The improved bivoltine hybrids namely, CSR2 x CSR4 and double hybrid (Krishnaraja) are recommended under IVLP.
From hatching to its full-grown stage, the silk worms pass through five instars and the worms up to stage two are called young age worms or chawki. As they are susceptible to infections and vulnerable to adverse weather conditions, special care is required for rearing of chawki. Hence, it is advisable to obtain silkworm reared under controlled conditions in separate chawki rearing centers. The package of practices for chawki rearing is entirely different from late age rearing.
Rearing of late age worms begins from third instar. These worms are voracious feeders. Various practices required for rearing are indicated below:
Mulberry silkworm rearing, being completely domesticated, demands specified environmental conditions like temperature (24-28 C) and relative humidity (70-85%). It is therefore necessary to evolve measures for economic cooling through selection of proper material for wall and roof fabrication, orientation of building, construction method, design, etc. Further, enough space must be available to carry out leaf preservation, chawki rearing, late age rearing and moulting. It should also be convenient enough to conduct effective cleaning and disinfection.
The size of the rearing house depends upon the quantum and type of rearing. A floor area of 400 sq ft. can provide rearing space for 100 dfls (dfl: Disease Free Layings; 1 dfl = 500 larvae)
The late age silkworms do not tolerate high temperature, high humidity and poor ventilation. Hence, the rearing house should have cross ventilation facilities to bring down the room temperature and for removal of vapour and harmful gases generated from large quantities of excreta produced by silkworms. The minimum requirement of equipments for 100 dfls (50,000 larvae) is given in Table .
Table : Rearing appliances required for rearing 100 dfls (50, 000 larvae)
|1||Shoot rearing rack (40’ x 5) 5 tiers||1|
|2||Rotary mountages or chandrike||35|
Disinfection of rearing house and appliances should be made twice before rearing that is once with 5% bleaching powder (immediately after the completion of previous crop) and another time with 2.5% Sanitech (Chlorine di-oxide) solution just 2 days before the next crop. The schedule suggested for disinfection is given in Table 2.
Schedule of disinfection for rearing house and appliances
|Day||Order of work||Details of work|
|After the completion of previous rearing||1||Collection and burning of diseased larvae and melted and flimsy cocoons.|
|2||Flaming the floss of rotary mountange and disinfection by fumigation|
|3||First disinfection of rearing house and appliances|
|5 days before brushing||4||Cleaning and washing of appliances|
|5||Sun drying of appliances|
|4 days before brushing||6||Disinfection of rearing with 0.3% slaked lime (optional|
|3 days before brushing||7||Second disinfection of rearing house and appliances.|
|2 days before brushing||8||Dusting disinfectant in front of rearing house and to the passage|
|9||Open the windows of rearing house for ventilation|
|1 day before brushing||10||Preparation for brushing|
In this method of silkworm rearing, the last 3 stages of rearing will be conducted by giving mulberry shoots instead of individual leaves. This method is the most economical method of rearing, as it helps to save about 40% of rearing labour. The other advantages are,
Vijetha, Vijetha Green and Ankush are the silkworm body and rearing seat disinfectants for the prevention of silkworm diseases. The method of usage is as follows.
Table 3: Schedule and quantity to be dusted (for 100 dfls)
|Dusting time||Disinfectant||g/sq.ft bed area||Quantity required for 100 dfls|
|After III moult before resumption of feeding||Vijetha/Vijetha Green/Ankush||5||900|
|3rd day of IV instar*||Vijetha supplement||3||600|
|After IV moult before resumption of feeding||Vijetha/Vijetha Green/Ankush||5||1200|
|2rd day of V instar*||Vijetha supplement||3||1300|
|4th day of V instar||Vijetha/Vijetha Green/Ankush||5||3000|
|6th day of V instar*||Vijetha supplement||3||1800|
Note: Vijetha supplement is recommended for the use during rainy season and winter months to control muscardine.
To obtain such quality cocoons, mounting the silkworm larvae at the appropriate time and good quality mountages are essential. In the fifth instar on seventh day silkworms enter into maturation and stop feeding and begin to search place to build the cocoons. Such larvae are picked immediately and mounted on to the mountages. Care should be taken that the number of larvae on mountages must not exceed the capacity of each mountage. When the larvae are in spinning stage, the room temperature of 24°C and 60-70 % of relative humidity along with good aeration facility are to be provided. Rotary mountages are recommended for the production of better quality cocoons. About 35 sets of rotary mountages are required for mounting worms of 100 dfls. For hanging rotary mountages, a separate mounting hall or verandah is required.
Harvest cocoons on 6th day. Remove defective cocoons. After sorting out the defective cocoons grade the cocoons according to the quality. In winter, delay the harvest by one day.
Transport the cocoons during cooler hours of the day and market on 7th day. Cocoons need to be loosely packed in nylon netted bags of 30~40 kg capacity and transported in vehicle having shelves/partitions so that pressing of cocoons can be avoided.
The average yield is 60-70 Kg from 100 dfls. About 700-900 Kg cocoon can be harvested from one acre of mulberry garden in a year.