SILKWORM DIVISION

A. FAQ’s - Silkworm Breeding and Genetics

B. FAQ’s - Silkworm Pathology Section

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A. FAQ’s - Silkworm Breeding and Genetics

1. How many silkworm races are present in the world?

More than 4400 races are present in the world. These races are mainly reared in

China, Japan, Russia, India, Korea, Bulgaria, Brazil etc.,

2. How the silkworm races are classified?

Silkworm races are classified based on number of generation in a year, moults,

cocoon shape, size, geographical region and the larval markings.

3. What are univoltine, bivoltine and polyvoltine races? Is it possible to identify

based on the egg colour?

Based on the number generation in a year silkworm races are classified. Univoltine

race completes only one generation in a year. But the bivoltine races complete two

generation in year and polyvoltine races completes 6 to 7 generation in year.

Generally, Univoltine and Bivoltine eggs are light yellow in colour when they laid

and gradually turn into brown in colour after 1-2 day after egg layings. The eggs

laid by the moths of polyvoltine are deep yellow in colour and maintains the same

even after 1 to 2 days. An exception to this, in some polyvoltine races like

Madagaskar/Vietnam and also KS-10 the eggs laid turn brown like bivoltine and

development of embryo continues like polyvoltine.

4. How the silkworm races are classified based on the moult?

Based on the moult the silkworm races are classified into Trimoulter, Tetramoulter

and pentamoulter

Trimoulter : Moults three times in its larval stage

Tetramoulter : Moults four times in its larval period

Pentamoulter : Moults five times in its larval period

5. Will the silkworm larvae have larval marking? If they are present how are

they?

Silkworms have different larval markings. Based on the larval marking larvae are

classified into plain and marked. Marking like ECS, Zebra, Multilunar, black are

found on the larvae.

6. How many cocoon colors are found ?

There are different types of cocoon colors, namely, yellow (polyvoltine), Yellow

(Polyvoltine), violet (Univoltine), white (Univoltine and bivoltine)

7. How many different shaped cocoons are found in silkworm races?

Different shaped cocoons are present in the silkworm races.

Oval shaped cocoons : Generally, It is found in the races of China

Dumbell shaped cocoons : Generally found in Japanese races

Spindle shaped cocoons : Tropical races spins spindle shaped cocoons

8. What are European races?

European races are generally Univoltine or Bivoltine. The races spins yellow or

white coloured dumbell shaped cocoons.

9. What are Chinese races?

Chinese races are generally univoltines or bivoltines and spins white cocoons. The

main characteristic is the spinning oval shaped cocoons.

10. What are Japanese races?

Japanese races are generally univoltines or bivoltines and spins dumbell shaped

white cocoons.

11. What are tropical races?

In Asian countries like Bangladesh, India and south east countries polyvoltine

races are present spinning yellowish spindle shaped cocoons.

12. Have Japanese developed seasonal races suiting to different seasons? If

developed, what are they?

Japanese have developed different races suiting to different seasons

For Spring season Thahei X Chohan, Hukuba X Thenrai, N122 XC122, Shungei

X Hosho, J uyeko X Chimpaku, N124 X C122, Shanrai X shogethstu and Asahi X

Shokaei

Similarly for summer season, N122 X C108, Choko X Shinva, Shoko X Ginrai

N122 X C155 Kinshu X Shono, N124 X C124, Guyo X Thokai

13. What are the races of Russia?

Univoltine and bivoltine races are used in Russia. Shanishi, Ajan baiko,

Belkokonai races are used

14. Has China developed different races suitable to different seasons? If so, what

are they?

China has developed more than 43 hybrids. These hybrids are authorized and

recommended for farmers use.

Chunle X Minsu, Jingshang X Hauvoyuve, Jeyli X Jun shiyaho, Shuhuva X

chihuyi, Yangvang X Chuyu

ChuvangkanX11, 671 X 872, Hvafeng X shuye hybrids are reared in spring

During summer, kyupang X Jahushiya, Shi hang X keming, Shahuva X Kyushin,

Shiyalei X Minkyu hybrids are used

For all seasons, Shuvangkan X 11, 871 X 872, Hvapeng X Shuye hybrids are used

15. What are the indigenous silkworm races in india? What are their special

characters?

In India, indigenous silkworm races includes univoltine, bivoltine and

multivoltine races. Borapolu and Kashmir Breed are univoltines. Jam is the

bivoltine. Nistari, Chotopolu, Pure Mysore, Balupolu, Nayapolu, Surupath, Moriya

white, HS6 are polyvoltines. These races have the special character of adjusting

itself to local climatic condition and high resistance. The silk content is very less.

16. What are the different races developed in India during the year between

1970 and1980?

Suiting to local agro climatic conditions, central and state research institution have

developed many polyvoltine and bivoltine races. Some of the bivoltine races

developed are KA, NB7, NB18, NB4D2, CA2, CC1, JA2, PCS and SH6

Similarly, Nismo, Ichot, Itan, Kolar Gold, Mysore Prince, Kollegala

Jawan,Tamilnadu white, Hosa Mysore, MY1, MY2, P2D1 etc., are the polyvoltine

races.

17. What are the bivoltine and polyvoltine race developed in India after 1990 and

what are the special characters of them?

Many races have been developed by state and central research institutes. The

important bivoltine races are Jam, MG, MU, APS5, APS8, NP2, SP2, KSO-1,

NTCM, CN2, WU8, CSR2, CSR4,CSR18 and CSR19. Similarly, MH1, BL23,

BL24, BL67 , APM1, MCon1, MCon4 and C110 polyvoltine were also

developed. These races have good resistance and more silk content

18. What are sex-limited races?

By adopting silkworm breeding technique, the sex limited races were developed.

With this technique, male and female were separated easily in egg, larva and

cocoon stage. In Japan, china, Russia , sex limited races were developed for the

farmers use.

19. Has India developed sex-limited races?

Yes. Research institutes of Central Silk Board and different state research institute

have developed sex limited races in 1980s. Some of the sex limited bivoltine races

are CC1(SL), NB4D2(SL), CSR18, CSR19 etc., Similarly polyvoltine sex limited

races were also developed. They are PMX, Nistari (SL)

D18B (SL), MBD IV( SL,)AP1(SL) etc., In these races, larvae of male are plain

and female are marked.

