CONTENTS

 Introduction
 Sericulture definition
1. What is sericulture?
2. What is silk?
3. Why sericulture?
4. Where do we find silk?
 Classification of silk and silkworms
 Life cycle of silkworm
 Trends in Indian sericulture
 Pets and disease control of mulberry silkworm
 Diseases of mulberry silkworm and their control
5. Viral diseases
6. Bacterial diseases
7. Fungal diseases
8. Protozoan diseases
9. Other miscellaneous diseases
10.Integrated control of silkworm diseases
 Pests of mulberry silkworm and their control
11.Major pests
12.Minor pests
 Potential, strengths and challenges of sericulture industry in India
13.Seri-bio-diversity
14.Sericulture and national economy
15.Sericulture and women empowerment
16.Sericulture and rural development
17.Steps to improve productivity and quality
18.Growth rate and demand for silk
19.Research and development
20.Amendment to central silk board act
21.Textile policy of government of India
22.Mapping and Selection of Suitable Areas
 Technical terms associated with silk cultivation
 Reference
Introduction
India enjoys a unique distinction of being the only country in the world producing all the
varieties of natural silk, viz., Mulberry, Eri, Tasar, Oak and Muga. Silk is the most elegant textile
in the world with unparalleled grandeur, natural sheen, and inherent affinity for dyes, high
absorbance, light weight, soft touch and high durability and is known as the queen of textiles
the world over. The Indian silk industry has seen many ups and downs. During the 18th, 19th
and early 20th centuries sericulture flourished in the states of Bengal, Mysore and Kashmir.
During the Second World War silk production was promoted for making parachutes. Planned
efforts of the Government of India in the post-independence period gave a thrust as a tool for
rural employment, poverty alleviation and export earnings which gave a big boost to the
industry. At present, it is estimated that every hectare of mulberry provides employment to
about 16 persons. Concerted research and development efforts and expansion brought the raw
silk production from 1437 MT in 1951-56 to 17351 MT in 2001-02 though it remained almost
static during X Plan. However, the productivity has gone up from 16 kg to 85 kg raw silk per ha /
year. Silk contains 70-75% fibroin and 25-30% sericin protein. Natural colour of Eri, brick red or
creamy white or light brown. Silk has all desirable qualities of textile fibres, viz. strength,
elasticity, softness, coolness, and affinity to dyes. Silk fibre can elongate 20% of original length
before breaking. Silk is poor conductor of heat and electricity. However, under friction, it
produces static electricity. Silk is sensitive to light and UV- rays. Silk fibre can be heated to
higher temperature without damage. It becomes pale yellow at 110 ºC in 15 minutes and
disintegrates at 165 ºC.
China, producing 102,560 MT (81.65%) of raw silk is the largest exporter where as India,
contributing about 13 percent of the world’s raw silk production, is the largest consumer. The
high quality and low price are the strengths of Chinese silk while the traditional practice of
wearing silk clothing on all auspicious days has been the strength of the Indian silk in the
domestic market and the exclusive designs in the international markets. Indian exports are
largely dependent on the import of quality silk from China. India too has seen a conspicuous
decline in the area under mulberry between 1990-92 (3, 31,237 ha) and 2004-05 (1, 71,959 ha).
Though the decline in the cultivated area and the raw silk production during 2002-2004 was
largely attributed to drought and dumping of Chinese silk at cheap prices, the decline in the
area under mulberry could be very well attributed to the lowering water table in the traditional
silk producing areas, prompting them to switch over to horticulture crops, requiring the least
quantity of water and urbanisation. This has been prominently visible in the traditional areas of
Karnataka. Though there has been a steep decline in the area under mulberry, this has been
somewhat compensated by the productivity which has gone up to around 85 kg of raw silk per
hectare per year due to introduction of highly productive mulberry and silkworm breeds.
During the past two years, the raw silk production has picked up and touched 17,305 MT during
2005-06 (almost the same as that prevailing at the end of the IX Plan) and it is likely to cross
18,500 MT by the end of the X Plan. With many Business Process Outsourcing (BPO) and
manufacturing units coming up in urban areas, the scope of developing sericulture largely
remains with the rural areas off the urban habitation.

What is Sericulture?
Sericulture is an agro-based industry. It involves rearing of silkworms for the production of raw
silk, which is the yarn obtained out of cocoons spun by certain species of insects. The major
activities of sericulture comprises of food-plant cultivation to feed the silkworms which spin silk
cocoons and reeling the cocoons for unwinding the silk filament for value added benefits such
as processing and weaving.
Although there are several commercial species of silkworms, Bombyx mori is the most widely
used and intensively studied. According to Confucian texts, the discovery of silk production by
B. mori dates to about 2700 BC, although archaeological records point to silk cultivation as early
as the Yangshao period (5000 – 10,000 BCE).By the first half of the 1st century AD it had
reached ancient Khotan, and by AD 140 the practice had been established in India. Later it was
introduced to Europe, the Mediterranean and other Asiatic countries. Sericulture has become
one of the most important cottage industries in a number of countries like China, Japan, India,
Korea, Brazil, Russia, Italy and France. Today, China and India are the two main producers,
together manufacturing more 90% the world production each year.

