowish white and become darker later on. After laying, the female does not take a food and dies within 4-5 days.

Caterpillar larva- the silkworm which hatches from the eggs is known as the caterpillar. It is a tiny creature, about 6 mm long, and moves about in characteristic looping manner. It has a rough and wrinkled, whitish or greyish body, which is made up of 12 segments. Head bears mandibulated mouthparts. The thorax with distinct 3 segments, has 3 pairs of jointed true legs. The 10 segmented abdomen is provided with 5 pairs of unjointed, stumpy pseudolegs, a short dorsal anal horn on the 8th segment and a series of respiratory spiracles on either lateral side. The caterpillar at once starts to

feed voraciously upon mulberry leaves and grow quickly. The larva undergoes moulting process four times. The maturity with full size is reached within 45 days since the time of hatching. Silk worm is now 8 cm long. A pair of salivary glands now develop in the lateral sides. Silk thread is made of 5 filaments stuck together by a gummy substance or sericin which is selected by two other glands.

Pupa or chrysalis – the caterpillar now stop feeding and return to corner among the leaves. It now begin to secret the sticky fluid of it salivary gland through a narrow pore, called spinneret, situated on the hypopharynx. The sticky substance turn in to a fine long and solid thread of silk into the air. The thread becomes wrapped around the body of caterpillar forming a pupal case a covering known as cacoon. This process goes on for about 3-4 days at the end of which the silk worm is enclosed within a thick, oval, white or yellowish silken caccon. A single caterpillar is said to produce nearly 1000-1500 meters of silk thread.

Imago - active metamorphic changes now take place during pupation. The unsegmented abdominal prolegs disappear, while the thorax develop two pairs of wing. The pupa finally metamorphoses into a baby insect or imago, which secret a alkaline fluid to moisten one end of cacoon and escape by forcing its way out of the softened silk. Soon after emergence the moth mate, lay egg anf die.

How silk worm produce silk?-

The silkworm (Bombyx mori) was native throughout Asia, and domesticated in China over 5,000 years ago to make silk. Legend has it that around 2700 B.C., empress Xi Ling-Shi observed caterpillars eating the local mulberry trees, when one of the cocoons fell into her hot tea. The cocoon unraveled in the boiling water, turning into a long strand of silk. While there is no way of knowing whether this legend is historically accurate, archaeological excavations have found 5,000-year-old silk products in China, revealing that the domestication of the silkworm had already taken place. It would have been hard to predict that these little caterpillars would create a thriving economic export; silk production is now a multi-billion dollar industry, with around 150,000 tons of silk created every year.Silkworms today are biological silk-producing machines that are the product of thousands of years of careful breeding. Because they have such short life spans, one silkworm moth can produce hundreds of caterpillars. Silkworms were quickly and easily bred for certain desirable traits over many generations. At around 77 degrees

Fahrenheit, a fertile silkworm egg will hatch after only seven to ten days. The newborn is very tiny (around 1/8th of an inch long) and covered with black hairs, but as the caterpillar matures it becomes white,hairless, and quite soft. After three to four weeks of constant eating and growing, a silkworm can reach a plump three inches in length, increasing its mass an amazing 10,000 times since hatching. When the silkworm starts to spin a yellow or white cocoon, which takes around four days to complete. The reason some cocoons are yellow and some are white is because of genetics. Just like people, some people have blue eyes and others have brown eyes.Almost all commercial varieties of silkworms make white silk.

There are also silkworm varieties that make yellow, orange and pale-green silk. When you cross-breed a "whitesilk" silkworm moth with a "yellow-silk" silkworm moth, you get some yellow offspring and some white offspring. When you have a mom with blue eyes and a dad with brown eyes, some of their kids will have brown eyes and others will be blue-eyed. Same idea. With people, brown eyes are dominant. With silkworms, the colored silk is dominant over white. Wild silkworms all make yellow silk, to blend in with dead leaves. Over the centuries, silkworm farmers selectively bred for whiter and whiter silk until they achieved the pure white we see today. They like the pure white because it can be dyed any color without having to bleach it first. Nowadays, with natural and organic products gaining in popularity, people are selectively breeding for colored silks. You can propagate eggs for white, yellow, orange and green silk. Cotton farmers have recently begun to breed for colored cottons and have a wide variety of naturally-colored cottons, including yellow, pink, pale-green and orange. The silkworm moth has been bred to have a large body and small wings, with a wingspan of one-and-a-half to two inches, the female's wings are even smaller. Because of this the domesticated silkworm moth cannot fly. The female is larger than the male and has a large abdomen for carrying many eggs. After the female moth mates and lays about 300 eggs, it dies, but the cycle starts anew with the eggs. Silkworm caterpillars take about a month to get big enough to spin a cocoon. The cocoon-spinning process takes about three days. When the silkworm ate great quantities of mulberry leaves, they were digested and nutrients were