20. Has Karnataka State Sericulture Research and Development (KSSRDI)

developed sex limited races?

Silkworm Breeding Unit at Bidadi in Karnataka State Sericulture Research and

Development has developed sex limited races

Bivoltine : HND, HD(O),KSD-8,Wu-8 etc.,

Polyvoltine : SLKSPM

Based on the larval markings, male and female larvae are identified. Males are

plain and female are marked.

21. Generally, in tropical belt, polyvoltine races spins coloured cocoons. But what

is the character of a white cocoon spinning race developed in KSSRDI?

In coloured cocoon spinning races the gummy substance is more. Because of this

the reeling parameters are not good during rainy season. The raw silk neatness

and strength of the filament is less. The KSSRDI has developed polyvoltine

MH1,which spins white coloured cocoons, to overcome these defects. The cross

breed using MHI, MHIXCSR2 hybrid is successful in exhibited good yield and

good quality silk in Karnataka, Andrapradesh, Tamilnadu, Orissa, Uttarpradesh

and Assam states. This hybrid is authorized for commercial exploitation by Central

Silk Board, Government of India

22. What is Bangalore Belli ?

To overcome the minor defect in the reeling, fine tuning MH1 is done by adopting

line breeding in KSSRDI. Subsequently this improved breed (IMH) is used for

cross breed preparation IMHXCSR2, which is called as” Bangalore belli”. This

can be reared in all the seasons. This hybrid is reared in Kolar, Mandya and other

parts of Karnataka

23.What is double hybrid?

In double hybrid, two foundation crosses are used. The central research institute

has developed the hybrid (FC1X FC2). About 90% of the bivoltine silk is

produced from this hybrid. This hybrid has four parents, namely, CSR2, CSR27,

CSR6 and CSR26.

23. What are “Adithya” and “Kasturi”?

Karnataka State Sericulture Research and Development Institute has identified two

bivoltine double hybrids, viz., Adithya and Kasturi during the year 2018. Adithya

can be reared all the season. This hybrid is used as an alternate to the existing

double hybrid. This hybrid has good resistance and egg recovery over the existing

double hybrid .This hybrid has four parents CSR6, CSR26, BRO-2 and NK2. The

other double hybrid identified only for favorable season is Kasturi. This has four

parents CSR2, CSR27 and ASP46 and K9D. These hybrids were reared with the

farmers in different parts of Karnataka viz., Ramanagara, Kolar, Mandya

Kanakapura, Gulburga

24. What is Germplasm bank ?

More than 4400 silkworm races are present in the world. In order to maintain

these races with their basic characteristics the germplasm banks are established.

Here the races were collected, conserved and classified on their basic characters of

the races. The promising races are used in the development of breeds. The

germplasm is maintained at CSGRC, Hosur, under the control of central silk,

India. Similarly, Germplasm races are also maintained at Silkworm Breeding and

Genetic Section KSSRDI, Thalaghattapura, Bidadi and substation Ooty.

25. Explain the races developed by Karnataka state sericulture research and

development institute for summer.

The bivoltine hybrid Rajathasampathu NP2XKSO-1 was popularized in the field

during summer in four districts of Karnataka under Seri-2000. In order to improve

the productivity, one more BR-2X NP4 hybrid was developed and recommended

for summer. These hybrids have many advantages like resistance against the

diseases, less amount of leftover leaf in the bed, tolerant to high temperature, more

leaf to silk conversion efficiency, easily to identify the rape worm and less number

of meltage cocoons. BRO-2XNP2 hybrid was popularized in Ramanagara,

Bangalore (Urban), Kolar, Mandya districts during from 2006 to 2008. The

farmers have harvested cocoon yield of 58 kg/ 100 dfls and fetched Rs. 20/- per kg

of cocoon more compare to cross breed.

26. Give details about the productive bivoltine hybrid developed in Karnataka

State Sericulture Research and Development Institute.

Under Seri-2000 project, six new productive bivoltines were developed. Using

these bivoltines the productive bivoltine hybrid NK-2X HND and HNDXNK-2

was developed. This hybrid has good productivity and recommended for rainy and

winter season. This hybrid has high shell content of 22 to 23%. After laboratory

studies, these hybrids were field tested in Ramanagara, Mandya and Kolar

districts. The farmers have harvested cocoon yield of 60 kg per 100 Dfls. Compare

to CSR-2XCSR-4, the yield is on par with the CSR-2XCSR-4. But the rate of the

cocoon per kg was Rs.20-25 more than the cross breed. The farmers are happy

with crop due to disease resistance. The silk produce has good yarn

characteristics and the quality is on par with the international standard.

27 Name authorized hybrids developed by Karnataka State Sericulture

Research and Development Institute.

Five races developed by Karnataka State Sericulture Research and Development

Institute are authorized by Central silk board, Government of India, They are

1. Bivoltine hybrids : KSO-1 X SP2

: KSO-1 X NP4

: NK-2 X NP4

2. Cross Breed : MH1 X CSR2

3. Polyvoltine : PM X C100

28. Give information about the other cross breeds developed by Karnataka State

Sericulture Research and Development Institute.

After observing the limitation in the multiplication of CSR-2 race for using it as

male parent with the cross breed PMXCSR-2, favorable productive male parent

NK-2 was developed. Experiments were conducted by using NK-2 male with PM

female, (PMXNK-2). Nk-2 used was found resistant to disease and helpful in

giving more number of males for crossing purpose and found economical for

graineur. For one kg of cocoon the NK-2 can give 230 active males for crossing.

This new cross breed PMXNk-2 was popularized in Bangalore (Urban),

Ramanagara, Kolar and Mandya. The rate of the cocoons and cocoon yield

produced from the cross PMXNK-2 are on par with PMX CSR-2. This hybrid

found successful in farmer level. NK-2 is recommended as an alternate male

parent in the in the cross breed PMX CSR-2 in the grainage.

29. What is race authorization?

Race Authorization is a process of evaluating the developed races for commercial

multiplication in a systematic way .This system is in vogue in Japan, China, Russia

and other countries .It is also common for the scientists of forest /Agriculture

department to submit the application for authorization.

30. Is India having race authorization system?

Yes. This system came into existence in India from 1994. Applications will be

submitted to the Central Silk Board, Government of India by the scientist who

developed new hybrids for race authorization. The race authorization committee

conducts multi-locational trails of newly developed hybrids in 20 different places.

