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INTRODUCTION

  • Definition
  • Sericulture is scientific rearing of silkworms for the production of silk fiber.
  • Key points
  • “Seri” = Silk, “Culture” = Rearing
  • Combines agriculture (mulberry cultivation) and insect rearing.
  • Produce high-value natural fiber.
  • A rural cottage Industry supporting farmer.

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History of sericulture��

  • Originated in China (~2700 BC)
  • Discovered by Chinese empress Leizu.
  • Spread to India via Silk Road.
  • India and China are top silk producers today.
  • Nepal, practiced in hilly regions for small-scale production.

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Types of silk�

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SILK TYPE

SILKWORM

HOST PLANT

DISTRIBUTION

Mulberry silk

Bombyx mori

Morus alba

M. Indica

M.Serrata

M. Lattifolia

Europe

USA

China

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Tasar silk

Antheraea mylitta

Terminalia tomentosa(asan or yen)

T. Arjuna(arjun)

Shorea robusta(sal)

Mid-hills and inner terai region. Like:kathmandu valley, pokhara(kaski).

In inner terai:Dang, chitwan

Muga silk

A. Assama

Machilus bombycina(som)

Litsaea polyantha(soalu)

Brahamaputra valley

Eri or errandi silk

Philosamia ricini

Castor, Ricinus communis

Assam and eastern parts of india.

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Order: Lepidoptera �Family: Bombycidae�

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Mulberry Plant (Host Plant)

  • Primary food of silkworm.�High protein content → better silk.�Major species:�Morus alba�Morus indica�Morus serrata�Climate: 24–28°C, 600–2500 mm rainfall.�Soil: Well-drained loamy soil.

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Life Cycle of Silkworm (Bombyx mori)

  • The silkworm life cycle consists of 4 stages:
  • Egg�Larva�Pupa�Adult moth
  • This is called complete metamorphosis.
  • The total life cycle is completed in about 45–55 days.

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Figure: life cycle of silkworm

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Egg Stage

  • Adult female moth lays 300–500 eggs.�Eggs are very small, oval, and yellow/white.�After some time eggs turn grey before hatching.�Incubation period: 10–12 days.
  • Temperature required: 24–25°C.

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Larval Stage (Silkworm Stage)�This is the feeding and silk-producing stage.

  • Duration:
  • 20-25 days.
  • Instars:
  • Larva passes through 5 instar stages and 4 molting stages.

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Instar

Duration

Feeding

1st instar

3-4 days

Tender leaves

2nd instar

3-4 days

Tender leaves

3rd instar

4-5 days

Medium leaves

4th instar

5-6 days

Mature leaves

5th instar

6-8 days

Large quantity leaves

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Molting:

  • Molting is the process by which an insect sheds its old outer skin (cuticle) and forms a new larger skin to allow growth.
  • Silkworm larva molts 4 times.�Between each molt, the stage is called an instar.�So silkworm has 5 instars and 4 molts.

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What happens during Molting?

1.During molting:�a.Larva stops feeding.�b.Becomes inactive.�c.Head becomes bigger.�d.Old skin splits.�e.New larger skin comes out.�f.This process is also called Ecdysis.

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Cocoon Formation.

  • After the 5th instar:�Larva stops feeding.�Searches for a place to spin cocoon.�Moves head in figure-8 pattern.�Secretes liquid silk → becomes solid when exposed to air.�Forms cocoon in 2–3 days.�Silk filament length: 800–1500 meters.�Inside cocoon larva becomes pupa.

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Pupal Stage

  • Duration: 10–14 days�Transformation stage.�Larva changes into adult moth.�No feeding or movement.�Important in sericulture:�Before moth comes out, cocoon is stifled (heated).�Otherwise moth cuts cocoon and silk thread breaks.

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Adult Moth Stage

  • Adult moth comes out by breaking cocoon.�Cannot fly.�Does not eat.�Lives only 3–5 days.�Male and female mate.�Female lays eggs → Life cycle repeats.
  • Lays 300–500 eggs.

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Requirement for Producing 1 kg of Raw Silk

S. N

ITEMS�

Quantity Required for 1 kg Silk

1

Mulberry leaves

20 – 25 kg

2

Silkworm eggs

30 – 35 g (≈ 30,000 larvae)

3.