What is Silk?
Man is always inquisitive for silk products. SILK - The Queen of Textiles, spells luxury, elegance,
class and comfort. Mankind has always loved this shimmering fibre of unparalleled grandeur
from the moment Chinese Empress Shiling Ti discovered it in her tea cup. It withstood many a
daunting challenges from other natural and artificial fibres and yet, remained the undisputed
Queen of Textiles since centuries. Exquisite qualities like the natural sheen, inherent affinity for
dyes and vibrant colours, high absorbance, light weight, resilience and excellent drape etc. have
made silk, the irresistible and inevitable companion of the eve, all over the world.
Chemically speaking, silk is made of proteins secreted in the fluid state by a caterpillar,
popularly known as 'silkworm'. These silkworms feed on the selected food plants and spin
cocoons as a 'protective shell' to perpetuate the life. Silkworm has four stages in its life cycle
viz., egg, caterpillar, pupa and moth. Man interferes this life cycle at the cocoon stage to obtain
the silk, a continuous filament of commercial importance, used in weaving of the dream fabric.

Why Sericulture?
The major benefit of the sericulture especially Tasar is the employment generation to the
people specially in forest areas like tribal. Income from the forests leads to sense of protection
and conservation of areas.
1. High employment potential
About 60-100 lakh persons are engaged in various sericulture activities in the country
It is estimated that Sericulture can generate employment @ 11 man days per kg of raw silk
production (in on-farm and off-farm activities) throughout the year. This potential is par-
excellence and no other industry generates this kind of employment, especially in rural
areas, hence, sericulture is used as a tool for rural economy upliftment.
Provides vibrancy to village economies
About 57 % of the gross value of silk fabrics flows back to the cocoon growers with share of
income to different groups.
56.8 % to cocoon grower

6.8% to the reeler

9.1% to the twister
10.7% to the weaver
16.6% to the trade Thus, large chunk of income goes back to the villages from the cities.

2. Low Gestation, High Returns

Mulberry takes only six months to grow for commencement of silkworm rearing. Mulberry
once planted will go on supporting silkworm rearing year after year for 15-20 years
depending on inputs and management provided.
3. Five crops can be taken in one year under tropical conditions.
By adopting stipulated package of practices, a farmer can attain net income levels up to
Rs.50000 per acre per annum. Hardworking farmers with proper maintenance and inputs
can reach up to an income of 2 lac per year from one acre.
4. Women friendly Occupation

Women constitute over 60 % of those employed in down-stream activities of sericulture in

the country. This is possible because sericulture activities starting from mulberry garden
management, leaf harvesting and silkworm rearing is more effectively taken up by the
women folk. Even silk reeling industry including weaving is 100% supported by them .

5. Ideal Program for Weaker Sections of the Society

6. Sericulture can be practiced even with very low land holding. One acre of mulberry
garden and silkworm rearing can support a family of five without hiring labour.
7. Features such as low gestation, high returns make sericulture an ideal program for
weaker sections of the society.
8. Vast tracts of forest based tasar food plantations available in the country, if judiciously
exploited for rearing tasar silkworms, can offer supplementary gainful employment for
tribals.

9. Eco-friendly Activity
10. As a perennial crop with good foliage and root-spread, mulberry contributes to soil
conservation and provides green cover. Waste from silkworm rearing can be recycled as
inputs to garden. Dried mulberry twigs and branches are used as fuel in place of firewood
and therefore reduce the pressure on vegetation/forest.
11. Being a labour intensive and predominantly agro-based activity, involvement of smoke-
emitting machinery is minimal.
12. Developmental program initiated for mulberry plantation are mainly in upland areas
where un-used cultivable land is made productive.
13. Mulberry can also be cultivated as intercrop with numerous plantations.
14. Mulberry being a deep-rooted perennial plant can be raised in vacant lands, hill slopes
and watershed areas.
15. Currently, only about 0.1 % of the arable land in the country is under mulberry
cultivation.
16. Satisfies Equity Concerns
Benefits of sectoral value-addition primarily accrue to rural households. As the end-product
users are mostly from the higher economic groups, the money flows from high end groups
to low end groups.
Cases of landless families engaged in cocoon production using mulberry contracted from
local farmers are common in some states.

Mulberry farming is also done on community, government lands where the landless are
given limited rights to cultivate mulberry.

Where do we find Silk?

Geographically, Asia is the main producer of silk in the world and produces over 95 % of the
total global output. Though there are over 40 countries on the world map of silk, bulk of it is
produced in China and India, followed by Japan, Brazil and Korea. China is the leading
supplier of silk to the world.
India is the second largest producer of silk and also the largest consumer of silk in the world.
It has a strong tradition and culture bound domestic market of silk. In India, mulberry silk is
produced mainly in the states of Karnataka, Andhra Pradesh, Tamil Nadu, Jammu & Kashmir
and West Bengal, while the non-mulberry silks are produced in Jharkhand, Chhattisgarh,
Orissa and north-eastern states.
Silkworm larvae are fed mulberry leaves, and, after the fourth moult, climb a twig placed
near them and spin their silken cocoons. The silk is a continuous-filament fiber consisting of
fibro in protein, secreted from two salivary glands in the head of each larva, and a gum
called sericin, which cements the two filaments together.
 The sericin is removed by placing the cocoons in hot water, which frees the silk filaments
and readies them for reeling. The immersion in hot water also kills the silkworm pupae.
Single filaments are combined to form thread. This thread is drawn under tension through
several guides and wound onto reels. The threads may be plied together to form yarn. After
drying the raw silk is packed according to quality.