The data will be collected, analyzed and the promising hybrid will be

recommended by the race authorization committee. In India there are about 29

bivoltine hybrids, 20 crossbreed and five polyvoltine races were authorized.

31. Has our state developed seasonal breeds of bivoltines ?

During 1990 the central sericultural research institute, Mysore, Karnataka state

sericulture research institute, Bangalore and Andrapradesh Sericulture Research

Institute, Hindupur have developed season specific races.

32. What are the bivoltine hybrids specific to summer season ?

CSR18 x CSR19 developed by the central sericultural research institute, Mysore,

and KSO1 x SP2, KSO1 x NP2 and BRO2 x NP4 developed by KSSRDI are used

as bivoltine races for summer season. These races are tolerant to high temperature

and low humidity. These races have medium yield and higher resistance to

diseases.

33. What are the bivoltine hybrids recommended for rainy and winter ?

CSR2 x CSR4,CSR2 x CSR5, CSR3 x CSR6 , CSR46 x CSR47 developed by the

central sericultural research institute, Mysore and NK2 x HND,NK2 x NP4 are

developed by KSSRDI are used for rainy and winter season. The other research

institute APSSRDI, HIndupur has developed APS5 x APS4, APS105 x APS126,

APS45 x APS12 for rainy and winter. These hybrids have good cocoon yield and

silk content.

34. Name the races with special characteristics?

There are many races for special character developed around the world. Some of

the special characters are

1. High disease resistant

2. High temperature tolerant

3. High silk content/Thin denier

4. Low sericin content

5. Silk size deviation

6. Silk neatness

7. Less floss

8. Sex-limited

9. Artificial diet

10. Anti diapause

B. FAQ’s - Silkworm Pathology Section

1. Diseases of silkworm can be classified into four main types based on

the causative organism. Microsporidia - Pebrine disease

Virus - Grasseri, White Flacherie, Kenchu

Bacteria- Flacherie, Sotto

Fungus - White / Green muscardine, Aspergillosis.

Flacherie Disease and Control:

2. What are the specific symptoms of bacterial flacheire disease and

methods to diagnose the disease?

The flacherie diseased larval body become soft, skin loosens,

vomiting and diarrhea.

The larval skin gets bleached and there is unevenness in growth.

Worms are inactive, do not wish to feed, the body blackens and later

decompose.

3. What are the main reasons for the cause of flacherie? Lack of proper temperature and humidity during silkworm egg

incubation.

Improper collection and disposal of dead and diseased larvae and

other bed waste leads to secondary contamination.

Improper rearing practices, bed thickness, starvation, poor quality

leaf, inadequate quantity and drying of leaf leads to starvation.

High larval density (Over crowding of larvae) in the rearing bed, lack

of good temperature and humidity.

Feeding poor quality leaf- dry, mature, or dusty leaf.

4. When does the flacherie disease occur? Although the disease is common throughout the year, it is more

frequent during the summer especially during hot and humid weather.

During premonsoon when there is fluctuation in weather condition.

Unhygenic rearing conditions.

5. Name the pathogen that causes flacherie disease. Flacherie is caused by different types of bacteria that belong to the species

Streptococcus, staphyllococcus, Bacillus.

6. Is there any correlation between variation in the temperature and

incidence of flacherie disease?

Pathogenic bacteria multiply rapidly when the temperature rises

above 280C in the silkworm bed. During rainy and cloudy weather,

the temperature fluctuates, causing flacherie disease.

7. Why do the larvae blacken and die on the chandrike?

As the bacteria develop in the worm's body, the disease develops in

the digestive tract, leading to nutritional deficiency, which changes

their physiological functions and decreases the acidity in the digestive

tract.The larvae then vomits a brown liquid, turns brown and the body

quickly decomposes and emits a foul smell. The symptoms are

commonly seen during the adult larval stage or during spinning. This

symptom is known as gastrointestinal disease.

8. Is flacherie disease caused due to defective eggs? Flacherie disease caused by bacteria is noticed when poor quality leaf

is fed to silkworms. This disease is not tranferred from eggs to the

progeny. But silkworms become infected more quickly by various

unscientific methods of silkworm rearing.

9. Does feeding of wet leaf cause flacherie disease and if so, how to

control it? Feeding wet leaf during silkworm rearing increases the moisture in

the bed hence bacterial count increases in the silkworm body.

However, partial air drying of the leaf before feeding and proper bed

disinfection using recommended bed disinfectants and lime controls

flacherie disease.

10. Does flacherie disease occur if tender and mature leaf is mixed and

fed to silkworms? In the tray rearing method it is customary to feed the leaf based on the age

of the larva. Hence, feeding mixture of tender and coarse leaf causes

flacherie disease. However, in the shoot rearing method feeding of mixed

quality leaf is done from the early instars. So the incidence of disease is

minimal. It also depends on the cleanliness of the bed.

11. What are the measures to control flacherie disease?

Conduct general disinfection and bed disinfection as recommended.

During rearing provide the right temperature and humidity depending

on the age of the larva.

Provide good circulation of air during rearing especially to adult

worms.

Provide good quality leaf based on the age of the silkworms.

Store the leaf properly covered in a wet cotton cloth and reduce leaf

moisture evaporation during storage.

Provide nutritious leaf to the silkwoms. Soiled and ripened leaf

should not be used.

During the course of rearing, collect under sized, diseased and dead

worms from the rearing bed and dispose them in scientific manner.

12. Why do we notice flacherie normally during V instar? Though infection occurs in the early stages, there is ample time for

the pathogen number to increase and the symptoms appear in the V

instar. At this stage there are biochemical changes for silk production,

there are considerable changes in the gastrointestinal tract also.

13. What are the precautionary measures to manage flacherie disease? Effective disinfection of rearing house and appliances atleast 2-3

times per rearing.

Egg incubation as per recommendation for proper embryo

development.

Use of bed disinfectants as per recommendation.

Collection and disposal of diseased and dead worms during rearing.

Provide good air circulation, temperature and humidilty as per the age

of the larva.

Maintaine the health of the bed.

Provide nutritious leaf.

14. Are there any measures to control flacherie disease after its onset? Generally, flacherie disease control measures are precautionary

measures. Once infected, the spread of the disease can only be

reduced.