sent into the bloodstream. The silk glands absorbed these nutrients. The silk is actually hardened silkworm saliva. The larva has a small spinneret on its lip of its mouth (notout of the rear end like a spider) , through which the silk emerges. To create the silk, silkworms secrete a fluid, from its salivary glands, that is pushed through special openings, called spinnerets, on their mouth parts. The fluid hardens and turns into a thread of silk, which the silkworm uses to make the cocoon around its body. The silkworm moves its head in figure 8 patterns as it spins the cocoon. The entire cocoon is made by a single thread, which can be around 3,000 feet long!

Extraction of silk:1. Extraction of silk from cocoon includes stifling, reeling and degumming.

2. Well grown cocoons are collected and soaked in boiling water to kill pupa is called as stiflfing.

3. Stifling is also essential for loosening silk threads in cocoon.

4. Loosen silk thread rapped around a wheel to obtain a long continuous thread called as reeling.

5. Such reeled silk thread is boiled to remove extra gum called as degumming.

SERICULTURE

MAKIING OF SILK

Raw silk thread, called a “filament,” is drawn from the cocoons of several moth species. The caterpillars that spin the cocoons are commonly called “silkworms.”

Silk production involves growing mulberry trees to provide food for the silkworms, which eat more than fifty thousand times their weight in mulberry leaves. It also involves caring for the silkworm as an egg, a caterpillar, and as a chrysalis within a cocoon. The chrysalis is the final stage before the silkworm emerges as an adult moth. The female moth lays hundreds of eggs, each about the size of a pinhead, before dying almost immediately after. The eggs are stored through the winter and allowed to hatch only the following spring. The Silkworm (Bombyx mori) Is Not a “Worm” At All.

This Figure Shows the Caterpillar of a Moth Whose Cocoon is Used to Make Silk About four to six weeks after hatching, the caterpillars reach maximum size and begin to spin their cocoons. This takes about four days. Glands on the caterpillar’s head secrete a liquid that becomes the silk filament. Each cocoon is made of a single filament, two to three thousand feet long. In order to kill the chrysalises, the finished cocoons are either steamed, put in jars layered with salt, or boiled. The caterpillars have to be prevented from becoming full-grown moths in order to preserve the cocoon and its thread. The only moths allowed to live are those selected as breeding stock for future generations of silkworms.Each cocoon is made of a single filament two or three thousand feet long. This is called “floss,” which is twisted to make silk thread. Although the Chinese used other raw materials such as hemp to make cloth, silk was the most useful and valued fabric for many centuries. It was only with the spread of cotton production in the fourteenth and fifteenth centuries that silk was eclipsed as a fabric for daily use. In his Spring Silkworms, the twentieth century writer Mao Dun (1896-1981) refers to the time when silkworms incubate as the “sacred season.” His characters call the cocoons “little

darlings.” This shows not only how dependent silk farmers were on the life cycle of the silkworm, but also gives a sense of how difficult and complicated it was to raise them successfully.

The technology of sericulture and silk production

The technology of sericulture and silk production is well-known. In brief, various aspects involved in it are as follows:

Mulberry Cultivation: Silkworms feed on mulberry leaves. Hence the rearing of silkworms involves cultivation of mulberry trees, which provide a regular supply of leaves. Worms are introduced through DFLs (Disease Free Layings, i.e.eggs) procured from a quality centre (called grainage). In India, the bulk of mulberry cultivation is done by small farmers (< 4 acres land), usually in clusters of 300-400.

Rearing: The silkworms are actually larvae of the silkmoth. They are reared in specially made trays in rooms with controlled temperature and humidity and regularly fed mulberry leaves. At a certain stage they convert themselves into cocoons. These cocoons are made from a single filament of material secreted by the pupa and wrapped around itself for protection. These filaments upon hardening constitute silk. On an average, 1 acre of plantation would yield 240 kg of cocoons in an year, starting from 100 DFLs. Depending upon whether it is dryland or irrigated mulberry, farmers can harvest the cocoons 4 to 8 times in an year.

