Chawki Rearing

Last modified at 24/08/2016 13:41 by System Account

Chawki Rearing

Rearing of young age silkworms up to 2nd moult is called as chawki rearing. This stage of larvae requires ideal environmental conditions, tender mulberry leaves. Robust growth and development of chawki larvae make them resistant to diseases and more stress tolerant during later stages of development.

Silkworm layings should be procured only from licensed seed preparers which are tested and certified as disease free layings (dfls). Under normal recommended cultivation practices of mulberry 250-300 dfls can be brushed per crop per acre. Silkworm layings have to be transported in egg carrying boxes, during cooler hours of the day from the grainages to the place of rearing. Transportation in egg transportation boxes avoids exposure of layings to extreme temperatures and humidity.

During incubation period care should be taken to preserve the layings in a disease free environment, with high relative humidity of more than 80% and temperature of 24-25� C. The embryo inside the eggs grows healthly utilizing the reserved food materials in the yolk and prepares to hatch on the 10th day of egg laying. To maintain the ideal temperature, humidity and hygiene during incubation, several techniques are recommended;

  1. The layings after procuring from the grainages are spread in a single layer on a paraffin paper spread rearing trays. Wet foam pads are to be placed all around the layings and covered with paraffin paper. This helps to provide ideal temperature and humidity.
  2. Wet Earthern pot: Well baked earthern pot with a wide mouth about 15� diameter is filled with 2-3� wet sand. Egg sheets are tied to a stick and hung 2-3� above the wet sand bed.
  3. Buried earthern pot method: A common round pot having a wide mouth is buried in clean sand up to the neck and sand is made wet. In both the above two cases, the sand is kept wet one day prior to incubation for pre-conditioning. The laying in sheets are tied to a rod/stick and hung inside the pot and the pot is covered with wet cloth. The temperature is reduced by 5 to 10%. Eggs are incubated up to head pigmentation stage and transferred to a black box.

Double walled chamber method:

The chamber is constructed using brick and mortar. A gap of about 3� is left between the inner and outer wall, which is filled with loose and clean sand. The standard size of the outer wall is 6� x 4� x 3�, while that of inner wall should be 4� x 2� x 3�. This chamber should accommodates 5000-6000 dfls.

Incubation of loose eggs:

Loose eggs should be incubated in frames made up of 2cm thick plastic or wood. The outer frame is 36 x 24 cm and the bottom inner frame is 32 x 20 cm and fits perfectly in the outer frame. Loose eggs are spread uniformly in the inner frame covered with a tissue paper and outer frame is fixed to hold the tissue paper. These frames are placed in a rearing tray and covered with paraffin paper. Each frame can hold 50 dlfs loose eggs (20000 eggs).

Black boxing of eggs:

Black boxing technique is subjecting the developing eggs to a totally dark condition, to synchronize the circadian rhythm of the silkworms. This ensures uniform synchronized hatching of eggs. Black boxing should be done on the 8th or 9th day i.e. on the onset of �eye-spot� or �black head� stage. A long paper cover made from black craft paper is used for this purpose. In each cover of 12� x 9� size, 250 dfls packed 5 tissue paper covers containing 50 dfls each is placed inside the black cover. The cover is clipped and kept in the rearing tray surrounded with wet foam pad and covered with aparaffin paper. On the day of hatching, at 7 � 8 AM, the covers are opened and layings exposed to mild light. Within 2 hours all the eggs will hatch. For acid treated bivoltine eggs a minimum of 60 hrs of black boxing and for hibernating eggs 72 hrs of black boxing is required.

Package of Practices for Chawki Mulberry Gardens in Tropics

The silkworm (Bombyx mori L.) is a monophagous and highly domesticated insect. The qualitative and quantitative requirements of the feed for silkworms differ at different stages of larval period. It is generally established that the young age silkworms require mulberry leaf of higher succulence, moisture and nutrient contents, the late age worms feed on coarser leaf with less moisture content. The quality of leaf used for young worms is of greater relevance in view of the influence of chawki rearing on the late age silkworms and ultimately the success of cocoon crop. Hence, production of succulent and nutritious leaf attains greater significance in establishment of the CRCs. On the other hand, growth of chawki mulberry plants should be monitored in such a way as to reduce the coarseness and rate of maturation of mulberry leaf thereby avoiding wastage of the biomass produced from such mulberry gardens.

Keeping in view the delicacy of young age silkworms and their contribution towards the success of cocoon crop, the said technology has been developed at the KSSRDI with suitable cultural practices such as spacing, manuring, irrigation, leaf harvest schedules apart from selection of suitable superior mulberry variety and pruning schedule, for establishment and maintenance of exclusive chawki mulberry gardens, a wholesome package for economization of the chawki leaf production.

By adopting this technology, about 10,000 kg chawki mulberry leaf/0.4 ha (one acre) can be obtained. The leaves are nutritious with about 76-78% leaf-water content, 24-25% soluble proteins and 9-12% soluble sugars which are very crucial for the healthy growth of the young silkworms.

The climatic conditions prevailing in different parts of Karnataka state are found suitable for raising chawki mulberry gardens.