15. How to dispose the sick or dead silkworms? Daily before feeding, collect diseased or dead silkworms from the

rearing bed and dispose in lime water / bleaching powder solution/

chlorofect/ Shuchi or any disinfectant solution. Later bury or burn

them. This reduces the severity and spread of the disease in the bed

due to secondary contamination.

16. What is the definitive drug for the control of flacherie Disease?

There are no curative methods to control flacherie disease. Diseases

are manged by preventive methods like rearing house disinfection,

bed disinfection, maintaining hygine during rearing.

17. Do bacteria spread through the eggs?

Bacterial flacherie does not come through the eggs.

18. What are the symptoms of Thatte disease?

It is a symptom of healthy grown 5th stage larvae suddenly stop

feeding and move underneath the bed and begin to die.

19. Does thatte disease occur in specific tray or stand? No, during V instar larvae die in any place, on any rearing tray. This

symptom is unrelated to the location of the tray and rearing stand.

20. What causes Thatte disease?

For adult silkworms, fresh air is essential, if the circulation of air is

poor and the larval density is high, due to respiratory problem the

worms go inside the bed and die in a couple of days. Later secondary

infection of bacteria occurs.

21. How to control thatte disease?

Under the tray system of rearing thatte disease is commonly noticed.

Switching from tray method to shoot rearing method reduces thatte

disease.

Installing ventilators/ smoke pipes in the rearing room increases air

circulation and reduces thatte disease.

If lime is dusted on the worms and trays are displaced, the silkworms

will survive.

22. What is the difference between thatte disease and Flacherie? Flacherie diseased worms are reduced in size and the worms die

slowly and not restricted to V instar. Dead worms become either

black or reddish.

Thatte diseased worms are uniform in size and healthy. The worms

stop feeding in 5-6hrs and die in 1-2 days. Normally observed during

V instar.

Grasserie disease

1. Tell us about Grasserie disease in detail?

Grassserie is caused by Bombyx mori Nuclear polyhedrosis virus (Bm

NPV). It is common during summer and rainy season.

The root cause of the disease is high temperature and low humidity,

weather fluctuation during larval growth, poor quality leaf and

secondary contamination. Although during the initial stages of

infection the larvae appear healthy and in the final stage the larval

skin appears shiny, rupture easily, inter-segment swollen, and move

around recklessly releasing the thick white blood containing

numerous viral polyhedra.

To control the disease, proper disinfection of the rearing house and

equipment. Proper destruction of diseased worms, provide good

quality mulberry leaf, proper ventilation, bed space and maintenance

of hygiene. Disinfection as recommended and use of bed

disinfectants. When polyhedra come in contact with lime water, the

outer polyhedral coat ruptures and loses its pathogenic potential. So

lime should be used extensively.

2. For about 4-5 years without using any disinfectant I was getting good

cocoon yield. But since one year I have lost crop due to grasserie and

flacherie. Why? Silk grower takes 5-6 crops a year. In each crop, disease causing

pathogens are released from dead worms and spread in the rearing room,

rearing appliances and in the environment. This causes an increase in the

number of pathogens in the environment. The worms die in small number

in the intial stages, as the pathogen load increases in the rearing

environment crop loss is high and reach a stage where the entire crop is

lost. To prevent this, it is necessary to disinfect the room and appliances

twice for each crop, i.e. before and after every rearing. Chlorine based

disinfectants control grasserie disease effectively.

Kenchu Disease and Control:

1. In which season is kenchu disease most common?

Kenchu is a disease caused by Densonucleosis Virus (DNV). This is

most commonly seen in rainy season from May to September due to

high temperature and humidity in the atmosphere.

2. At which stage does kenchu disease occur?

Kenchu is most commonly noticed in the chawki stage. The virus is

highly contagious and can spread in a favourable environment in the

larval population. It takes 8-10 days for the symptoms to appear.

3. It is difficult to achieve good cocoon yield once the Kenchu disease is

noticed. So what are the preventive measures to control the disease? DNV is highly infectious and the pathogen can remain alive in the rearing

environment and appliances for more than 6 months. The dust in the rearing

house, rearing equipment is the main sources of contamination. Therefore, it is

important to disinfect the rearing house and appliances by scientific methods.

Disinfection should be conducted 2 times i.e. after completion of each rearing

and start of the next rearing. Bed disinfectant should be used in the

recommended dose during the course of rearing. Hygiene of the rearing house

and surroundings should be maintined by cleaning and use of Shuchi or any

other room disinfectant. If diseased/unequlal silkworms are detected, they

should be collected in a basin containing lime water or any other disinfectant

solution and then burnt / or buried in a manure pit. Replace the contaminated

rearing tray and dust bed disinfectant onto the tray and then transfer the worms.

Dust recommended bed disinfectants like Sanjeevini / Samrakshak and then feed

the silkworms. Dust bed disinfectant on alternate days to avoid secondary spread

of kenchu disease. Used equipment should be disinfected and kept in direct

sunlight for 8-10 hours as the viruse loses its viability rapidly in sunlight. To

maintain hygiene in the rearing, regular cleaning of the floor should be done

using Shuchi (1: 100 dilution) and it can be used to clean the hands and feet of

the rearer.

Muscardine Disease:

1. Which is the pathogen that causes Muscardine and how does it cause

the disease? Muscardine is a fungal disease and there are two main types of fungal

disease: Muscardine and Aspergillosis. The conidia of this disease,

unlike other diseases, enter the body through the skin and not throught

the mouth/food.

2. Muscardine disease was commonly seen in Kolar recently where the

dead muscardine larvae are white initially and later turn green.

Why? The most common white muscardine disease is caused by the fungus

Beauveria bassiana, but more recently green muscardine is caused by

the fungus Metharrizium anisopliae, Spicaria prassina is also noticed.

The worms die when the conidia of muscardine disease germinate and

enter the body of the silkworm in a favourable environment, absorbing

all the nutrients from the silkworm body. The dead worms are soft

initially. The mycilia that comes out develops fruiting bodies and

produce conidia on the body surface giving white or green colour to

the mummified silkworm. The fungus infects all stages of the

silkworm like larva, pupa and moth. The duration required from the

time of infection to death/mummification is 2-3 days in chawki stage,

4-5 days in 4th instar, while it is 5-7 days for 5th instar.