Types of Silk
There are four major types of silk of commercial importance, obtained from different
species of silkworms which in turn feed on a number of food plants. These are:

A. Classification based on species. All are different species.

1. Mulberry
2. Oak Tasar & Tropical Tasar
3. Muga
4. Eri

India produces all three varieties of natural silks viz silk, Tasar silk, Muga silk and Eri silk. The
Tasar, Eri and Muga silk are non mulberry silks which are wild silks and also known as Vanya
Silks. Silk has luster, drape and strength. There are three grades of silk; each is a product of
the three different stages of silk processing. The unwound filament makes the finest quality
silk, and is referred to as reeled silk. It is satiny smooth and pure white. Remaining silk from
the reeling process becomes the raw material for carded or combed, spun silk yarn. The
short fibres left behind after the carding or combing process are used to make noil yarn, a
richly textured nubbly silk.
In unparallel textures, with natural sheen, easy affinity for natural dyes, light in weight and
high in moisture absorbency, and with baffling thermal properties…warm in winter and cool
in summer, products of rich, salubrious climate and nourishing vegetation, each of the
Vanya silks has its own unique beauty and ethnic culture. They are distinguished in four
different forms: muga, tropical tasar, oak tasar and eri. They are the magnificent gifts of
nature to genius of global designers, to explore and create various designs for garments, life
style products and home furnishings for sophisticated homes, haute couture as far as
artistic imagination can stretch.
Variety-wise raw silk production

1. Mulberry Silk:
Mulberry silk is the most popular and widely cultivated one produced by the insect, Bombyx
mori, feeding exclusively on the leaves of mulberry (Morus spp). Depending on the number
of generations it passes in a year they have been termed as univoltine (with one
generation), bivoltine (two generations) and multivoltine (many generations). Univoltines
and bivoltines are adapted to temperate regions matching with the availability of fodder,
which depends on the growth and dormancy of the food plants resulting from the climatic
changes. They are known to yield high quantities of high quality silk, but are sensitive to
warmer temperature, excessive humidity and other environmental stress. Multivoltines are
well adapted to tropical situations where mulberry grows and produces fodder throughout
the year. These silkworm breeds are tolerant to higher temperature, humidity, diseases and
other stresses, but are poor yielders. Bivoltine hybrids are reared largely in the temperate
regions such as Jammu & Kashmir, Himachal Pradesh, Uttaranchal, a few pockets in the
eastern/north-eastern region and to a limited extant in Karnataka, Andhra Pradesh and
Tamil Nadu. Multivoltine reeling cocoons are produced exclusively in West Bengal and parts
of Assam. About 95 percent the silk produced in the country is that of cross breed
(multivoltine x bivoltine) including marginally multivoltine silk and the bivoltine silk is
around 5 percent.
Mulberry silk worm

2. Tasar Silk:
Tasar silk is largely produced by the tropical insect, Antheraea mylitta and to a little extant
by the temperate insect, Antheraea proylei. They feed on a wide range of species of food
plants. The tropical tasar silkworms feed mainly on Asan (Terminalia tomentosa), Arjun (T.
arjuna) and Sal (Shorearobusta). The temperate tasar is also known as oak tasar as the
worms feed on many species of Oak (Quercus spp). Tasar silk is copperish and much
stronger. Tropical tasar is produced in Jharkhand, Chattisgarh, Madhya Pradesh, Orissa and
Bihar and to a small extant in Maharashtra, West Bengal and Andhra Pradesh. Oak tasar is
cultivated in the sub- Himalayan belt covering the States of Manipur, Himachal Pradesh,
Uttar Pradesh, Assam, Meghalaya and Jammu & Kashmir.
India is the second largest producer of tasar silk and the exclusiveproducer of Indian tasar
(also known as tropical tasar) which is largely tended by tribals in the Gondwana belt. Oak
tasar (also known as temperate tasar) is mainly used for furnishing, dress materials and
sarees. Bomkai, Paithani, Ikkat (tie & dye) and Katki are some popular fabrics produced
using tasar silks. Bafta is a popular blend of tasar and cotton. Shawls and mufflers are also
produced using a blend of oak tasar and other natural fibers like wool, cotton, etc.
Tasar silk is basically a forest produce and was practiced by adivasis and tribals from time
immemorial in tropical belts even prior to introduction of mulberry silk in India. Migration
to urban areas and deforestation has therefore an adverse affect on tasar silk production.
Approximately 30 percent of the tasar silk was obtained from nature grown eco-races like
Railey, Laria, Sarihan, Modal, etc. which are solely wild and not amenable to human
handling. Over exploitation of these races and introduction of cultivated eco-races from
other areas resulting in the neglect of these local races resulted in their dwindled
production. ‘Daba’ is the most amenable eco-race largely cultivated in tropical India.
Though there is no recorded document available regarding the origin of tasar in India, one
can find the mention of tasar silk in ancient epic Ramayana "Ram’s nuptial gift to Sita
includes tasar silk". Temperate tasar is of recent origin and was introduced during mid
1960's.
Following steps are involved in Tasar cultivation Process in Nutshell
The beneficiaries are given a certain quantity of eggs which they nurture (rear) in selected
forest areas. After the silkworms form a cocoon the cocoons are collected and bought by
the department or an outside agency. The whole cycle takes about 40 to 45 days. The
process stars immediately with the onset of monsoon as the humidity builds .During the
period the beneficiaries protect the larvae from parasites such as birds, monkeys, snakes
and diseases. The second crop starts immediately after the fist crop is over as there is
enough humidity left. Process in detail is as follows. In various parts of the country the
process is adopted by joint forest management committees.