Soil: Exclusive chawki mulberry gardens can be raised in flat and elevated places with red loam, red sandy loam and red clay loam, with a pH range of 6.5-7.5. Gravelly and coarse sandy soils and soils with shallow top soil are not suitable.

Mulberry varieties: S36, M5, �Viswa� and V1 mulberry varieties are most suitable for chawki mulberry gardens.

Planting season: Establishment of plantations during June-August period in moderate climatic zones and September-October period in heavy rainfall areas can be followed. About 120 days old saplings can be used for planting.

Plant spacing: The plant spacing of 60 x 60 cm can be adopted.

Manures:

FYM :

Before planting 

After establishment of the garden

 

20 t/ha         

30 t/ha/yr (in 2 equal split doses), after each base cut

Chemical Fertilizers :

During  establishment  of  the garden  (in 2 split doses)

100:50:50 kg  NPK/ha (in 2 equal split doses)
Annual : After  establishment   of the garden   

240:140:140 kg N PK/ha/yr

(in 4 equal split doses after each pruning)

Pruning: Annual basal cut at 30 cm above the ground, preferably during the onset of the monsoon. Following the 1st base cut and 3 leaf harvests, at an interval of 15 days, 1st middle pruning at 60 cm above the ground has to be done. Followed this, 3 leaf harvests can be made. Again, the same sequence may be followed. Totally 2 base cuts and 2 middle cuts done yearly. After about 20 days of each pruning, weak branches can be removed.

Irrigation: In light sandy loam soils, irrigation at 7-8 days interval may be necessary while in heavy clay loam soils, irrigation at 8-10 days interval may be found adequate. It has been estimated that 1.5 to 2 acre inches of water per irrigation is required. To save irrigation water micro irrigation system can be suitably adopted.

Leaf harvesting and preservation: The leaves to be harvested will be from below the largest glossy leaf which is yellowish green in color. The cardinal point is shoot tips should not be removed during any leaf harvest. From the glossy leaf, about 3 leaves during the 1st (1-3) and about 3 leaves (4-6) during 2nd instar can be harvested. Usually in cool hours (morning and evening) leaf harvest has to be done. The harvested chawki leaves should be preserved in cool and clean (hygienic) placers in order to preserve their succulence.

Plant protection:

Diseases: Powdery mildew, Leaf spot, Leaf rust, Stem canker, Root-rot and Nematode.

Pests: Thrips, Mites, Jassids, Tukra and Leaf roller. Generally for control of fungal diseases spraying of 0.2% Bavistin (Carbendazim) with 15 days safe period and for control of nematode infestation, soil application of Furadon 3G at 6-7 kg/0.4 ha with 45 days of safe period and for control of pests, spraying of 0.1% Metasystax can be employed. But, plant protection measures can be taken only after 2 base cuts and 2 middle cuts and 15-18 days before leaf harvest for brushing.

Advantages:

  • By the adoption of annual pruning schedule of 4 prunings and 12 leaf harvests, higher leaf yield of about 10,000 kg/0.4 ha/yr can be obtained and 60,000 dfls can be brushed/year, at the rate of 15 kg chawki mulberry leaf/100 dfls.
  • Increase in number of harvests and maintenance of vigor of the plants may suitably adjusted by adoption of yearly 4 prunings and 12 leaf harvests schedule.
  • This schedule can be easily practiced by private CRCs/large scale sericulturists.
  • Good quality chawki leaves for every harvest could be produced at an interval of 15 days. The leaves will be rich in leaf-water content and nutrients and when fed to young silkworms, their growth will be best.
  • If a chawki mulberry garden or a plot is divided into two plots/units and the recommended package of practices followed, yearly 24 chawki leaf harvests can be obtained to facilitate regular brushings once in 15 days at CRCs.
  • The advantage of this package is, other than obtaining suitable leaf for chawki rearing, chawki leaf can be produced throughout the year continuously coinciding with the brushing programmes.
  • Conducting late age silkworm rearings with good chawki reared worms will lead to good cocoon production.

Precautions:

  • Adequate irrigation and recommended inputs must be ensured.
  • The cardinal point is shoot tips should not be removed during any leaf harvest.
  • Plant protection measures can be taken only after 2 base cuts and 2 middle cuts and 15-18 days before leaf harvest for brushing.

Brushing of silkworm eggs:

  • At the time of brushing, the mulberry leaf is cut to fine ribbons and sprinkled over the hatched worms to facilitate easy transfer of larvae from the egg sheet to the bed.
  • After half an hour the worms are tapped on the rearing bed in the tray and 0.5 sq.cm cut tender leaves are fed.
  • The size of the bed for 25 dfls should be 25 sq.cm.

Methods of young age rearing: Different methods of young age rearing are in practice. The most common methods are box and stand rearing.

Box rearing:

  • Wooden trays of 4� x 3� x 2� and 4� depth are used.
  • Trays during feeding period are arranged one above the other upto a convenient height. It can increase the temperature/humidity in the rearing bed.
  • Keep the trays in criss-cross condition for 30 minutes before feeding to allow fresh air.
  • 30 minutes before feeding and during moulting period, the paraffin or polythene sheets are removed.
  • Minimum space is requirement.

Stand rearing: Stand rearing is done when optimum temperature and more rearing humidity are available in the rearing room. In this method more rearing space is needed.