Reeling: The removal of silk yarn from the cocoons iscalled reeling. This is done by first cooking them in water to remove the gum, which holds it together, and then unwinding the filaments (reeling). Usually 8-10 cocoons are reeled together. There are three methods for reeling: the charkha, the slightly more advanced cottage basin and the costly automatic machines.

Twisting: Prior to weaving, the raw silk is boiled in water to remove remaining gum, dyed and bleached, and then woven into the garment – usually on handloom. In some cases the woven cloth may be dyed and bleached.

Disease of silkworm-

Silkworm diseases are the major constraint in sustainable cocoon production. The common diseases in silkworm are Grasserie, Flacherie, Muscardine and Pebrine, caused by highly infectious pathogens. The development of diseases is also influenced by nutritional and

environmental factors.

1. Pebrine disease-

Pebrine is a chronic disease in silkworm. The disease i s known to occur throughout the year and is not restricted to any season .The microsporidian, Nosema bombycis and strains of Nosema sp. Are the causative agents. Practice disinfection at silkworm seed production center, silkworm rearing house, its surroundings and appliances.

Rear silkworm hatched from eggs prepared from pebrine free moths ascertained by microscopic examination of the mother moth. Practice hygiene measures during silkworm rearing. Ensure measures for proper disposal of diseased silkworm, faecal matter, cocoons, eggs, etc. Apply bed disinfectant, Ankush/Vijetha as per recommended schedule and quantity. Control alternate insect hosts of Nosema bombycisin and around mulberry garden.

Symptoms

The eggs laid by moth are fewer and do not firmly attach to the egg sheet. The diseased larvae have poor appetite, retarded growth, undersized and flaccid. The larvae are comparatively paler, translucent and delays to moult. The silk gland will have white pustules on its surface. The dead larvae remain rubbery for sometime and then turn black. The diseased pupa may develop black markings on the surface. The moth appears malformed. The wings are stunted and crippled.

Management

Practice disinfection at silkworm seed production center, silkworm rearing house, its surroundings and appliances. Rear silkworm hatched from eggs prepared from pebrine free moths ascertained by microscopic examination of the mother moth .Practice hygiene measures during silkworm rearing. Ensure measures for proper disposal of diseased silkworm, faecal matter, cocoons, eggs, etc. Apply bed disinfectant, Ankush/Vijetha as per recommended schedule and quantity. Control alternate insect hosts of Nosema bombycis in and around mulberry garden.

2.Grasserie disease

Grasserie disease is commonly known as nuclear polyhedrosis, milky disease and hanging disease. The disease is caused by the Bombyx mori Nuclear Polyhedrosis Virus (BmNPV). The disease prevails all through the year but is more common in summer and rainy seasons.

Symptoms

At the early stage of infection, the silkworm appear normal , but during the later stage of infection, the larvae will have swollen inter segmental region. The integument will be fragile and breaks easily oozing turbid milky fluid. The larvae do not settle for moult and their integument become shining. Practice disinfection and hygiene in silkworm rearing. A spray of 0.3% slaked lime solution in addition to usual disinfection. Apply

bed disinfectants Ankush/Vijetha as per recommended schedule and quantity. Avoid low (<20ºC) and high (>28ºC) temperature and humidity (below 70%) as well as drastic changes in temperature and humidity during the rearing. Feed nutritious mulberry and provide required spacing and ventilation. Feed Amruth as a curative agent as per schedule and quantity.

Management-Practice disinfection and hygiene in silkworm rearing.A spray of 0.3% slaked lime solution in addition to usual disinfection. Apply bed disinfectants Ankush/Vijetha as per recommended schedule and quantity. Avoid low (<20ºC) and high (>28ºC) temperature and humidity (below 70%) as well as drastic changes in temperature and humidity during the rearing. Feed nutritious mulberry and provide required spacing and ventilation. Feed Amruth as a curative agent as per schedule and quantity.

Amruth

An Eco and user-friendly botanical based formulation for controlling Grasserie and Flacherie diseases of silkworm.The first ever curative formulation for silkworm diseases.Mix Amruth powder in water @ 20g/liter. Spray/ sprinkle 70 ml of Amruth solution per kg of mulberry leaf/shoot.

