Obtaining silkworm larvae or eggs to begin your farm is the most essential step in the process of starting a sericulture (silk production) operation.
In the second part of this series, we discuss how to properly care for the worms and maintain a clean environment on the farm so that you can maximise your production.
Instrumentation, preparatory materials, and sterilisation Silkworms that are bred to have high cocoon thread production can be used in bivoltine sericulture, which raises two generations of silkworms each year. This method results in high-quality cocoons.
Regularly cleaned and sterilised breeding equipment and devices help to keep the environment clean and disease-free.
For instance, the rearing room for young silkworm larvae, the rearing room for grown silkworm larvae, the room for mounting silkworm larvae, and the tools for silkworm rearing (papers for the rearing bed, sheets for the shelves, a cocooning frame) all need to be sanitised and cleaned before, during, and after the rearing process.
Before entering the rearing room, the farmer’s hands must be washed, and farmer’s footwear must be changed to reduce the risk of bringing in bacteria that could cause disease.
The rearing room, as well as the silkworm larvae and beds, need to be disinfected before the first feeding of newly hatched silkworm larvae and before the first feeding of mulberry leaves at each instar. This helps prevent the spread of diseases.
Silkworm eggs and larvae The process of raising silkworms begins with the feeding of newly hatched silkworm larvae. The eggs of the silkworm need to be incubated for about ten days at a temperature of 25 °C, a humidity of 75%, and very particular lighting conditions (16 hours of light to 8 hours of darkness).
In order to ensure a healthy and even birth, the eggs need to be kept in complete darkness for the final two or three days before they hatch. It is essential for the production of highquality cocoons that all the eggs of the silkworm hatch at the same rate. As they develop, the newly hatched worms must consume finely chopped mulberry leaves almost continuously.
However, when the silkworm eggs are not incubated properly, hatching can take place at any time during the process. It is not possible for silkworm larvae to hatch simultaneously if they are poorly managed, and the environment in which they are reared lacks adequate temperature and humidity.
A producer of silkworm eggs will, upon receiving an order from a farmer, hatch the eggs, and then either deliver the young silkworm larvae to a communal rearing facility or deliver them directly to the farmer.
From the time they hatch until they reach the third instar, silkworm larvae are reared. Their growth is affected by the environment, the mulberry leaves, and the way they are raised.
This larvae stage requires a high level of expertise and a healthy rearing environment (first and second instar: rearing temperature of 28 °C, humidity of 75 to 80%, clean condition: disinfection in the rearing room, washing hands and changing shoes, cleaning surrounding the rearing room. Establish a communal rearing house for newly hatched silkworm larvae, care for them until they reach the second instar, and then distribute them to farmers.
There are three distinct phases that occur during the silkworm larvae stage: the young silkworm phase, which begins with the first feeding of newly hatched silkworms and ends with the third instar following the second moulting; the grown silkworm phase, which begins with the fourth instar and ends with the formation of cocoons at the end of the fifth instar; and the mounting phase, which begins with the formation of cocoons at the end of the fifth instar.
Young silkworms, mature silkworms, and silkworms to be mounted should all be raised and mounted in different places and at different times. This keeps diseases from spreading and gives the best possible conditions for rearing.
Third instar silkworms
Silkworm larvae in their third instar are still immature even after being distributed to farmers from a rearing house.
Growers are responsible for maintaining the temperature of 26 to 27 °C, humidity at 75%, and cleanliness of their indoor spaces. It is difficult to maintain the appropriate habitat when third instar silkworms are raised in the same rooms as fully grown silkworms.
Because mounting has such a significant impact on cocoon quality (reliability percentage, contamination, et cetera), it is important to ensure that the environment is properly controlled for temperature and humidity. Ideal temperature is 25°C, and the optimal humidity should be 65% while maintaining good air circulation and ventilation.
By doing so, it is possible to collect silkworm larvae that have reached the appropriate stage of development and that are free from deformities or contamination because the cocoons were mounted in a mounting-specific facility using a mounting container. Urination is quite frequent prior to the formation of the cocoon in mature silkworms.
So, if the silkworms grow at different rates, the urine of the slower-growing silkworms could contaminate the cocoons made by the faster-growing silkworms, and a rise in the temperature of the environment could make it harder to reel the cocoon.
As a result, the space where the silkworm larvae are mounted needs to have adequate ventilation. By thoroughly cleaning and disinfecting the mounting container, you can stop the spread of disease.
The mounting process takes only 1 to 2 days and does not involve any temperature regulation, air movement, or ventilation.
As a result of the rack in the mounting container being slightly too large, it is unable to be turned or maintained at the appropriate distance. This results in poor air circulation and higher humidity, which in turn increase the number of contaminated cocoons. In these conditions, it is difficult to shape cocoons in a uniform manner.
It is necessary to grow silkworms in a uniform manner and improve methods of preserving wooden cocooning frames in the appropriate locations.
Disease in silkworms
Silkworms are susceptible to a wide variety of diseases, including those caused by bacteria, fungi, viruses, and even pebrines. Even in a sterile environment, with clean containers and eggs, pebrine, a disease that spreads through the ovaries, can have a significant negative effect on the sericulture industry.
Pebrine has a major negative impact. Due to these factors, it is of the utmost importance that the mother moth eliminates any pebrine that may be present during the phase of silkworm egg formation. If, upon examination, it is discovered that a mother moth has microsporidia, then any eggs that she lays should not be used because they could be contaminated.
Pebrine presents a potential for contamination due to the limited frequency of mother moth inspections. Additionally, a sanitary rearing environment is not always maintained, such as through the cleaning of the silkworm room and its tools. This leads to concerns over a possible decrease in cocoon yield, and in extreme cases, there is no harvest at all due to the spread of silkworm diseases.
Silkworm larvae initially have a good appetite and eat voraciously until its final stage. After maturing, larvae search for suitable pupation sites. Silkworms shrink and become translucent at this stage. These mature larvae secrete saliva from their two salivary glands to cocoon themselves. When exposed to air, saliva becomes silk. Cocoons are usually spun in two to three days.
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