Cover rearing method: During the first two instars, the rearing bed of young larvae is covered with polythene sheets both at the bottom and top with four sides wrapped. The size of plastic film is 116 cm x 86 cm (depends on the size of tray), thickness 0.03-0.4 mm. The polythene should be punched and the size of the hole should be 0.15-0.2 mm and distance between the holes should be 1.5-2 cm. The polythene sheet should be transparent.

Feeding/Nutrient requirement for chawki rearing:

  • Chawki worms should be fed with succulent mulberry leaves rich in nutrients and moisture content viz., water content (80%), protein (27%) and carbohydrates (11%).
  • Separate chawki garden with superior mulberry variety like KNG or lchinose are maintained by providing irrigation and inputs such as FYM and chemical fertilizers in the recommended dose (FYM : 40 MT; N:P:K:300:150:150)
  • Select first glossy leaf from the top of branch for 1st feeding at the time of brushing and with the advancement in larval age the first 3-4 tender leaves can be used.
  • Leaf harvest must be done in the morning and evening.
  • Preserve the mulberry leaves in a cool place covered with wet gunny cloth.
  • In dry season, sprinkle water over leaves and preserve them under wet gunny cloth.
  • Chopped leaves should be fed to worms for uniform growth.
  • Three feeding schedule viz., 6 am, 2 pm and 10 pm should be followed.
  • Stop feeding when above 90% worms settle for moult and resume when 95% worms comes out of moult.
  • 30 minutes before feeding, the paraffin or polythene are removed and after feeding the rearing beds are again covered with polythene sheets.
  • The size of the leaf fed should be 1.5 sq.cm. in first stage and increased to 3 sq.cm. as worms advance in age.
  • Size of the leaf should be reduced when worms start settling for moult.

Bed cleaning: Only two cleanings are recommended during second stage and no cleaning in first stage. Cleaning nets are applied on the bed, chopped leaf is fed to worms. Worms crawl through the net. After two hours, worms are transferred to another tray. If cleaning nets are not available, the topmost layer with worms must be taken with a feather.

Spacing: Overcrowding of the silkworms in the early stage leads to sizing and poor growth. Regulate the spacing for the healthy growth of the silkworms. There should be uniform distribution of the larvae in the bed.

Use of bed disinfectant: Dusting of bed disinfectants is important to avoid secondary contamination. The quantity of dusting of different bed disinfectants for 100 dfls is around 50g after 1st moult and 100g after 2nd moult.

Care during moult:

  • Ensure good aeration and dry conditions in rearing bed during moult.
  • Remove the polythene during moult period.
  • Temperature/humidity should be kept 1�C less viz., 26�C and RH 65-70%.

Concept of chawki rearing: To raise a healthy stock of silkworms the system of chawki rearing must be quite effective:

  • Maintenance of optimum temperature/relative humidity.
  • Feeding of nutritious tender leaves.
  • Maintenance of absolute hygienic conditions.
  • For rearing chawki worms experienced persons are needed.

Presently most of the farmers are engaged in self chawki rearing. However, cooperative chawki rearing have the following advantages over existing technology.

  • Ensuring uniform embryonic growth and good hatching.
  • Minimizing the missing larval resulting in higher larval population.
  • Robust and disease free growth of the worms.
  • Prevention of crop loss and stabilization of cocoon crop.
  • Minimization of pest and disease out break by synchronization of crops
  • Crop monitoring is easier and effective
  • Effective utilization of saved labour and time for other activities.
  • Higher cocoon yield of good quality at reduced production cost.
  • By adopting the chawki rearing technology, farmers get 5-6 kg more cocoon yield compared to doing self chawki rearing. In addition to cocoon yield, farmer will be free from rearing activities for about 10 Days. Cocoon production cost reduced and crops will be synchronized.
  • The technology develops co-operations among farmers. This has social impact on villagers. CRCs are back bone of sericulture industry and all the important technologies can be advocated through CRCs. Marketing of cocoons can also be linked through CRCs.

Distribution of chawki worms: Worms in the tray can be rolled along with punched paraffin/old news paper at the base and top. Ends are closed and stapled. Worms should be transported to the rearers house during morning hours and fed immediately with fresh leaves.

Precautionary measures during the rearing of young larvae:

  • Before entering the rearing room, where chawki worms are reared, hands should be washed.
  • Separate footwear should be used inside the rearing rooms.
  • Silkworm litter should not be thrown in the rearing room.
  • Rearing rooms should be kept clean and tidy.
  • Avoid touching the worms.

Standard Chart for young age silkworm rearing (100Dfls larvae)

Larval Stage Age (days) Feeding time

Leaf size in

Sq. Cms

Bed area

(Sqft)

Leaf quantity Remarks

 

 

I

Instar

27-28OC

80-85% RH

 

1

10 A.M

2 P.M

10 P.M

Finely chopped

0.5 x 0.5

0.5 x 0.5

 

4-7.5

 

500 gm Expose layings from black box to light around 7AM. Brush the larvae. Brush the larvae around 9 AMusing finely chopped tender fresh leaves. Make the bed after about 30 minutes, give feeding with cut leaf of 0.5x 0.5

 

2

6 P.M

2 P.M

10 P.M

1.0 x 1.0

1.5 x 1.5

1.5 x 1.5

 

7.5-10.5

 

1,800 Spread the bed half an hour before feeding for drying.