3. Tell us about the pathogen causing white muscardine disease?

Muscardine is a fungal disease which can be identified as white, green,

red and black depending on the color of conidia on the body of dead

worms. In India, white and green muscardine is reported. The conidia

of B bassiana are circular in shape and looks like pebrine spore but

lack movement and luster that is specific to pebrine spore. The condial

spores enter the body of silkworm through the skin.

4. What are the main sources of fungal spores and how do they spread? In silkworm fungal pathogens causing Muscardine and Aspergillosis

disease comes out of the body of dead silkworm and spread through

the air in the rearing environment. So first of all the dead larvae are the

sources of pathogen. Disease spreads via the hands and legs of the

rearer, rearing appliances, rearing environment and pests of mulberry.

5. Which are the other fungus that cause Muscardine disease?

Usually on the body of of dead worms whitish dusty powder of the

pathogen Beauveria bassiana is seen. White muscardine disease

caused by Aphanocladium album and the fungi of the Acromonium

species is also reported. But these pathogens cause black spots when

they come in contact with the silkworm body and then the dead worm

turns white and mycelia is soft as cotton.

6. At what stage of the worm is the most common disease? During monsoon and winter season, when the temperature is low and

humidity is favourable, the disease is found at all stages of the larva.

The duration required from the time of infection to

death/mummification is 2-3 days in chawki stage, 4-5 days in 4th

instar, while it is 5-7 days for 5th instar and if infected in 5th instar

larvae spin cocoons but infection can be seen during pupal or moth

stage.

Aspergillosis:

1. Which are the pathogens that cause Aspergillosis? At what stage and

under what condition is this disease noticed?

Aspergillosis is a fungal disease and in Karnataka two species of

Aspergillus i.e. Aspergillus flavus and Aspergillus tamari infect

silkworm. Aspergillus is highly contagious and can grow on any

organic matter. The disease is more common in the chawki stage

because it requires high temperatures (27-280C) and high humidity

(80-90%) for its growth.

2. What are the symptoms of Aspergillosis disease and how does it cause

the disease? The conidia of the Aspergillus sps., enter the body through the skin in

a favourable environment, absorb the nutrients and produce a toxin

and this causes the death of worms. Mycelial growth is observed after

death of larva and dead larvae develops brownish green colour. The

duration required from the time of infection to death/mummification is

3-4 days. The dead larvae remain inside the bed. Due to the colour and

reduced size of the larva it is difficult to identify Aspergillus infected

chawki silkworms in the rearing bed. Adult silkworms show resistance

to this disease.

3. Integrated Control of Fungal Diseases? Disinfection is the most important factor in the prevention of fungal

diseases as dead worms on the trays are the source of infection.

Rearing house and appliances should be disinfected scientifically by

using 2% bleaching powder / Chlorofect / Sanitall plus/Seriphene

disinfectant before and after rearing.

During rearing, disinfectants bed disinfectants such as Suraksha/

Samrakshak/ Suraksha green should be used as a precautionary

measure from the chawki stage.

Many precautions must be adopted during rearing. They are: When the

eggs turns blue, the sheets of eggs are incubated in 1% formalin

solution for 5 minutes air dried in the shade. This prevents infection

through the egg shell.

During monsoon and winter season, the leaf do not dry quickly, so the

worms need to be fed with leaf as per the requirement and the bed

should be kept thin.

Lime should be used extensively when the larvae settle for moult this

reduces moisture in the bed and restricts germination of the fungus.

Enable good ventilation and light, do not cover the windows or cover

blanket.

Dead and unequal larvae should be collected and disposed

scientifically. Do not throw them openly.

Raise the temperature of the rearing house using an electric or

charcoal heater.

Transfer worms to disinfected tray to avoid secondary contamination

during rearing.

Pebrine Disease and Prevention:

1. Tell us in detail about Pebrine disease? Pebrine disease is casued by a microsporidian Nosema bombycis. The

disease spreads by two ways. a) From diseased mother moth to eggs

(primary source). b) by feeding spore contaminated leaf (Secondary

contamination)

The disease is most commonly seen in the monsoon and winter

months.

The symptoms of the disease are: The diseased moths lay clumped

eggs and the eggs do not stick to the paper. The wings of diseased

moths become curled and the scales fall off easily and appear

wounded. Larvae are irregular in size and are irregular to settle for

moult.

If the disease is caused by the primary source i.e. through the mother

moth then the pathogen load is high and the worms die in the first two

larval stages. The reason is that once the spore has entered. If

infection is in the IV or V instar, these infected larvae spin the

cocoons and become infected moths. To contain the spread of the

disease to the next crop mother moth examination is conducted in

grainages and disease free layings are distributed to farmers. To

prevent secondary contamination, rearing house and appliances are

disinfected. Since the pebrine spore infects the pests of mulberry, pest

free mulberry garden is maintained.

2. Why is mother moth examination conducted only to control pebrine

disease?

Pebrin disease spreads in two ways. From diseased mother moth to eggs

and by feeding spore contaminated leaf. If the disease is transferred from

the mother moth the embryo is infected. So to control the disease mother

moth examination is conducted in grainages. If spores are detected, such

eggs are burnt. Other diseases, such as Grasserie and Flacherie spread

during rearing and this can be prevented by dusting bed dinfectants and

maintaining hygiene.

3. Silkworms are healthy but do not settle for moult uniformly? The larvae show irregular settling for moult when they are infected with

pebrine. Microscopic examination of the unequal larvae or the faecal

matter should be conducted to identify the pebrine disease. Irregular

settling of the larvae for moult is noticed when there is scarcity of leaf in

the bed. The early feeders develop quickly and settle for moult and others

lag behind. It worsens in each stage and eventually worms show flacherie

symptoms in the 5th stage.

4. Is there any possiblity to misinterpret pebrine spores with fungal

spores during microscopic examination?

First let's know about the spread of silkworm and pebrine disease. In

silkworm, the fungal conidia, which is responsible for the cause of

disease in silkworm, comes into contact with the skin, germinates and

enters into the body and the hyphae are in the shape of a small-stick,

this further multiplies and the water content reduces and the worm

die, becomes harder. Aftr 24 hrs condiospores are formed and conidia

powdery like substance appear. When the powdery substances on the

dead worms are examined microscopically, conidia resembling

pebrine spores can be seen. However, it is not essential to test under

the microscope for the infection as muscardine disease can be seen by

its external symptoms. In addition, there is variation in the shape of

the two spores. The conidia of the green muscardine spores are oval,

tapered, and the white muscardine conidia are circular. However,

pebrin spores are oval, lustrous and have a brownian movement.