1. Selection of forest areas – Forest areas where a certain minimum of 500- 1000 tasar food
tree like saja and arjun should be selected. Care should be taken that there is enough tree
leaves in the crop. In order to manage larvae transfer large tree should be avoided.

2. Selection of Beneficiary- beneficiaries should be selected from local villages who know
the topography and the forest. They should be willing to invest their whole time for 45 days
in the forests. Every beneficiary is given 200DFLs for rearing. A normal dense forest with
about 3000-4000 trees per hectare is sufficient for 200DFLs. But in case of acres of scares
patches the area allotted to a beneficiary for 200DFls should be increased by equivalent
proportion.
3. Training- The beneficiaries have to be trained as Tasar rearing is an specialized process.
normally the beneficiaries are trained in the first crop.
4. Preparing the site – Then forest area which is selected has to be cleaned for bushes and
weeds so that insects and other fauna are minimized. The ground has to be disinfected for
disease and the leaves are also disinfected for disease like gall .
5. Inoculation of eggs - Every beneficiary is given 200 DFL,s. A DFL is a defined as Disease
Free Laying that is a group of eggs laid out by a moth which has been certified as disease
free. Normally it consists of 200 healthy eggs. These eggs are initially put over a small shrub
of tasar food tree and are covered by net for protection from predators. After a week of
hatching they are transferred and spread to other tasar food trees. The process of initial
hatching and rearing of tasar eggs is called Chawkie rearing.

6. Food Plant Management- The larvae are transferred from tree to tree as they continue
to feed. A typical larva eats up to 30 times of its final weight.
7. Spinning- After about 30 to 35 days the larvae starts to make cocoon. This process is
called spinning. it takes about 2 to 3 days. It then settles inside the cocoon as a pupa. The
cocoons are collected and are ready for either reeling or for next crop.
8. Grainage - Since there is enough humidity in the atmosphere the pupa after 7 days comes
out as moth and the cycle is repeated. By the end of the second crop the winter season
begins hence there is not enough humidity and temperature for next cycle to begin. Hence
in this case the pupa inside goes for diapauses till next monsoon. Good quality cocoons
depending upon next year requirement are stored as seed cocoons rest are used for reeling
to be converted into thread and raw silk.

9. Seed Crop and commercial crop- The first crop with the onset of monsoon is called Seed
Crop as it provides eggs for the next crop. The quality of the cocoon is poor and has lot of
moisture. The second crop is called Commercial Crop as the quality is good.

Economics of tasar cultivation

1. A beneficiary is given one hectare of forest land or an equivalent area for 200DFLs. An
equivalent area for Tasar cultivation is about 5000 tasar trees per hectare. If suppose there
are 2500 trees per hectare then 100 Dfls will be used and it will be half hectare in
equivalency.

2. Each DFL contains 200 healthy disease free eggs.

3. Each egg has the potential to become full grown cocoon. Therefore theoretically a group
of 200 DFLs can gives 40,000 cocoons.
4. But actually there are hatching losses about 10% and depending upon the care taken by
beneficiary losses due to predators and weather losses.
5. Normally in traditional areas the output is about 50 cocoons per 200DFLs.
6. Normally the price of a cocoon varies from lowest grade 30 paisa to 2 Rupees. Therefore
the average cost of the produce is about 1 Rupee.
7. Therefore a beneficiary in one crop gets about Rs 10000 in 45 days.
8. The yield in the second crop is higher and the beneficiary may earn up to 15- 25000 in
second crop.
9. Therefore a beneficiary in two crops may earn between 25,000 to 50,000.
10. In traditional areas some beneficiaries earn up to between 1 to 2 lacks working in family
groups.
11. Due to the presence of the beneficiaries the forests are protected as the income of the
beneficiaries depend upon the abundance of food plants.
12. The production of cocoons in the forest areas leads to development of other
decentralized cottage industries like reeling, dyeing and weaving.
3. Muga Silk:
The pride of India, muga silk is known for its natural shimmering golden colour. Its
production is confined to Assam, border areas of neighboring Northeastern states and
Cooch Bihar in West Bengal. It is produced by the muga silkworms (Antherae aassamensis),
which feed on Som and Sualu. The most expensive of silks, muga is intrinsically woven into
the cultural traditions of the people of Assam. The vibrant Sualkuchi sarees and mekhla-
chaddars are the traditional items made from muga silk. In recent times, fashion designers
have found exciting prospects in using muga silk for developing new products and designs.
Use of muga yarn as a substitute for ‘zari’ in sarees is finding favor with reputed weavers.