 

3

6 A.M

2 P.M

10 P.M

1.5 x 1.5

1.5 x 1.5

0.5 x 0.5

10.5-15 1,200 Spread the bed half an hour before feeding for drying. Observe for moulting behaviour, reduce the leaf size and quantity appropriately

 

I

moult

 

4

6 A.M

2 P.M

10 P.M

0.5 x 0.5

1.5 x 1.5

1.5 x 1.5

15 200 Stop feeding when about 90% of larvae settle for moult. Break/ Spread the bed gently and apply fresh active lime powder @4-5g/sqft to dry the bed.

 

 

 

II Instar

27-28OC

80-85% RH

 

5

6 A.M

2 P.M

10 P.M

1.5 x 1.5

1.5 x 1.5

2 x 2

15-30 3,500 Give feeding if more than 90% of the larvae are out of moult. Disinfect the larvae/bed before feeding. Clean the bed using net.

 

6

6 A.M

2 P.M

10 P.M

2 x 2

2 x 2

2 x 2

30-45 4,250 Spread the bed half an hour before feeding for drying.
7

6 A.M

2 P.M

2x 2

1x1

45 1,100 Observe for moulting behaviour, if the symptom of moulting is observed reduce the leaf size and quantity, clean the bed before settling for moult.
II moult

 

 

8

10 P.M

6 A.M

10 A.M

2 x 2

-

45 - Stop feeding when about 90% of larvae settle for moult. Spread the bed gently and apply fresh active lime powder.

Isolation Chamber:

Young age rearing is the most important activity in silkworm rearing. A good chawki is the key for a successful crop. However, most of the farmers do not have a separate chawki rearing room.

Realizing the prevailing situation, an isolation chamber has been evolved which helps in providing all the required conditions to a large extent in the farmers rearing houses and chawki rearing centres. It is observed that when chawki is raised in such isolation chambers there is an increased larval and cocoon weight with better survival rate and therefore higher yields.

The isolation chamber can easily satisfy the average farmer as it can easily be accommodated inside his dwelling house. The isolation chamber can be made either with wood or brick masonary. Construction details of a model isolation chamber for a unit of 300 dfls upto 2nd moult is as follows:

The isolation chamber can easily satisfy the average farmer as it can easily be accommodated inside his dwelling house. The isolation chamber can be made either with wood or brick masonary. Construction details of a model isolation chamber for a unit of 300 dfls upto 2nd moult is as follows:

Height : 6�
Width : 4�
Depth : 5�

Door: Single door of 5.5� x 4� with a glass window of 6� x 9� in the centre of the door, at a height of 4.5� to 5� from the floor for installation of wet and dry bulb thermometer from inside the chamber.

Ventilators: Lower two rectangular ventilators of 4 x 9 size. Two circular ventilators of 7 dia size in the roof of the chamber with sliding doors and uzi proof mesh fixed.

Heating facility: To increase the temperature, a 2 KV blowing type heat convector can be fitted to one of the ventilator in the bottom of the chamber. The heat convector is connected to a thermostat to regulate the temperature.
Humidity of the chamber is increased by keeping water in wide tray on the floor of the chamber in addition to the use of wet foam pads around the beds, if necessary.

Rearing stand: Rearing stand of 5.5� height, 2.5� width with 14 tiers with a distance of 4.5� between each tier.

Rearing tray: Standard wooden chawki tray (box) of 3� x 4� x 2.5� size, 14 trays are required per chamber. The bottom and top most trays will serve as dummy trays leaving 12 trays for rearing 300 dfls at the rate of 25 dfls per tray. If the rearing capacity is more, chambers can be constructed side by side.

Temperature and humidity inside the chamber: Maintenance of uniform temperature and humidity is easy inside the chamber, mainly because of the restricted area. When heater is used to increase the temperature, the power consumption is very less as the heater is on, only for few hours per day as compared to continuous functioning outside the chamber. Further, under non-manipulated conditions (when heater is not used) the temperature is uniform without much fluctuation inside the chamber, which is more congenial for the growth of the larvae as compared to wide fluctuations outside.
It is observed that humidity is always on the higher and uniform in the chamber as compared to outside.

Maintenance of leaf quality: The loss of moisture of cut leaves used for chawki rearing is very less inside the isolation chamber mainly because of prevailing high humidity. As a result of this the bed life of leaf is better which enhance the leaf utilization efficiency as reflected by the increased chawki larval weight.

Ventilation management: Proper aeration inside the chamber is achieved through lower and upper ventilators. One of the lower ventilators is closed when the other is fitted with blowing type heater, while the upper ventilators are to be keep open by � of its size during the beginning of the first instar. As the larvae grow, gradually, upper ventilators are opened to � of its size by the end of the second instar. Keep both the lower ventilators open when the heater is not used. All ventilators should be fully opened, half an hour before feeding to facilitate the bed drying, so also during moulting to reduce humidity and to keep the bed dry. Unnecessary opening the doors should be avoided since it affects the uniform maintenance of temperature and humidity and also increases the chances of contamination of dust and pathogens.

