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Sericulture

Keeping and rearing silkworms to obtain raw silk from a business point of view is known as sericulture.

• Firstly in 2697 B.C in China, the queen of the country K Wang Ti invented silk.
• In India, the first experiment for the study and rearing of silkworms was done by Lefroy in 1905 at the Pusa Institute of Delhi.
• In India, in last 15-20 years there has been great improvement in the quality and type of silk. Indian silk is famous for its quality, lustrous shining and traditional color combinations the whole world.
• Main silk-producing states of India are Assam, West Bengal, Tamilnadu, Punjab, Kashmir, and Karnataka.
• India is the second-largest silk producer globally, after China. The two countries account for over 60% of global production annually.
• India produces four silk varieties: Mulberry (91.7%), Tasar (1.4%), Eri (6.4%), and Muga (.5%). Muga silk is exclusively produced in Assam.

Species of Silkworms

Lifecycle of Silkworms

• The life cycle of the mulberry silk moth consists of four stages: egg, larva, pupa, and adult moth.
• The adult silk worms are approximately 4-5 cm long and are of a dirty white color.
• Fertilization is internal.
• The egg stage lasts for around 10 days, and the larva stage lasts for around 30-35 days.
• The larva of the silkworm is known as a caterpillar and is in the most active stage of its life cycle.
• The larva accumulates all the nutrient elements needed for the later stages to develop.
• There are five instar stages in the larva stage, during which it undergoes four molting cycles.
• Caterpillars are cylindrical, slippery, and approximately 4-5 cm long.
• One pair of silk glands gets developed in the silk glands, which are a conversion of salivary glands.
• In the larva stage, it actively eats leaves of the mulberry and stops eating food when it gets fully developed.
• At this time, it wraps around itself with silk threads and makes a cover named cocoon, and gets converted into a pupa.
• Pupa is called Chrysalis.
• After 10-12 days, the pupa melts the cocoon and comes out in the form of an adult moth.

Cultivation Process of Silkworm

(i) Rearing of silkworms:

• Includes all activities from egg giving to cocoon formation.
• Appropriate and phased care is important for successful rearing.
• Grainage Technology is essential for rearing.

(ii) Grainage Management:

• The objective is to sustain the fundamental qualities of silkworm species.
• Silk worm eggs must receive complete nutrition and care for successful rearing.
• Cocoons are formed from caterpillars and are separated by sex.
• Loose cocoons are used for egg production and pebrine disease is checked using a detecting machine.

(iii) Supply of seeds to rearers and commercial rearing:

• Supply of eggs or 2nd instar worms.
• Care for 1st, 2nd, and 3rd instar worms should be done carefully.
• Rearing of 4th and 5th instar caterpillars is done in nylon trays for high-quality cocoons.
• Appropriate temperatures are necessary for each instar stage.

(iv) Spinning of Cocoons:

• Fully developed worms stop the intake of food and start excreting sticky fluid from silk glands.
• Moved to spinning tray and kept diagonally towards the sun.
• After 3 days, the cocoon is formed.

(v) Method of obtaining silk worms from cocoons:

• “Stifling” refers to the process of killing silkworms inside their cocoons by applying heat or chemicals.
• “Reeling” refers to the process of unwinding the silk filaments from the cocoons of the silkworms.
• “Spinning” refers to the process of twisting the silk filaments together to form a thread, which can then be used for weaving or knitting fabrics.

Diseases of Silkworm

1. Pebrine

It is caused by a protozoan called Nosema bombycis. Pebrine typically occurs during the rainy and winter seasons, and it can be transmitted to the offspring through transovarial means.

2. Flecherie

Bombysepticus are worms that are affected by a bacterial disease syndrome known as Flecherie. The disease is caused by various viruses, including Infectious Flecherie Virus, Densonucleosis Virus, and Kenchu Virus.

3. Muscardine

The most prevalent and frightening disease in silkworms is caused by Beauveria bassiana, a fungal pathogen. The growth of fungal spores is facilitated by high humidity levels above 80% and low temperatures ranging between 19-22°C during rearing.

4. Grasserie

Grasserie, also known as Nuclear Polyhedrosis, is a disease caused by a baculovirus. While this disease is present year-round, it is more prevalent during the rainy summer months.

Predator of Silkworm

1. Uzi fly

Exorista bombycis is a parasitic fly that targets silkworms. The female fly deposits her eggs on the worm’s outer layer, and once the eggs hatch, the resulting maggots burrow into the larval body and consume its tissue.

Download Sericulture Notes PDF

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