The silk of Assam (Muga) was made known to the World during 1662 through a famous
European traveler Jean Joseph Tavenier. Sericulture was exempted from payment of land
revenue as the Kings of Assam patronized the development of sericulture. Around 1950,
there was a great earth quake in Upper Assam and the large number of muga plantations
was destroyed, which hampered the growth of muga industry.
Muga silk is obtained from the silk insect, Antheraea asama, which looks similar to the tasar
silk insects. It is multivoltine with 5 to 6 broods per annum and feeds on a wide range of
species of food plants, important of which are Som (Perseabombycina) and Soalu (Litsea
polyantha). Though the silkworms are grown outdoors on the trees, mature silkworms crawl
down the trees when they are picked up and placed on dry twigs serving as mountages
indoors. This is cultivated extensively and almost exclusively in Assam and a few north-
eastern states. The cocoons are fawn coloured while the reeled silk is of golden yellow.

4. Eri Silk:
Also known as endi or errandi, this silk is produced by the eri silkworm (Philosamiaricini).
The very name ‘Eri’ is derived from the Sanskrit word, ‘Eri’ or ‘Erandi’ which means castor
(Ricinus communis). It is also known as ‘Endi’ in Assam. It is cultivated on Kesseru
(Heteropanax fragrans), Tapioca (Manihot utilissima) also known as Cassava, Payam (Evodia
fluxinifolia), Barkesseru (Ailenthusspp), etc. It tops the non-mulberry silks in production.
Samia ricinii (Referred to as Philosamiaricinii in earlier occasions) is the only cultivated eri
silkworm in the world. It is a multi-voltine silkworm with 4 to 6 broods a year.
The cocoons are non-reelable and therefore spun into yarn looking like cotton. Eri cocoons
are comparable to the cut/pierced mulberry cocoon in terms of value and do not stand well
in comparison to mulberry culture in terms of return from unit area in southern India. But, it
has been an integral part of the culture of Assamese and many others in the north eastern
states and a few pockets in the adjoining eastern states where the pupae are relished
cuisine at par with other meats; and the silk which is as warm as wool is used in making
warm clothing particularly in the form of chadders. Though a large number of people
cultivate eri silkworms, it is in a very small scale, often between 25-50 disease free layings
(dfls) on nature grown food plants. Systematic cultivation of annual food plants like castor
or tapioca exclusively for cocoon production remains uneconomical. Bulk of eri silk is
produced in Assam and to a small extant in Bihar, West Bengal, Orissa and Manipur. Central
Silk Board initiated intensive efforts to introduce ericulture in the non-traditional states
where castor and tapioca are traditionally grown for oil seed and tubers on castor and
tapioca as a subsistence activity utilising part (25-30 percent) of the leaves by extending
support for castor cultivation and start up tools.
Eri culture was mostly confined to the Brahmaputra valley of Assam in the tribal inhabited
districts, followed by Meghalaya, Nagaland, Mizoram, Manipur and Arunachal Pradesh.
Ericulture is introduced on a pilot scale in States like Andhra Pradesh, Tamil Nadu, West
Bengal, Bihar, Chhattisgarh, Madhya Pradesh, Orissa etc.

B. Classification based on occurrence.

1. Domesticated - Mulberry, Reared tasar
2. Wild- Tasar, Muga and Eri. Wild silks are also called Vanya Silk.

C. Classification based on Ecoraces

1. Mulberry - Various geographic varieties.
2. Tasar-Natural, reared.
D. Classification based on life cycles per year.
1. Multi Voltine - More than 2 lifecycles per year. Mulberry and tasar in central and south
India.
2. Bi Voltine - Two life cycles per year. Tasar in Tropical areas. Mulberry in tropical areas as
an improved variety.
3. Uni Voltine - One life cycles per year. Oak tasar and Mulberry in temperate areas.
Kashmir, Himachal and China
India produces all three varieties of natural silks viz silk, Tasar silk, Muga silk and Eri silk. The
Tasar, Eri and Muga silk are non mulberry silks which are wild silks and also known as Vanya
Silks. Silk has luster, drape and strength. There are three grades of silk; each is a product of
the three different stages of silk processing. The unwound filament makes the finest quality
silk, and is referred to as reeled silk. It is satiny smooth and pure white. Remaining silk from
the reeling process becomes the raw material for carded or combed, spun silk yarn. The
short fibres left behind after the carding or combing process are used to make noil yarn, a
richly textured nubbly silk.