Cocoons

6-8 kg

4.

Number of cocoons

3000-5000

5.

Raw silked produced

1 kg

6

Rearing period

45-55 days

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Silkworm Rearing Process

  • Rearing House Preparation: Clean and disinfect, maintain 25–28°C, 70–80% humidity.�Brushing: Transfer newly hatched larvae to trays.�Feeding: Fresh mulberry leaves 4–5 times/day.�Cleaning Beds: Remove leftover leaves and feces.�Mounting: Prepare for cocoon spinning.

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Cocoon Formation

  • Larvae stop feeding.�Spin silk by moving head in figure-8 pattern.�Cocoon forms in 2–3 days.�Silk filament is continuous.

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Harvesting Cocoons

  • Collect 5–7 days after spinning.�Good cocoon characteristics:�Hard, compact, uniform.�No holes.�Golden or white color depending on silk type.

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Stifling

  • Definition: Killing pupa inside cocoon.�Methods: Sun drying, steam, hot air.�Purpose: Prevent moth from breaking silk filament.

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Reeling

  • Definition: Unwinding silk from cocoon.�Steps: Boil cocoon → find filament end → unwind → combine threads.�Produces raw silk.

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Silk Processing

  • Throwing: Twisting threads for strength.�Weaving: Make fabric.�Dyeing: Color silk.�Finishing: Smooth and polish.

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Diseases of Silkworm

Disease

Cause

Symptoms

Pebrine

Protozoa

Small black spots on larvae

Grasserie

Virus

Swollen, shiny larvae

Flacherie

Bacteria

Softening, foul smell

Muscardine

Fungus

White powdery coating

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Common Silkworm pest

Pest Name

Type

Stage affected

Effect on silkworm

Control measure

Uzi Fly (Exorista bombycis)

Insect (Diptera)�

Larvae

Maggots burrow into silkworm, consuming it from inside.

Maintain hygiene, remove infected worms, use light traps.

Silkworm Mite (Trombidium spp)

Arachnid

Larvae

Sucks body fluids, weakening or killing silkworm

Clean rearing house, spray approved insecticides.

Termites

Insect (Isoptera)

Indirect(affect leaves)

Eat mulberry leaves, reducing silkworm nutrition

Store leaves in termite-free containers, keep storage dry.

Ant

Insect (Hymenoptera)

Larvae

Attack silkworms in crowded traits

Elevate trays, maintain cleanliness.

Rodents(rats and mice)

Mammals

All stages

Consume silkworms and mulberry leaves

Use traps, maintain clean rearing house.

Predatory Insects (Ladybugs,Beetles, wasp)

Insect

Egg, larva, cocoons

Attack eggs, larvae, or cocoons

Remove predators, use netting or barriers.

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Prevention Methods of Silkworm Diseases

  • Disinfection of rearing house is essential to prevent silkworm diseases.�Disease-free eggs should be used for silkworm rearing.�Proper temperature and humidity must be maintained.�Clean mulberry leaves should be fed to silkworms.�Regular bed cleaning prevents disease infection.�Diseased larvae should be removed immediately.

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Importance of Sericulture

  • Employment for rural population.�Supports women workers.�Low investment, high profit.�Eco-friendly, sustainable.�Promotes rural economy development.

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Sericulture in Nepal

  • Practiced in hilly regions: Kathmandu, Lalitpur, Kaski, Syangja, Palpa, Ilam.�Supported by government & agricultural programs.�Climate favorable in mid-hills.

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Advantages

  • Short production cycle.�Low land requirement.�High profit per unit area.�Provides eco-friendly fiber.�Supports cottage industry.

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Disadvantages

  • Sensitive to temperature and humidity.�Disease prone.�Labor-intensive.�Requires skill and training.

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Global Distribution of Mulberry Silkworm and Silk Production

  • Major Silk‑Producing Countries (and % of World Production)

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S. N

Country

Approx. % of Global Silk Production (Raw Silk)

1.

China

70% – largest producer of silk in the world

2.

India

~17.5% – second largest

3.

Uzbekistan

3 %

4.

Brazil

~2.25%

5.

Thailand

~1.5%

6.

Vietnam

~1.25%

7.

Japan, Korea, Iran, Nepal, etc.)�

~4.5%

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