4. The main problem during microscopic exmination is that the images

appear dull or the light does not pass and appear dark? The main reason for this is that prevention of light from the objective

to the eye piece. Care should be taken when preparing the slide. If the

liquid smear taken on the slide spills over the cover slip then the smear

comes in contact with the objective and will dry out. This hinders the

passage of light. So the amount of smear taken on the slide should be

minimal and it should not come out of the cover slip. If there is excess

solution it should be drawn using tissue paper before examination. Use

distilled water or isopropyl alcohol to clean the lens and keep the lens

and the area dust free.

5. Do pebrine spores multiply in water? No, other than a few bacteria none of the pathogens of silkworm

develop in water. Pebrine spores develop only in the silkworm cell.

Therefore, the spores that enter the silkworm gut through the leaf,

germinate, multiply in the gut cell and then spread to different other

organs.

6. How to systematically destroy diseased worms?

Prepare Bleaching powder 2% / chlorofect/Seriphene/Shuchi solution

in a basin and keep. During the course of rearing, diseased worms

should be collected in the prepared disinfectant solution and then be

buried or burnt. Bed waste should be dumped at a place away from the

rearing house, covered with soil and allowed to decompose which can

be used as fertilizer after 3-4 months of fermenting. It is recommended

to keep two pits so that can be used alternatively for storing the bed

waste.

7. Worms appear healthy upto the IV stage. But grasserie or flacherie is

noticed later. Why?

For any pathogen to enter the silkworm body and disease symptoms to

appear (incubation period) is about 7-10 days. In addition, if the pathogen

load is too low then it takes still more time for the symptoms to appear.

This means that if the infection is in the chawki stage it reaches about 4th

or 5th stage for the infection to develop and external symptoms to appear.

In order to prevent this, priority should be given to rearing methods, leaf

quality, cleanliness and hygiene to prevent crop loss in the late stage.

General disinfection:

1. Variety of disinfectants is available in the market. Which is better?

In this competitive world, soaps, pastes and other things of various

brands are available. The consumer has the freedom to buy any brand.

Similarly disinfectants with different names are available in the

market. But farmers can use disinfectants such as Chlorofect, Sanitall

Plus, Sinchana, Seriphene, Bleaching powder etc. which are

recommended by any state / central government organization. Since

quality is ensured and the product is recommended only if it is found

effective againt all pathogens of silkworm.

2. What is the difference between a general disinfectant and a bed

disinfectant?

Killing of the pathogens causing diseases in silkworm is called

disinfection. This is achieved in two steps. Disinfectants such as

chlorofect, Sinchana, Seriphene, Sanitall plus, bleaching powder used

to spray the rearing house and appliances is called general

disinfection. Use of bed disinfectants such as Suraksha, Sanjeevini,

Samrakshaka, Samvardhana, Lime powder to prevent infection

spreading in the rearing bed during rearing is called bed disinfection.

3. How to estimate the quantity of disinfectants required for each rearing?

First, find the length and breadth of the house. Then, for every square

feet 0.185 ml or 1.5 lts to 2lts/per sq metre prepared solution is

required.

Ex: length = 20 ft, width = 15 ft

20’ x 15’ = 300 sq. ft.

1 sq ft requires 0.185 ml of prepared solution.

300 sq. ft x 0.185ml = 55.5 or 56 lt of prepared solution is required.

One part of concentrated chlorofect disinfectant can be mixed into 80

parts of water (earlier 40 parts).

i.e., 56/80 = 700 ml of concentrated chlorofect is mixed in 56 litres of

water and sprayed to rearing room with 300 sq ft area with appliances.

To prepare a bleaching powder solution of 2%.

20 g of bleaching powder is mixed in one liter of water.

So 56 lts requires 56 lts x 20 g = 1.12 kg.

5. Which are the different room disinfectants available in the market?

Disinfectants with different names are available in the market. Room

disinfectants recommended by the institute are Chlorine based

disinfectants -Chlorofect, Sinchana, Sanitall Plus, Bleaching powder

and phenol based disnfectant-Seriphene.

6. What are the benefits of mass disinfection? The disease causing pathogen spread from the silkworm to the rearing

environment and can survive for a long time. Under favourable

environmental condition, they germinate and cause disease. Fungal

spores are light and spread through the air, causing disease. It is

impossible to cure upon the onset of the disease. Therefore, it is

advisable to take precautions. Proper disinfection techniques and

cleanliness of the rearing house and the surroundings can prevent the

disease occurence and spread. To get the full benefit of disinfection, it

is best to disinfect a village or an area. This can prevent the spread of

the disease from one crop to another, i.e., from one rearing house to

another.

Bed disinfection:

1. Why bed disinfectants should be used during silkworm rearing, Is

lime not sufficient?

Bed disinfectants are prepared by mixing several chemicals with lime.

When bed disinfectant is dusted on silkworms and rearing bed, the

disinfectant comes in contact with the pathogens if any present and

neutralizes them. Thereby, significantly reduce the spread of infection.

Chemicals present in bed disinfectants have the capacity to kill various

pathogens of silkworm like, bacteria, viruses and fungi. The lime used

reduces the moisture content in the silkworm rearing bed. Although

lime is effective againt virus and fungus does not have the capacity to

kill all the pathogens compared to recommended bed disinfectant.

Lime should be used when worms settle for moult and bed

disinfectants to be used after the worms are out of moult and as

recommended.

2. Tell us about the currently using bed disinfectants?

Bed disinfectants are a mixture of chemicals, lime or mud and act as

contact disinfectant. Bed disinfectants should be used right from

commencement of rearing till completion of rearing as a prophylactic

measure. There are two types of bed disinfectants: (1) disease and

season specific disinfectants (2) All disease and all-season bed

disinfectants.

Disease and Season specific bed Disinfectants:

Sanjeevini: Sanjeevini bed disinfectant is used during the summer and

rainy season from March to September to prevent virus and bacterial disease.

Suraksha and Suraksha green: used to prevent fungal diseases like

Muscardine and Aspergillosis from June to February.