In unparallel textures, with natural sheen, easy affinity for natural dyes, light in weight and
high in moisture absorbency, and with baffling thermal properties…warm in winter and cool
in summer, products of rich, salubrious climate and nourishing vegetation, each of the
Vanya silks has its own unique beauty and ethnic culture. They are distinguished in four
different forms: muga, tropical tasar, oak tasar and eri. They are the magnificent gifts of
nature to genius of global designers, to explore and create various designs for garments, life
style products and home furnishings for sophisticated homes, haute couture as far as
artistic imagination can stretch.
Life cycle of silk worm:

Life cycle of Silkworm- Four Stages

Egg – In the first stage of the lifecycle, the female moth lays eggs, which marks the beginning of the
lifecycle. The eggs of silkworms are microscopic and can be barely seen with naked eyes. At once,
350 to 400 eggs are laid by a female moth. The egg-laying process takes place once a year. The
adequate temperature for the eggs to hatch is warm.

Larva– After the eggs are hatched, they form larva. The larva stage lasts from 24-30 days and it is
hairy. Larva depends on mulberry leaves for food and nutrition. The maximum growth of the larva
takes place in this place.

Cocoon– After 30 days the cocoon stage starts. During this stage, the Silkworm weaves a
protective covering around itself. This protective layer is called a cocoon. In a cocoon, the protective
layer is made up of a thin yarn-like structure called silk. From one cocoon a cotton ball size silk can
be obtained.

Pupa- The motionless stage of the silkworm is called the pupa. The Silkworm shows no motion
during the pupa stage. From the pupa, stage silk is loosened from the cocoon. The cocoon is boiled
in boiling water, Killing the pupa and leaving the silk behind.
Silkworm– This is the last stage of the lifecycle of the silkworm. The transformation from pupa to
silkworm takes place within 10-14 days. When it develops fully into an adult, the moth releases a
chemical called pheromones which attracts mating partners. Which results in the laying of eggs by
the female moth.

Trends in Indian sericulture:

Over the last six decades Indian silk industry has registered an impressive growth, both horizontally
and vertically. Plans and schemes implemented by central and state agencies and relentless efforts
of thousands of dedicated persons in the fields of research and extension have helped in this
context. For instance, the age old multivoltine hybrids have been replaced by multivoltine ×
bivoltine and bivoltine hybrids. The sericulture industry has witnessed a quantum jump in raw silk
productivity. The average yield of 25 kgs of cocoons/100 dfls in the recent past has increased and
currently the average yields are in the range of 60 – 65 kgs/100 dfls. The new technology, besides
doubling yields has also led to qualitative improvements in cocoon production with considerably
reduced renditta and has also helped break the climate barrier.

The market share of Indian silk exports in the global silk trade is 4 – 5 % which is not significant
considering the fact that India is the second largest producer of raw silk. This is because India has a
large domestic market for silk goods and about 85 % of silk goods produced are sold in the domestic
market. However, India exports approximately 15 % of its output of all types of silk goods (including
value-added items). The export of Indian silk products consists of finished goods like fabrics, made-
ups, ready-made garments and furnishing materials like curtains, carpets, bed spreads, cushion
covers etc. The export of silk products has been showing a steady growth and the export earnings
showed a rapid increase during the last decade.

PETS AND DISEASE CONTROL OF MULBERRY SILKWORM

Diseases of mulberry silkworm and their control
Mulberry silkworm Bombyx mori is affected by anumber ofdiseases caused by viruses,
bacteria, fungi and protozoa. These diseases are known to occur in almost all the silkworm
rearing areas of the world causing considerable damage to the silkworm cocoon crop. A
number of measures have been suggested for the prevention and control of these diseases,
but none of them has proved to be fool-proof with the result that one has always to be
careful to eliminate the cause of primary infection as well as to prevent the cross infection.
Care is also needed to be taken to see that they are not exposed to stress conditions like
adverse temperature and humidity,badventilation and nutritional deficiency which may
make them easily susceptible to various diseases.

1. Viral diseases
Viral diseases ofsilkworm pose a major problem to sericulture as they account for
almost 70 per cent of the total loss due to diseases. Viral diseases of silkworm comprise
of inclusion and non-inclusion types. The inclusion virus diseases form typical inclusion
bodies. They are Nuclear polyhedrosis and Cytoplasmic polyhedrosis which can be more
easily identified through ordinary microscopy.
 The non-inclusion type consists of Infectious flacherie and Densonucleosis which can be
detected only through electron/fluorescent microscopy and serological tests.

1.1 Nuclear polyhedrosis

It is one of the most serious virus diseases in tropical countries and occurs throughout
the year. This disease is otherwise known as Grasserie, Jaundice, Milky disease, Fatty
degeneration and Hanging disease.