 Content Editor

Chawki Rearing

Rearing of young age silkworms up to 2nd moult is called as chawki rearing. This stage of larvae requires ideal environmental conditions, tender mulberry leaves. Robust growth and development of chawki larvae make them resistant to diseases and more stress tolerant during later stages of development.

Silkworm layings should be procured only from licensed seed preparers which are tested and certified as disease free layings (dfls). Under normal recommended cultivation practices of mulberry 250-300 dfls can be brushed per crop per acre. Silkworm layings have to be transported in egg carrying boxes, during cooler hours of the day from the grainages to the place of rearing. Transportation in egg transportation boxes avoids exposure of layings to extreme temperatures and humidity.

During incubation period care should be taken to preserve the layings in a disease free environment, with high relative humidity of more than 80% and temperature of 24-25� C. The embryo inside the eggs grows healthly utilizing the reserved food materials in the yolk and prepares to hatch on the 10th day of egg laying. To maintain the ideal temperature, humidity and hygiene during incubation, several techniques are recommended;

  1. The layings after procuring from the grainages are spread in a single layer on a paraffin paper spread rearing trays. Wet foam pads are to be placed all around the layings and covered with paraffin paper. This helps to provide ideal temperature and humidity.
  2. Wet Earthern pot: Well baked earthern pot with a wide mouth about 15� diameter is filled with 2-3� wet sand. Egg sheets are tied to a stick and hung 2-3� above the wet sand bed.
  3. Buried earthern pot method: A common round pot having a wide mouth is buried in clean sand up to the neck and sand is made wet. In both the above two cases, the sand is kept wet one day prior to incubation for pre-conditioning. The laying in sheets are tied to a rod/stick and hung inside the pot and the pot is covered with wet cloth. The temperature is reduced by 5 to 10%. Eggs are incubated up to head pigmentation stage and transferred to a black box.

Double walled chamber method:

The chamber is constructed using brick and mortar. A gap of about 3� is left between the inner and outer wall, which is filled with loose and clean sand. The standard size of the outer wall is 6� x 4� x 3�, while that of inner wall should be 4� x 2� x 3�. This chamber should accommodates 5000-6000 dfls.

Incubation of loose eggs:

Loose eggs should be incubated in frames made up of 2cm thick plastic or wood. The outer frame is 36 x 24 cm and the bottom inner frame is 32 x 20 cm and fits perfectly in the outer frame. Loose eggs are spread uniformly in the inner frame covered with a tissue paper and outer frame is fixed to hold the tissue paper. These frames are placed in a rearing tray and covered with paraffin paper. Each frame can hold 50 dlfs loose eggs (20000 eggs).

Black boxing of eggs:

Black boxing technique is subjecting the developing eggs to a totally dark condition, to synchronize the circadian rhythm of the silkworms. This ensures uniform synchronized hatching of eggs. Black boxing should be done on the 8th or 9th day i.e. on the onset of �eye-spot� or �black head� stage. A long paper cover made from black craft paper is used for this purpose. In each cover of 12� x 9� size, 250 dfls packed 5 tissue paper covers containing 50 dfls each is placed inside the black cover. The cover is clipped and kept in the rearing tray surrounded with wet foam pad and covered with aparaffin paper. On the day of hatching, at 7 � 8 AM, the covers are opened and layings exposed to mild light. Within 2 hours all the eggs will hatch. For acid treated bivoltine eggs a minimum of 60 hrs of black boxing and for hibernating eggs 72 hrs of black boxing is required.

Package of Practices for Chawki Mulberry Gardens in Tropics

The silkworm (Bombyx mori L.) is a monophagous and highly domesticated insect. The qualitative and quantitative requirements of the feed for silkworms differ at different stages of larval period. It is generally established that the young age silkworms require mulberry leaf of higher succulence, moisture and nutrient contents, the late age worms feed on coarser leaf with less moisture content. The quality of leaf used for young worms is of greater relevance in view of the influence of chawki rearing on the late age silkworms and ultimately the success of cocoon crop. Hence, production of succulent and nutritious leaf attains greater significance in establishment of the CRCs. On the other hand, growth of chawki mulberry plants should be monitored in such a way as to reduce the coarseness and rate of maturation of mulberry leaf thereby avoiding wastage of the biomass produced from such mulberry gardens.

Keeping in view the delicacy of young age silkworms and their contribution towards the success of cocoon crop, the said technology has been developed at the KSSRDI with suitable cultural practices such as spacing, manuring, irrigation, leaf harvest schedules apart from selection of suitable superior mulberry variety and pruning schedule, for establishment and maintenance of exclusive chawki mulberry gardens, a wholesome package for economization of the chawki leaf production.

By adopting this technology, about 10,000 kg chawki mulberry leaf/0.4 ha (one acre) can be obtained. The leaves are nutritious with about 76-78% leaf-water content, 24-25% soluble proteins and 9-12% soluble sugars which are very crucial for the healthy growth of the young silkworms.

The climatic conditions prevailing in different parts of Karnataka state are found suitable for raising chawki mulberry gardens.

Soil: Exclusive chawki mulberry gardens can be raised in flat and elevated places with red loam, red sandy loam and red clay loam, with a pH range of 6.5-7.5. Gravelly and coarse sandy soils and soils with shallow top soil are not suitable.

