GOVERNMENT OF TAMILNADU
DEPARTMENT OF SERICULTURE

Silkworm Egg Production

 

            Success of sericulture depends on quality silkworm eggs. Therefore, management of seed production, interalia transportation and incubation play important role on overall return. To produce quality seed, it is very important to adopt scientific methods of egg production right from seed crop rearing to egg incubation.

 

Disinfection of grainage and implements

            The grainage rooms along with its appliances should be thoroughly disinfected prior to commencement of operation and kept ready to receive seed cocoons. A day before disinfection, the rooms and appliances are to be washed with 5% bleaching powder solution and the appliances are to be sun dried for 3-4 hours. A day after, the rooms and appliances should be properly disinfected with a mixture of 2 % formalin, 0.5 to 1 % lime and 0.05% detergent solutions. Room to be disinfected at the rate of 1 litter per square meter floor area.

 

Transportation of Seed Cocoons

            The seed cocoons are to be always loosely packed either in perforated plastic crates or bamboo baskets and transported to respective destinations during cooler hours of day.

 

Pupal examination

             Before selection of seed cocoons, it is very important to know the disease freeness of a lot, melt, filmsy and good cocoons are also to be separated. The gut portion is taken out and subjected to microscopic examination. In case there is incidence of pebrine, the lot has to be rejected. Before the arrival of new lots, it is very important and essential to disinfect the contaminated rooms.

 

Preservation and protection of seed cocoons

            Immediately after the receipt of seed cocoons, they are to be spread on trays in a single layer to facilitate good aeration. Sorting of seed cocoons like melt, uziinfested, filmsy and those which are not conforming to the characteristics of parent races are to be taken out and rejected. The healthy seed cocoons alone should be preserved in trays for further processing. There should be cross ventilation in the preservation room, 25 +- 1o C temperature, 75 +- 5 % relative humidity, 12 hour light and 12 hour dark conditions to be maintained in the cocoon preservation rooms. Complete darkness to be maintained on the previous day of emergence , to avoid irregular emergence of moths.

 

Early eclosion / artificial eclosion / forced eclosion of moths

            This helps in determining the disease freeness of a batch and helps in minimizing the loss to grainage.

 

Early moth eclosion box

            A simple box made up of wood and plywood sheet with a glass door having dimension 90 x 75 x 60 cm is used. The bottom is fitted with asbestos sheet. A heating element is connected to the electric main through a thermostat (0 – 60 o C ). On the top of the box at the centre, a 15-cm diameter ventilator covered with wire mesh is provided. It is fitted with sliding top to regulate ventilation. At the bottom of the box and on the lower portion of sidewalls, small holes are drilled to facilitate aeration. For reading the temperature, a thermometer is fixed from inside of glass door. Within the box, a portion has been made to place 4-5 plastic trays in two tiers for keeping seed cocoon inside.

            For early emergence of moths, 50-60 seed cocoons are taken from individual lots and placed into an artificial eclosion box. The temperature in the box is adjusted to 32-33 o C with the help of thermostat. This accelerates the development of pupae and moth emerges early. The early-emerged female moths of respective lots are taken and subjected for microscopic examination to know the disease freeness of lots.

 

Synchronization of emergence of moths, pairing, depairing and oviposition

            Before the expected day of emergence of moths, the cocoon preservation rooms should be kept dark. In case of variation in development of male or female pupae, the development of male pupae can be arrested by preserving them at 5-7 o C and 75 +- 5 % relative humidity for 3-4 days. Only healthy and active moths are taken for pairing. After 1-2 hours of emergence, the male and female moths of respective combinations are allowed for 3.5 to 4 hours of pairing. At the time of depairing, the male and female moths are to be moved side ways so that the moths are separated easily without causing injury to reproductive organs. The matted female moth are taken in a separate container and induced for urination. Moths are placed on egg sheet and covered with cellules and kept in dark condition for oviposition. Under proper preservation (5-7 o C) male moths can be used for second pairing by giving 1-2 hours rest. Throughout the process of pairing, depairing  and oviposition, optimum temperature of  25 +- 1o C and relative humidity of 75 +- 5 % should be maintained.

 

Surface sterilization of silkworm eggs

            After ascertaining the disease freeness of layings, egg sheets are dipped in 2 % formalin for 10-15 minutes. This helps in removal of pathogens adhering to the eggshell and further prevents secondary contamination. Washing of eggs in formalin solution helps in firm adherence of eggs to the sheet.

 

Incubation of silkworm eggs

            Incubation facilities uniform development of embryo. In addition, it greatly influences the voltinism of the eggs in succeeding generation, larval growth and success of cocoon crop. Therefore, the eggs are subjected to ideal conditions of incubation.

            Optimum temperature of 25 +- 1o C and relative humidity of 75 +- 5 %, 16 hours of light and 8 hours of darkness are ideal. During the pinhead stage or before two days of hatching, the eggs are black boxed to aim at uniform development of embryo and hatching of larvae at a time on a single day.

 

Loose egg preparation

            Loose eggs are getting popular for obvious advantages such as (a) standard / uniform egg number (irrespective of the race, season, zone) (b) increased egg recovery and (c) easy and better management.

 

Advantage of loose eggs

·     Superior quality

·     Uniform and known quantity irrespective of race / season / zone / grainage   etc.,

·     Enables scientific evaluation

·     Increased egg recovery

·     Increased hatchability

·     Economical seed production

·     Efficient surface sterilization

·     Easy acid treatment of bivoltine eggs.

·     Unfertilized eggs can be eliminated (in bivoltine only)