Causes of the disease This disease is caused by Borrelinabombycis virus belonging to the
sub-group A of the family Baculoviridae. As the nameimplies, thisvirus multiplies and
forms polyhedra in the nucleus of the tracheal epithelial cells, adipose tissue cells,
dermal cells andbloodcells. Occasionally the nucleus ofthe middle and posterior portion
of silkgland cells are also affected. Theviral particles are rod shaped and the size 1s
around 330 x 80 nm. The size of the polyhedravariesfrom3-6μ. The shape is usually
octahedral or hexahedral and sometimes tetragon ortngon. Infection mostly takes place
through feeding of polyhedra contaminated mulberry leaf, rarely through wounds. Heat,
cold and chemical treatments have also been known to induce this disease. Factors
influencing the outbreak of this disease are high temperature and humidity, their
sudden fluctuations, bad ventilation in the rearing room, ineffective disinfection of
rearing room and equipments and feeding of tender leaves during late instars.
Inadequate larval spacing, starvation and excessive moisture in the rearing bed have
also been known to contribute towards the outbreak and spread of the disease.

Symptoms: During early part of the disease no symptoms are noticed except the worms
being slightly sluggish. Initially the skin shows oily and shining appearance. As the
disease advances the skin becomes thin and fragile and the body becomes milky white
with intersegmental swellings. The fragile skin is prone to rupture easily, liberating the
liquified body contents containing innumerable number of polyhedral which become
the source of secondary contamination. Another characteristic symptom of this disease
is that the larvae become restless and crawl aimlessly fill Grasseri affected larvae (early
stage). Grasseri affected larvae (late stage) along the ridges or rims ofrearingtrays,
subsequently falling on the ground and dying. Death takes place after infection in about
4-5 days in the young larvae and 5-7 days in the grown-up larvae. Diseased larvae lose
the clasping power ofabdominallegsexcept thecaudal legs by which it hangswith
thehead downwards. If the infection is earlv the worms fail to spinthe cocoons and die,
where as if the infection is late they are able to spin the cocoons but die inside
producing melted cocoons. Grasserie affected larvae crawlingon the edges of tray.
Grasserie affected larva hanging with head downwards.

Prevention and control: For effective prevention ofthis disease, the silkworm rearing
rooms, mulberry storage rooms, mounting rooms, equipments and rearing premises
should be thoroughly disinfected before brushing. The eggs should beessentially surface
disinfected. Silkworms should be reared under strict hygienic conditions. During rearing
the diseased and dead larvae form the major source of infection with the largest
 quantity of fresh Figure. 6. Dusting of “Reshamkeet Oushadh" polyhedral available.
Hence, the diseased larvae should be removed carefully without breaking the skin and
disposed suitably by putting them in lime vatsorbyburning. Dependingupon
thestageofsilkworm, suitable temperatureand humidityshould be provided. During IV
and V instars fresh air circulation should be ensured by providing cross ventilation. The
silkworms should be fed with nutritively rich mulberry leafand during later stages
feeding of tenderleafshould be avoided. Depending upon the stage of larvae, optimum
spacing and required quantum of leaf should be given. Proper bed drying is
necessarybeforeeachfeed toavoid accumulationof moisture in the bed. In addition to
the above, use of certain bed disinfectants could also prevent secondary contamination
and spread of the disease. Paraformaldehyde compounds are known to have anti-
microbial properties and various formulations involving this chemical have been
prepared like Papazol in Japan and ReshamkeetOushadh in India. The latter is a bed
disinfectant formulation containing 1 per cent captan (N-Trichloromythyl Thio-4-
Cyclohexane 1,2Dicarboxymide), 1percentparaformaldehyde(Trioxymethylene) 2
percent Benzoic acid and 96 percent slaked lime powder giving dual protection against
grasserieand muscardine. It shouldbedustedonthe larvae and bedwith thehelpofathin
cloth at the rate of2-3 grams/0.1 sqm. area during early instars and 45 grams.0.1 sqm.
during IV and V instars. The dusting should be done preferably once after each moult,
halfan hourbefore resumption offeed. An additional dustingshould be doneonthe4th
day offinal instar afterbedcleaning. Thedustingshould not be done when the larvae are
under moult or preparing for moult. The quantity of Reshamkeet Oushadh required for
100 disease free laying (40,000 larvae) is between 3-3.5 kgs.

1.2 Cytoplasmic polyhedrosis

Cytoplasmic polyhedrosis is one of the major viral diseases found during summer.
Causes ofthe disease This disease is caused by Smithia virus belonging to thesub-
group type I ofthe family Reoviridae. The virus is spherical 60-70 nm in size. It infects
and forms polyhedral mainly in the cell cytoplasm ofthe midgut cylindrical cells.
When the cylindrical cells are completely infected the virus switches its infection and
forms polyhedral even in goblet and regenerativecells. The infection in the
midgutstarts from the posterior portion and slowly proceeds towards theanterior
portion. The polyhedral variesgreatlyin size from 1-10μ. The shape is usually
tetragonal or hexagonal but rarely trigon. Infectionusually takes place through the
feeding ofpolyhedral contaminated mulberryleaf. Heat, cold and chemical treatment
have also been found to induce this disease. The major factor influencing the
outbreak ofthis disease is the inferior quality of mulberry leaf, high temperature and
fluctuations in temperature and humidity. The major source of contamination and
spread is the rearing bed itselfas thevirus with the polyhedral are excreted along
with the faecal matter. Cytoplasmic polyhedrosis virusaffectedlarvae (early stage).
 Symptoms: Generally cytoplasmic polyhedrosis virus infects larvae, but rarely pupae
and adults. Affected larvae show symptoms of slow growth, stunted body, reduced
mulberry consumption and dull white colour. Individual sizes vary great and the
worms show delayed moulting. Ifinfection takes place in grown-up larvae, the thorax
becomes transparent and the body atrophies. As the disease develops, the milky-
white portion advances rostrally until the entire gut becomes chalky white giving the
body of the worm a milky white colour (Fig. 8). At this stage larvae excrete soft
whitish faecal matter containing numerous polyhedral. Occasionally the anal region
is soiled with rectal protrusion. If the affected larvae are dissected the midgut is
seen as whitish and opaque compared to the greenish and transparent mid gut of
the healthy larvae.

