Silkworm Rearing, Mounting, Harvesting, and Marketing of Cocoons

Silkworm rearing involves nurturing silkworms through different life stages to produce high-quality cocoons. This process is divided into two main phases:

1. Young Age Silkworm Rearing (Chawki Rearing) – From hatching to the second moult.
2. Late Age Silkworm Rearing – From the third to the fifth instar (final) stage.

1. YOUNG AGE SILKWORM (CHAWKI) REARING

This stage requires high humidity (80-85%) and optimal temperature (26-28°C). Proper care and nutritious mulberry leaves are crucial for healthy growth and disease resistance.

Selection of Leaves:

• Tender Leaves: From brushing to the end of the second age, feed the larvae with tender leaves to support rapid growth.
• Leaf Selection: Choose the largest glossy leaves from the 3rd or 4th position from the top of a fully grown mulberry branch. The next 6 to 8 leaves are suitable for rearing young age worms up to the second moult.
• Leaf Size: During the second age, chop the leaves into small pieces of about 0.5 to 1.0 square cm.
• Illustration: Leaves are selected from the top portion of a fully grown branch, as they are tender and rich in nutrients.

Leaf Preservation:

• Moisture Retention: Silkworms thrive on succulent leaves that are nutrient-rich and high in moisture. To maintain freshness, wrap harvested leaves in a wet gunny cloth.
• Leaf Chamber: In hot and dry climates, store leaves in a leaf chamber lined with a wet gunny cloth. Spray water frequently to retain moisture.

Cleaning:

• Purpose: To remove silkworm excreta and leftover leaves, maintaining hygiene and preventing disease outbreaks.
• Cleaning Frequency: First Age: Once, a day before moulting. Second Age: Twice – once after resuming feeding and once before the second moult.
• Procedure: Spread a net (mesh size: 0.5 x 0.5 cm) over the rearing bed and provide fresh leaves on top. Larvae crawl through the net to reach the new leaves. Transfer the net along with worms to a clean tray. Discard the leftover litter and leaves.

Moulting:

• Moulting Care: During moulting, worms are highly sensitive and should not be disturbed. Correctly identifying moulting time is crucial to stop feeding, which ensures uniform growth.
• Rearing Bed Management: Keep the rearing bed thin and dry by applying lime (30 – 50 g/m²) to maintain dryness and aeration.

2. LATE AGE SILKWORM REARING

Late age rearing covers the third, fourth, and fifth instar larvae stages. This phase requires a temperature of 23-25°C and lower humidity (70-75%).

Feeding and Leaf Selection: Leaf Type: Third and Fourth Age: Medium maturity leaves (6th leaf onwards) are suitable Fifth Age: Coarse leaves are fed for higher consumption. Avoid over-matured or yellow leaves to prevent disease outbreaks.

Bed Disinfectants:

• To maintain hygiene and prevent disease, use bed disinfectants like TNAU Seridust, Resham Jyothi, Vijetha, or Sajeevini.
• Application Rates (per 100 dfls):

Moulting Management:

• Pre-Moult Preparations: Spread larvae evenly on the rearing bed 6-8 hours before moulting. Maintain good ventilation to prevent excess humidity.
• Humidity Control: During rainy or winter seasons, apply lime powder 60 minutes before resuming feeding to reduce dampness.

3. MOUNTING

After the final instar, worms cease feeding and are ready to spin cocoons.

Process: Ripened Worms: Slightly translucent with raised heads, searching for a place to spin. Transfer to Mountage: About 800-900 worms per square meter. Use 30-40 chandrakis (mountages) for 100 dfls. Precautions: Do not delay mounting, as ripened worms may waste silk. Keep mountages in shaded, well-ventilated areas to facilitate proper spinning.

Care During Spinning:

• Temperature and Humidity: Maintain 60-70% relative humidity to prevent filament thinning and thickening. Ensure proper ventilation and moderate lighting to avoid crowding and double cocoons.
• Ant Protection: Apply malathion 5% dust or lakshman rekha at the base of the mountage to protect against predatory ants.
• Maintenance: Remove dead worms and non-spinners on the 2nd day of spinning. Incline mountages to drain excreta and urine, preventing cocoon staining.

4. HARVESTING

• Timing: Spinning is completed in 2-3 days, but harvesting should be done on the fifth day (7th day for bivoltine hybrids) when pupae are fully formed and hard.
• Precautions: Avoid harvesting when the pupa is amber-colored. Remove dead and diseased worms before harvesting.
• Marketing: Cocoon marketing should be done on the sixth day (8th day for bivoltine hybrids).

5. SHOOT REARING FOR LATE AGE WORMS

Advantages: Labor savings of up to 70%. Leaf saving of 15-20%. Better cocoon quality and production. More organic matter production (up to 18 tonnes per hectare per year). Reduced contamination and disease risk. Disadvantages: Requires 30% more rearing room space. Bed refusals are not available as cattle feed. No availability of planting materials (cuttings).