Bed Disinfectants for all diseases and seasons:

Samrakshaka and Samvardhana - Can be used throughout the year to

control all diseases of silkworm.

Method of use: Bed disinfectants should be used right from brushing

on empty trays and on the chawki worms. At each stage, after every

moult before first feeding bed disinfectant should be dusted. In the

fifth instar the disinfectant should be dusted on 1st day after 4th moult

and also on the 3rd or 4th day. During bed extension, bed disinfectant

should be dusted on empty trays before transferring the silkworms.

Across the state silkworm rearers use bed disinfectants to prevent diseases

and get 8 to 10 kg more yields per crop.

3. I rear silkworm by tray method and then first clean the house and

equipments with water and then disinfect it. Even then crop loss is

noticed? This method of disinfection is unscientific and improper. Hence, crop loss

occurs. Washing the rearing house and appliances with water before

disinfection do not kill the pathogens but these viable pathognes are

released to the environment during washing and thus spread the disease to

the next crop. So, it is recommended to first collect and dispose the dry

waste from the bed and allow to decompose. The rearing equipment

should then be disinfected with a good room disinfectant and allowed for

12-18 hrs. Later the rearing appliances are taken out washed with water

and dried in direct sunlight for 10-12 hours. During this time the floor of

the rearing house is cleaned by scrubbing using any disinfectant solution.

Then rearing appliances are shifted inside. Second disinfection is

conducted 1-2 days before the next rearing. Thus, scientific method of

disinfection is done twice, so that the home and equipment are free of

pathogens, so that the next crop is not infected and can get a good crop.

4. Normally diseases are noticed in the adut stage, so is it enough to use

bed disinfectant only in the last 2 stages? And why is it recommended

to dust on the empty tray?

Symptoms of any disease in silkworm appear after 3 to 10 days after

infection, i.e., if infection occurs in the 1st or 2nd stage, symptoms appear

in the 4th stage and if infection is in the 3rd stage symptom occurs in the

5th stage. Therefore, it is essential to use bed disinfectant from the chawki

stage itself as a precautionary measure to prevent disease occcurence.

Even, if the disinfection is conducted prior to start of rearing, the bed

disinfectant should be dusted on the wax paper placed on an empty tray.

This prevents infection to the just hached larvae from the egg shell.

5. Can Sanjeevini and Suraksha bed disinfectants be used

simultaneously in the rainy season to prevent both grasserie and

muscardine.

During rainy season, both grasserie and muscardine can appear. Then

using Suraksha bed disinfectant do not harm the silkowrms. Since

muscardine spreads faster in the rearing bed it is recommended to pick

the diseased silkworms as soon as they are diagnosed and transfer the

larvae to a separate tray and dust the bed disnfectant on the tray and on

the worms. Sanjeevini is dusted as per the schedule.

Cleanliness/hygiene in silkworm rearing

1. Tell us about the importance of hygiene in silkworm rearing? Maintaining hygiene inside and outside the rearing house is vital.

Farmers should keep in and around the rearing house clean. The

waste storage pit should not be close to the rearing house and the pit

should be covered with dung and soil to avoid spreading of the

pathogen through air from the dead larvae. To avoid disease spread

during the course of rearing dust bleaching powder or lime powder

around the house. During cocoon harvesting the dead larvae and other

waste should be collected into Suchi solution or any disinfectant and

then buried or burnt. After day-to-day rearing activity, the floor must

be cleaned and mopped with Suchi solution. Personal cleanliness of

the rearer is important. So, hands should be cleaned with Shuchi

solution before feeding or touching the larvae.

2. How to use Suchi hand sanitizer? Institute has developed a mild and pleasant disinfectant called

'Shuchi' which is used to clean the hands and feet before entering the

rearing house, collection of diseased larvae. It maintains cleanliness

and hygiene during rearing and does not harm the health of the users.

Mix 1 part of Shuchi in 100 parts of water (1:100 ratio) in a basin and

rinse the hand before and after touching the worms. The mixture

should be replaced every 2-3 days. Similarly, daily clean the foot

before entering the rearing house. After bed cleaning or feeding

sweep the floor, remove the litter and mop with Suchi solution. Use

Suchi solution to collect diseased and unequal larvae and dispose

them by burying or burning. It should be used as indicated on the

bottle. One liter of Suchi is required to rear 100 dfls. It should be

mixed in a ratio of 1: 100.

With regular use of Suchi, cleanliness can be maintained during

rearing hence pathogen load decreases significantly and thus prevent

the spread of disease, resulting in getting better quality of cocoons.

Other issues pertaining to diseases:

1. How to borrow the rearing trays when they are required? Each silk grower should have his own rearing appliances and

brushing should be conducted depending on the available equipments.

However, sometimes due to inevitable reasons, trays need to be

borrowed. Under such conditions the trays are disinfected and used

later. This reduces the risk of spread of infection through the tray.

2. Can the wax paper once used in rearing be reused? Wax paper is used to maintain the moisture in the rearing bed by

covering the bottom and top of the bed. Diseases such as flacherie,

grassarie, Kenchu, white flacherie, pebrine and muscardine diseases

spread through the faecla matter, skin, or body of a dead worm. In

such cases, the wax paper in the tray is more likely to be

contaminated. So wax paper should not be recycled. In this direction,

silkworm rearers should invest a small part of the earning towards

purchasing of wax paper, disinfectants, news paper, gunny cloth etc.

and get better cocoon crop yield

3. How many days after the infection of silkworm germs show

symptoms of the disease? A conducive environment should be available for any pathogen to

multiply and cause a disease. Aspergillus a fungal disease can be

noticed in 2-3 days in chawki worms when the high temperature and

humidity is present. At low temperatures and high humidity

muscardine can be seen in 3-4 days in chawki stage and 5-7 days in

adult stage. Symptoms become clear within 5-6 days after infection

due to grassarie disease. Kenchu disease can manifest in 8 to 10 days

after infection. Pebrine is noticed in 10-12 days if infection is in the

1st instar and and if infection is in the adult stage infected moths

occur. In Flacherie Sotto disease symptoms occur in 24- 48 hrs and

other bacterial flacherie disease appear within 3-4 days. The disese

occurrence depends on the pathogen load in the environment and in

the larva.

4. What type of lime should be used in silkworm rearing?

Hydrated lime should be used. It contains less than 3% of water and

more than 85% of calcium oxide. Only such lime has the ability to

absorb moisture from the atmosphere. Hence, it should be stored in

plastic containers.

