Rearing of Silkworm (Bombyx mori) for production of silk

Silkworm (Bombyx mori) belongs to family Bombycidae of order Lepidoptera, is a great source of natural silk. Rearing of silkworm for the purpose of silk production is called Sericulture.

Sericulture is very important cottage industry that can be done in the people’s home. India and China produce about 60% silk. In case of Sericulture, this industry provides a high employment in the society. This also requires a very low investment and produce a high return.

Moriculture:

Cultivation of mulberry is called Moriculture. Silkworm feeds on Mulberry leaves. Mulberry tree can survive for 15-20 years. According to some estimate 12-15 thousand are invested which give 30-40 thousand per acre in return.

Another important aspect is that:

• It is human friendly.
• ideal for weaker section of poor society.
• Eco-friendly provide vibrancy to the village economics like Cocoon grower, reeler, twister, weaver and trader.

Rearing Procedure: Equipment’s:

• Trays
• Mesh
• Chopper and Chopper board
• Basket
• Hygrometer
• Thermometer
• Rearing stand
• Mountages
• Sprayer

Disinfection of Equipment’s: 

There are two methods to disinfect the equipment’s;

PHYSICAL METHOD:  This method involves Sun drying & Steaming.

CHEMICAL METHOD: In this method 2% formalin is used. Wash the equipment’s with formalin and then you have to dry.

Life Cycle: Total life is about 6-8 weeks.

Eggs:

Eggs require dark place and sharp light for hatching. Firstly, the eggs are   placed in dark place for 2 days when their colour is changed then placed these eggs in sharp light because they are stimulated by light for hatching.

Eggs hatch within 7-10 days. In One packet 20-25 thousands of eggs are present, the cost of local eggs is 300-500 Rs.per packet while the cost of Imported eggs is about 2500-3000 Rs. Per packet.

Transportation:

To transport the eggs temperature is required about 24-25 degree Celsius and Humidity is 70-80%.

Larvae: For Ist instar larvae:

We have to shift them into the trays (place larvae on mesh), leaves should be tender, succulent, green, rich in sugar content and less fiber for 1^st,2nd and 3^rd larval stages.

Moulting:

1^st moult occurs within 3 days. 2^nd moult occurs within 5 days.

3^rd moult occurs within 9 days. 4^th moult occurs within 11 days.

Total larval stage is about 20-33 days.

Space Requirement:

For 1^st instar larvae                 24 sq.ft to avoid overcrowding.

For 2^nd instar larvae                40 sq.ft

For 3^rd instar larvae                 80 sq. ft

For 4^th instar larvae                 250 sq. ft and

For 5^th instar larvae                 300-500 sq.ft area is required.

Food Requirement:

For 1^st , 2^nd and 3^rd instar larvae, leaves should be free from dust and moisture and harvest after 9:00 am.

For 1^st instar larvae require 5 kg leaves per packet.

For 2^nd instar larvae require 10 kg leaves per packet.

For 3^rd instar larvae require 15 kg leaves per packet.

For 4^th instar larvae require 109 kg leaves per packet.

For 5^th instar larvae require 400 kg leaves per packet.

Note: For full packet 500-600 kg leaves are required in its whole cycle this means 15-16 Mulberry trees.

Mounting:

Transferring of mature silkworm to the cocoon frame is called Mounting. When mature after 4-5 days; after 4^th moulting the place where they had to rear. They start to search the cocoon frame and they stop feeding.

They produce the silk that is a protein material which is stored in internal middle silk gland, after the glands they come out from the spinneret and anterior duct these are the openings.

Silk comes from spinneret that cement the filament. That protein is of two kinds:

• Fibrion
• Sericin

If Sericin is removed, this will cause 30% reduction of weight of that filament.

Carefully provide cocoon frame to avoid:

• Double cocooning.
• Stained cocooning.
• Urinated cocoon).

Be careful regarding the spacing approximately 40-50 worms per sq. ft to avoid double or stained cocooning. Number may vary depending upon cocoon frame and species of the larvae.

Types of Cocoon Frames:

• Plastic Mountages
• Bamboo stick Mountages
• Straw Mountages
• Bottle brush
• Revolving Mountages

Pupae:

Pupa when make cocoon, this process takes about 48hours. Pupal stage last for 10-14 days.

Cocoon:

They Ooze out material in this, this may move its head like 8 shape and this happen 70-80 times per minute. 1 Cocoon; its thread is 1.5km or 1-mile long.

Layers of Cocoon:

• Cocoon has 3 layers:
• Outer floss
• Middle compact layer
• Inner pelade

Characteristics of Layers of Cocoon

• Outer floss layer:

1. This is not reelable.
2. Incompact

This outer floss makes about 3.5-4% of total weight of cocoon.

• Middle compact layer:

1. This layer makes the thread.
2. Reelable have many sub layers

This make approximately 91% of total weight of cocoon.

• Inner Pelade:

It is also called ‘pupal shirt’.

• Play significant role in metamorphotic process.

This layer makes approximately 5-5.5% of weight of cocoon.

Harvesting the Cocoon:

You have to harvest the cocoon manually after 7-9 days. In advanced countries by some machines. Before adult emergence, you have to kill the pupae because emergence of adult will damage the cocoon.

• Sun Heating.
• Hot Water Treatment.

Cocoon Damaging:

• Some predators, parasitoids and some beetles (Family: Dermestidae) damage the cocoon.
• Larval parasitoid: Uzifly is larval parasitoid.
• Some Ants, wasp and spiders that attack mostly on 1^st instar larvae and also some grasshopper that attack on mature larvae.

Adult:

Adult moth can live 5-10 days.

Bed Cleaning:

All these materials should have to be removed present in culture on regular basis like:

• Diseased larvae
• Excreta
• Rejected Leaves
• Dead leaves

Because they may cause problems like

• Fermentation
• Humid conditions
• Diseases and
• Temperature as well.

How to do cleaning? 

For 1^st instar larvae= once cleaning. For 2^nd instar larvae= twice cleaning (once pre-molting and once before next molting). For 3^rd instar larvae thrice times cleaning (once after molting and once before next molting and one in middle of them).

During 4^th instar larvae and 5^th instar larvae bed should be cleaned on daily basis. If you are going to rear on floor you have to do cleaning once in one instar.

Disease of Silkworm: 

Viral Disease: 

• Grasserie:

This is the viral disease that create problem for silkworm. Borelina virus:In this case, larvae become restless, sluggish, swollen and milky fluid Oozez out.

Bacterial Disease: 

• Flacherie: 

This comes from bacteria and also from virus. For example; BT and Streptococcus spp and also Flacherie virus. In this case, larval growth stunted and they excrete juicy material from the body and emit foul smell from the body.

Fungal Disease:

• Beuveria bassiana:

In this case, spores grow on larval body and this may come to contamination within 3-4 days. They kill the larvae.

Protozol Disease (Pebrine Disease)

• Nosema bombycis:

In this case, stunted growth of larvae. Black spots, undersized, underweight, slow growth of the body and appetite is poor.

Management:

• Proper cleaning is one of the best important step.
• Eggs should be healthy.
• Disinfection of all the equipment’s or materials which are used in culture.
• Leaves should be clean, not contaminated with dust, disease or any moisture.

• Successful Rearing of Silkworm (Bombyx mori) to get F1 Generation Under Laboratory Conditions.

Authors: Muhammad Ahmad, Arzlan Abbas, Muhammad Umer, Muhammad Atif, Muhammad Ayoub and Zain-ul-abidin Gilani University of Agriculture Faisalabad, Pakistan.

Corresponding Author: Muhammad Ahmad