Mulberry varieties: S36, M5, �Viswa� and V1 mulberry varieties are most suitable for chawki mulberry gardens.

Planting season: Establishment of plantations during June-August period in moderate climatic zones and September-October period in heavy rainfall areas can be followed. About 120 days old saplings can be used for planting.

Plant spacing: The plant spacing of 60 x 60 cm can be adopted.

Manures:

FYM :

Before planting 

After establishment of the garden

 

20 t/ha         

30 t/ha/yr (in 2 equal split doses), after each base cut

Chemical Fertilizers :

During  establishment  of  the garden  (in 2 split doses)

100:50:50 kg  NPK/ha (in 2 equal split doses)
Annual : After  establishment   of the garden   

240:140:140 kg N PK/ha/yr

(in 4 equal split doses after each pruning)

Pruning: Annual basal cut at 30 cm above the ground, preferably during the onset of the monsoon. Following the 1st base cut and 3 leaf harvests, at an interval of 15 days, 1st middle pruning at 60 cm above the ground has to be done. Followed this, 3 leaf harvests can be made. Again, the same sequence may be followed. Totally 2 base cuts and 2 middle cuts done yearly. After about 20 days of each pruning, weak branches can be removed.

Irrigation: In light sandy loam soils, irrigation at 7-8 days interval may be necessary while in heavy clay loam soils, irrigation at 8-10 days interval may be found adequate. It has been estimated that 1.5 to 2 acre inches of water per irrigation is required. To save irrigation water micro irrigation system can be suitably adopted.

Leaf harvesting and preservation: The leaves to be harvested will be from below the largest glossy leaf which is yellowish green in color. The cardinal point is shoot tips should not be removed during any leaf harvest. From the glossy leaf, about 3 leaves during the 1st (1-3) and about 3 leaves (4-6) during 2nd instar can be harvested. Usually in cool hours (morning and evening) leaf harvest has to be done. The harvested chawki leaves should be preserved in cool and clean (hygienic) placers in order to preserve their succulence.

Plant protection:

Diseases: Powdery mildew, Leaf spot, Leaf rust, Stem canker, Root-rot and Nematode.

Pests: Thrips, Mites, Jassids, Tukra and Leaf roller. Generally for control of fungal diseases spraying of 0.2% Bavistin (Carbendazim) with 15 days safe period and for control of nematode infestation, soil application of Furadon 3G at 6-7 kg/0.4 ha with 45 days of safe period and for control of pests, spraying of 0.1% Metasystax can be employed. But, plant protection measures can be taken only after 2 base cuts and 2 middle cuts and 15-18 days before leaf harvest for brushing.

Advantages:

  • By the adoption of annual pruning schedule of 4 prunings and 12 leaf harvests, higher leaf yield of about 10,000 kg/0.4 ha/yr can be obtained and 60,000 dfls can be brushed/year, at the rate of 15 kg chawki mulberry leaf/100 dfls.
  • Increase in number of harvests and maintenance of vigor of the plants may suitably adjusted by adoption of yearly 4 prunings and 12 leaf harvests schedule.
  • This schedule can be easily practiced by private CRCs/large scale sericulturists.
  • Good quality chawki leaves for every harvest could be produced at an interval of 15 days. The leaves will be rich in leaf-water content and nutrients and when fed to young silkworms, their growth will be best.
  • If a chawki mulberry garden or a plot is divided into two plots/units and the recommended package of practices followed, yearly 24 chawki leaf harvests can be obtained to facilitate regular brushings once in 15 days at CRCs.
  • The advantage of this package is, other than obtaining suitable leaf for chawki rearing, chawki leaf can be produced throughout the year continuously coinciding with the brushing programmes.
  • Conducting late age silkworm rearings with good chawki reared worms will lead to good cocoon production.

Precautions:

  • Adequate irrigation and recommended inputs must be ensured.
  • The cardinal point is shoot tips should not be removed during any leaf harvest.
  • Plant protection measures can be taken only after 2 base cuts and 2 middle cuts and 15-18 days before leaf harvest for brushing.

Brushing of silkworm eggs:

  • At the time of brushing, the mulberry leaf is cut to fine ribbons and sprinkled over the hatched worms to facilitate easy transfer of larvae from the egg sheet to the bed.
  • After half an hour the worms are tapped on the rearing bed in the tray and 0.5 sq.cm cut tender leaves are fed.
  • The size of the bed for 25 dfls should be 25 sq.cm.

Methods of young age rearing: Different methods of young age rearing are in practice. The most common methods are box and stand rearing.

Box rearing:

  • Wooden trays of 4� x 3� x 2� and 4� depth are used.
  • Trays during feeding period are arranged one above the other upto a convenient height. It can increase the temperature/humidity in the rearing bed.
  • Keep the trays in criss-cross condition for 30 minutes before feeding to allow fresh air.
  • 30 minutes before feeding and during moulting period, the paraffin or polythene sheets are removed.
  • Minimum space is requirement.

Stand rearing: Stand rearing is done when optimum temperature and more rearing humidity are available in the rearing room. In this method more rearing space is needed.