3.FLACHERIE

Flacheie is a flaccid disease common in silkworm .The disease prevails all through the year,but severe during winte and rainy seasons.The disease is caused by Bombyx mori infectious flacherie virus (Infectious flacherie) and Bombyx mori densonucleosis virus (Densonucleosis) and inassociation with bacteria or bacteria alone. The diseased silkworms, their feces, gut juice, body fluid, and alternate hosts are the sources of infection.Symptoms are atypical at the early stage of infection. Larvae appear lethargic and lose appetite.

Symptoms

Viral Flacherie results in retarded growth of larvae. They become dull, soft and flaccid. The larvae vomits gut juice and develop dysentery. Bacterial flacherie results in stunted growth of larvae and develops flaccidity. The larvae on death putrefy, develop different colour and emit foul smell.

Management- Practice disinfection and hygiene in silkworm rearing house, surroundings and appliances. Spray 0.3% slaked lime solution in addition to usual disinfection. Feed good quality mulberry leaf, provide requisite spacing and ventilation. Avoid overcrowded rearing and accumulation of silkworm waste in the rearing bed. Maintain optimum temperature and humidity. Apply bed disinfectant Ankush/Vijetha as per recommended schedule and quantity. Feed Amruth as a curative measure as per schedule and quantity.

3.MUSCARDINE

White muscardine is the common fungal disease and is caused by Beauveria bassiana. The disease prevails during winter and rainy season in all sericultural areas.The disease is also common in many agricultural pests. The infectious conidia penetrate through the integument and establish infection in silkworm. Practice disinfection of silkworm rearing house, surroundings and appliances. Practice hygiene measures during silkwormrearing.Ensure measures for proper disposal of diseased silkworm. Regulate rearing bed humidity by dusting slaked lime at the beginning of every moult and in between, if necessary to keep the rearing bed dry. Provide good ventilation.Apply bed disinfectant, Ankush/Vijetha and Vijeha Supplement as per recommended schedule and quantity. Control alternate insect hosts of Beauveria bassianain and around mulberry garden.

Symptom-The larvae loose appetite, become inactive and flaccid on death. Vomiting and diarrhea may also be observed. The larval body becomes less

elastic and oil stain like or black marks without clear border may be seen on the body surface. Dead larvae gradually become harder and finally mummifies. The fungus overgrow the larvae, develops fruiting body and produce conidia on the surface giving whi t e col our t o t he mummi f i ed diseased silkworm.

Management-

Practice disinfection of silkworm rearing house, surroundings and appliances. Practice hygiene measures during silkworm rearing. Ensure measures for proper disposal of diseased silkworm. Regulate rearing bed humidity by dusting slaked lime at the beginning of every moult and in between, if necessary to keep the rearing bed dry. Provide good ventilation. Apply bed disinfectant, Ankush/Vijetha and Vi j et ha Suppli- ement as per recommended schedule and quantity. Control alternate insect hosts of Beauveria bassiana in and around mulberry garden.

Pests- following parasites and predators cause destruction of the silkworm.

1. Uzi flies- Tricholyga bombycis (Diptera)young maggots bore body of silkworm and live in and eat fat body for about a week, causing the death.

2. Dermestid beetle- Dermestes cadeverinus larvae and adult feed on cacoon.

Other predators include ants, lizards, rats, squirrels and birds like sparrows are feed on silkworm.

Economic importance of sericulture

Importance of Sericulture:

1. It is an agro based side business require less investment and return it to the farmer with more benefits.

2. Mulberry silk is used in the preparation of valuable cloths like sarees shawls.

3. Tassar silk is used for making mens wear like shirts, jackets, trousers, etc.

4. Muga silk is specially used in the embroidery works.

5. Silk is a bad conductor of heat and electricity so used as insulators, for telephone wires.

6. By exporting silk and silk products from India our national economy goes on increasing.Knowledge of diseases of silkworm and their prevention

Uses of silk-

The raw silk thread woven into cloth has several uses. Sarees, kurtas, jackets, blouse, showls, curtains and other garments are prepared from it. It is knitted into goods such as gloves, stockings, socks, vests, etc.

Articles manufactured include tyres of racing cars, insulation coils for telephones and wireless receivers, sieves for four mills, fishing lines, parachute cords, parachute, etc.

Uses of silkworm-

Apart from yielding the much valued silk, the silkworm are useful in a few other ways. The chrysalids obtained from cocoons are dries and since they are rich in protein, are used as fertilizers. The fatty mater is used in soap manufacture.