5. What are the uses of lime?

Reduces the moisture content in the bed by absorbing it.

It causes leaf driage in the rearing bed.

Absorb bad gases released in the rearing house.

Helps to dry the bed and destroy the pathogens in the rearing bed and

silkworm body.

6. How should lime be used in silkworm rearing? About 4-5 hours after the silkworms have settled for moult, lime

should be dusted thoroughly on the silkworm body and bed using a

thin cloth.

In the adult stage lime can be used for dusting. If the humidity is high

in the bed and in the atmosphere, lime should be dusted every

morning before feeding.

7. Can lime be used every day? There is no need to dust lime every day. It should be used once every

moult, and 1-2 times in the last stage. Twenty-five per cent more lime

is required in the shoot system of rearing than in the tray method. Lime

can be used on alternate days when there are more unequal silkworms,

diseased silkworms in the bed.

8. What is the most important precautionary measure to be followed in

silkworm rearing? Disinfection before and after rearing.

Egg incubation and black box treatment.

Provide good quality mulberry leaf timely and maintain temperature,

humidity and adequate bed space depending on the age of the larva.

Maintain cleanliness and hygiene in the rearing area.

Allow the worms to settle for moult properly and dust lime powder on

the bed and keep the bed dry.

Use bed disinfectants after silkworms are out of moult.

Comprehensive management of disposal diseased worms.

9. Is there any relationship to incidence of pests in the mulberry garden

to diseases of silkworm?

Diseases of silkworm like muscardine, pebrine and Kenchu is noticed

in the pests of mulberry like Bihar hairy caterpillar, leaf roller, cut

worm. These pathogens are thrown out of the body along with the

faeces/ blood and dead insects. The pathogens from the pests enter the

body of silkworm through the mulberry leaf and develop in the

intestinal tract of the silkworm and cause disease. Therefore, pest free

mulberry garden should be maintained to control transfer of disease

from the pest to the silkworm.

10. Can lime be used in all seasons of the year? There is always moisture in the worm bed that is transferred through

the leaf. If the bed is thick or during rainy season humidity is more than

90%. Therefore, lime can be used for all seasons in a year and reduce

moisture in the bed. Even if the amount of lime used is slightly higher,

the crops are not affected. It requires more quantity of lime in the rainy

season than in the summer and winter.

11. Does too much lime dust close the respiratory pores and affect the

silkworm?

The pores of the spiracle are covered with hair and this will not block

the respiratory pores. Even if the hole is closed, the dust is ejected. If

silkworms eat a small quantity of lime it will not affect the health of

silkworm.

12. Are worms affected by lime powder present on the mulberry leaf?

Under normal conditions, lime powder does not fall on the leaf that

silkworms eat. This is because the lime is dusted on worms that have

stopped eating and even if the worm eats a quantity of lime it will not

cause any harm.

13. What is the method by which farmers test the quality of lime? “Lime Check”, is the technology recommended by KSSRDI where the farmer's

can check the quality of Lime.

14. What are the methods for testing the quality of bleaching powder? The concentration of chlorine in bleaching powder should be 30 to

33%. The concentration of chlorine decreases when packing,

repacking and if it is exposed to air. Farmers can check the quality of

bleaching powder using Bleach Check Kit.

15. I had a good crop for 4-5 years after constructing the new rearing

house, even without using any disnfectants but now since one year I

am loosing crop due to grasserie and flacherie? About 5-6 crops can be taken in a year. In each crop, pathogens from

dead worms spread to the rearing room, appliances, and the

environment. This causes an increase in the number of pathogens in

the environment, as a result the mortality rate increases gradually,

reaching the stage where the entire crop is lost. To prevent this, it is

necessary to disinfect each crop twice, i.e. after completion of the crop

and two days before brushing. Steps are to be taken to grow good

quality leaf.

16. What should be done to store the bamboo trays?

In the case of tray method, the cleanliness and disinfection of the tray

is crucial, as pathogens from dead worms and faecal matter become

the main source of infection. Usually, farmers use cowdung to swab

the bamboo trays and dry them in the sun for it to last long. When

trays are placed in the sun, the pathogens die from the heat of the sun

(sunrays) and ultraviolet rays. Entry of sun light to the dung and

killing the germs is partial. So, mixing bleaching powder / lime / or

any disinfectant with the dung and then placing the trays in direct

sunlight will improve in killing the pathogens present in the tray.

17. Sometimes the larvae die within a few hours of feeding. What is the

reason for this? The main reason for the worms to vomit and die within a few hours of

feeding is due to the consumption of poisonous mulberry leaf. The

pesticide or the bacteria B. thuringensis suspension if sprayed to

vegetabe or fruit adjacent to mulberry garden, the spray drifts along

with the wind and the worms that eat such leaf die instantly. This can

be reassured by the farmers by feeding the problematic leaf to about

few healthy larva and testing. If mortality is observed then it is

confirmed that the death is due to poisoning and nessary measures are

to be taken.

18. During winter season I keep the windows covered with blankets to

keep the rearing room warm. Some say it is not correct to cover the

windows. Why? During winter and rainy season temperature is low and humidity is

high in the environment. Fungal pathogens causing white and green

muscardine multiply under such condition. If the windows of the

rearing house is closed or covered with blanket entry of clean air and

light is restricted. Hence, moisture in the rearing tray increases and in

addition the harmful air like CO, CO2 emitted by the worms get

accumulated. This makes the silkworms weak and get more quickly

infected. For these reasons, farmers should use an electric heater or

charcoal heater to maintain optimum temperature and humidity during

winter and rainy season. Care should be taken to keep the smooth

entry of air and light.

19. When there is availability of leaf, the chawki and adult silkworms

were reared in the same room and larval death was noticed in both

the batches. Why?

The temperature and humidity, quality of the leaf required for chawki

and adult silkworms is entirely different. Any variation these

parameters affect the growth and immunity of the larvae right from the

young age and symtomps are noticed in the adult stage. The infection

from adult larvae gets transferred to the chawki silkworms if reared in

the same room. According to a survey conducted, the rate of infection

in chawki stage doubles when the larvae reach mature stage, leading to

higher crop damage. Hence, young and adult age silkworms should

not be reared in the same room.