Cover rearing method: During the first two instars, the rearing bed of young larvae is covered with polythene sheets both at the bottom and top with four sides wrapped. The size of plastic film is 116 cm x 86 cm (depends on the size of tray), thickness 0.03-0.4 mm. The polythene should be punched and the size of the hole should be 0.15-0.2 mm and distance between the holes should be 1.5-2 cm. The polythene sheet should be transparent.

Feeding/Nutrient requirement for chawki rearing:

  • Chawki worms should be fed with succulent mulberry leaves rich in nutrients and moisture content viz., water content (80%), protein (27%) and carbohydrates (11%).
  • Separate chawki garden with superior mulberry variety like KNG or lchinose are maintained by providing irrigation and inputs such as FYM and chemical fertilizers in the recommended dose (FYM : 40 MT; N:P:K:300:150:150)
  • Select first glossy leaf from the top of branch for 1st feeding at the time of brushing and with the advancement in larval age the first 3-4 tender leaves can be used.
  • Leaf harvest must be done in the morning and evening.
  • Preserve the mulberry leaves in a cool place covered with wet gunny cloth.
  • In dry season, sprinkle water over leaves and preserve them under wet gunny cloth.
  • Chopped leaves should be fed to worms for uniform growth.
  • Three feeding schedule viz., 6 am, 2 pm and 10 pm should be followed.
  • Stop feeding when above 90% worms settle for moult and resume when 95% worms comes out of moult.
  • 30 minutes before feeding, the paraffin or polythene are removed and after feeding the rearing beds are again covered with polythene sheets.
  • The size of the leaf fed should be 1.5 sq.cm. in first stage and increased to 3 sq.cm. as worms advance in age.
  • Size of the leaf should be reduced when worms start settling for moult.

Bed cleaning: Only two cleanings are recommended during second stage and no cleaning in first stage. Cleaning nets are applied on the bed, chopped leaf is fed to worms. Worms crawl through the net. After two hours, worms are transferred to another tray. If cleaning nets are not available, the topmost layer with worms must be taken with a feather.

Spacing: Overcrowding of the silkworms in the early stage leads to sizing and poor growth. Regulate the spacing for the healthy growth of the silkworms. There should be uniform distribution of the larvae in the bed.

Use of bed disinfectant: Dusting of bed disinfectants is important to avoid secondary contamination. The quantity of dusting of different bed disinfectants for 100 dfls is around 50g after 1st moult and 100g after 2nd moult.

Care during moult:

  • Ensure good aeration and dry conditions in rearing bed during moult.
  • Remove the polythene during moult period.
  • Temperature/humidity should be kept 1�C less viz., 26�C and RH 65-70%.

Concept of chawki rearing: To raise a healthy stock of silkworms the system of chawki rearing must be quite effective:

  • Maintenance of optimum temperature/relative humidity.
  • Feeding of nutritious tender leaves.
  • Maintenance of absolute hygienic conditions.
  • For rearing chawki worms experienced persons are needed.

Presently most of the farmers are engaged in self chawki rearing. However, cooperative chawki rearing have the following advantages over existing technology.

  • Ensuring uniform embryonic growth and good hatching.
  • Minimizing the missing larval resulting in higher larval population.
  • Robust and disease free growth of the worms.
  • Prevention of crop loss and stabilization of cocoon crop.
  • Minimization of pest and disease out break by synchronization of crops
  • Crop monitoring is easier and effective
  • Effective utilization of saved labour and time for other activities.
  • Higher cocoon yield of good quality at reduced production cost.
  • By adopting the chawki rearing technology, farmers get 5-6 kg more cocoon yield compared to doing self chawki rearing. In addition to cocoon yield, farmer will be free from rearing activities for about 10 Days. Cocoon production cost reduced and crops will be synchronized.
  • The technology develops co-operations among farmers. This has social impact on villagers. CRCs are back bone of sericulture industry and all the important technologies can be advocated through CRCs. Marketing of cocoons can also be linked through CRCs.

Distribution of chawki worms: Worms in the tray can be rolled along with punched paraffin/old news paper at the base and top. Ends are closed and stapled. Worms should be transported to the rearers house during morning hours and fed immediately with fresh leaves.

Precautionary measures during the rearing of young larvae:

  • Before entering the rearing room, where chawki worms are reared, hands should be washed.
  • Separate footwear should be used inside the rearing rooms.
  • Silkworm litter should not be thrown in the rearing room.
  • Rearing rooms should be kept clean and tidy.
  • Avoid touching the worms.

Standard Chart for young age silkworm rearing (100Dfls larvae)

Larval Stage Age (days) Feeding time

Leaf size in

Sq. Cms

Bed area

(Sqft)

Leaf quantity Remarks

 

 

I

Instar

27-28OC

80-85% RH

 

1

10 A.M

2 P.M

10 P.M

Finely chopped

0.5 x 0.5

0.5 x 0.5

 

4-7.5

 

500 gm Expose layings from black box to light around 7AM. Brush the larvae. Brush the larvae around 9 AMusing finely chopped tender fresh leaves. Make the bed after about 30 minutes, give feeding with cut leaf of 0.5x 0.5

 

2

6 P.M

2 P.M

10 P.M

1.0 x 1.0

1.5 x 1.5

1.5 x 1.5

 

7.5-10.5

 

1,800 Spread the bed half an hour before feeding for drying.

 

3

6 A.M

2 P.M

10 P.M

1.5 x 1.5

1.5 x 1.5

0.5 x 0.5

10.5-15 1,200 Spread the bed half an hour before feeding for drying. Observe for moulting behaviour, reduce the leaf size and quantity appropriately

 

I

moult

 

4

6 A.M

2 P.M

10 P.M

0.5 x 0.5

1.5 x 1.5

1.5 x 1.5

15 200 Stop feeding when about 90% of larvae settle for moult. Break/ Spread the bed gently and apply fresh active lime powder @4-5g/sqft to dry the bed.

 

 

 

II Instar

27-28OC

80-85% RH

 

5

6 A.M

2 P.M

10 P.M

1.5 x 1.5

1.5 x 1.5

2 x 2

15-30 3,500 Give feeding if more than 90% of the larvae are out of moult. Disinfect the larvae/bed before feeding. Clean the bed using net.

 

6

6 A.M

2 P.M

10 P.M

2 x 2

2 x 2

2 x 2

30-45 4,250 Spread the bed half an hour before feeding for drying.
7

6 A.M

2 P.M

2x 2

1x1

45 1,100 Observe for moulting behaviour, if the symptom of moulting is observed reduce the leaf size and quantity, clean the bed before settling for moult.
II moult

 

 

8

10 P.M

6 A.M

10 A.M

2 x 2

-

45 - Stop feeding when about 90% of larvae settle for moult. Spread the bed gently and apply fresh active lime powder.

Isolation Chamber:

Young age rearing is the most important activity in silkworm rearing. A good chawki is the key for a successful crop. However, most of the farmers do not have a separate chawki rearing room.

Realizing the prevailing situation, an isolation chamber has been evolved which helps in providing all the required conditions to a large extent in the farmers rearing houses and chawki rearing centres. It is observed that when chawki is raised in such isolation chambers there is an increased larval and cocoon weight with better survival rate and therefore higher yields.

The isolation chamber can easily satisfy the average farmer as it can easily be accommodated inside his dwelling house. The isolation chamber can be made either with wood or brick masonary. Construction details of a model isolation chamber for a unit of 300 dfls upto 2nd moult is as follows:

The isolation chamber can easily satisfy the average farmer as it can easily be accommodated inside his dwelling house. The isolation chamber can be made either with wood or brick masonary. Construction details of a model isolation chamber for a unit of 300 dfls upto 2nd moult is as follows:

Height : 6�
Width : 4�
Depth : 5�

Door: Single door of 5.5� x 4� with a glass window of 6� x 9� in the centre of the door, at a height of 4.5� to 5� from the floor for installation of wet and dry bulb thermometer from inside the chamber.

Ventilators: Lower two rectangular ventilators of 4 x 9 size. Two circular ventilators of 7 dia size in the roof of the chamber with sliding doors and uzi proof mesh fixed.

Heating facility: To increase the temperature, a 2 KV blowing type heat convector can be fitted to one of the ventilator in the bottom of the chamber. The heat convector is connected to a thermostat to regulate the temperature.
Humidity of the chamber is increased by keeping water in wide tray on the floor of the chamber in addition to the use of wet foam pads around the beds, if necessary.

Rearing stand: Rearing stand of 5.5� height, 2.5� width with 14 tiers with a distance of 4.5� between each tier.

Rearing tray: Standard wooden chawki tray (box) of 3� x 4� x 2.5� size, 14 trays are required per chamber. The bottom and top most trays will serve as dummy trays leaving 12 trays for rearing 300 dfls at the rate of 25 dfls per tray. If the rearing capacity is more, chambers can be constructed side by side.

Temperature and humidity inside the chamber: Maintenance of uniform temperature and humidity is easy inside the chamber, mainly because of the restricted area. When heater is used to increase the temperature, the power consumption is very less as the heater is on, only for few hours per day as compared to continuous functioning outside the chamber. Further, under non-manipulated conditions (when heater is not used) the temperature is uniform without much fluctuation inside the chamber, which is more congenial for the growth of the larvae as compared to wide fluctuations outside.
It is observed that humidity is always on the higher and uniform in the chamber as compared to outside.

Maintenance of leaf quality: The loss of moisture of cut leaves used for chawki rearing is very less inside the isolation chamber mainly because of prevailing high humidity. As a result of this the bed life of leaf is better which enhance the leaf utilization efficiency as reflected by the increased chawki larval weight.

Ventilation management: Proper aeration inside the chamber is achieved through lower and upper ventilators. One of the lower ventilators is closed when the other is fitted with blowing type heater, while the upper ventilators are to be keep open by � of its size during the beginning of the first instar. As the larvae grow, gradually, upper ventilators are opened to � of its size by the end of the second instar. Keep both the lower ventilators open when the heater is not used. All ventilators should be fully opened, half an hour before feeding to facilitate the bed drying, so also during moulting to reduce humidity and to keep the bed dry. Unnecessary opening the doors should be avoided since it affects the uniform maintenance of temperature and humidity and also increases the chances of contamination of dust and pathogens.

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