Prevention and control: The cytoplasmic polyhedral virus, occluded in the

polyhedral can persist for more than one year inside the rearing room, appliances
and surroundings. Their resistance to formalin is greater than nuclear polyhedral.
Hence the rearing room, appliances and surroundings should be thoroughly
disinfected by using a 2 per cent formalin solution with 0.5 per cent freshly prepared
slaked lime. The infected larvae, faecal matter and bed refuse should be completely
destroyed either by burning or by decomposition in a manure pit. Care should be
taken to rear silkworms under proper temperature, humidity and hygienic
conditions. On appearance of the disease, trays, seat paper, nets and foam pads
should be replaced with disinfected ones. Mulberrygrown undershade, in
phosphorous deficient, high acidic and alkaline soil conditions produce poorquality
leaves. Feedingofsuch leaves has often been found to induce cytoplasmic
polyhedrosis and hence should be avoided. Chemicals such as 1 per cent calcium
hydroxide can be sprayed on the mulberry leafand fed to larvae to reduce the
occurrence of cytoplasmic polyhedrosis. Some interferon producing chemicals like
Poly.I:c, 2', 5'-oligo (A) have been reported to inhibit the growth of cytoplasmic
polyhedrosis virus (CPV) in the silkworms but they are yet to be introduced in the
field for commercial use.

1.3 Infectious flacherie

It is a highly contageous and exceedingly disastrous disease found in all the silkworm
rearing areas of the world.

Causes of the disease: This disease is caused by a non-occluded Morator virus

belonging to the family Picornaviridae. The virus is globular and measures 24-28 nm.
Infection usually takes place perorally. During the invasion of the midgut, the virus
preferablyinfects thegobletcells. As theinfection advances the virus is dispersed in
the lumen of the digestive tract and excreted with the faeces. 49 Unlike the
cytoplasmic polyhedrosis the infection starts from the anterior region of the midgut
and progresses toward the posterior region and never exhibits the chalky white
appearance.
 Symptoms: Symptoms are similar to bacterial flacherie, such as loss ofappetite,
transparent cephalothorax, shrinkage ofthe body, retarded growth and empty
foregut. This follows vomiting ofgastric juice and diarrhoea. The midgut is emptywith
little mulberry leafbutfullofyellowish-brown fluid. Thediagnosisofthisdiseaseis not
possible from external appearance nor through ordinary microscopy but can
bedetected by fluorescent antibody technique or by staining the infected cells with
pyronine methyl green. Latex agglutination and other serological tests are also being
used now for the detection of this disease.

Prevention andcontrol: As the virus exhibits high virulence and may retain its
pathogenicity in the body of the dead worms for 2-3 years, the rearing rooms,
appliances and surroundings must be thoroughly disinfected by using 2 per cent
formalin and 0.5 percent calcium hydroxide or bleaching powder containing 1 per
cent active chlorine in it. Silkworm rearingunderoptimum climaticandhygienic
conditions and better feed management helps in the reduction in the incidence
ofthe disease. As the disease spreads from the virus excreted along with the faeces,
the diseased larvae with bed refuse should be burnt or put in a manure pit for
thorough decomposition. Onlycorrectivemeasureknownfor this disease is the testing
of the chawki reared worms for an early detection of the disease through
fluorescent antibody, agar gel diffusion, immune-electrophoresis and
seroagglutination and rejection of the infected batches.

1.4 Densonucleosis
This is a viral flacherie disease more recently reported from Japan (1973). Initially it
was named as Ina-Flacheirevirus (Ina-F.V.) being found first in thesuburbs ofthe Ina
city in the Nagano prefecture. Following that several investigators studied it in detail
and concluded in common that the virus was different from the earlierknown
IFVbutquiteclose to the densonucleosis virus ofthe wax moth, G mellonella and the
new disease was named as Bombyx densonucleosis.

Causes ofthe disease: The disease is caused by a non-occludedvirus belonging to

thegenus Densovirus of the family Parvoviridae. The virus particles are globular with
a diameter of20 nm. Infection usually take place orally. The major source of cross
contamination is the virus excreted alongwith the faeces by thesilkworm and the
pyrallidmoth frequenting the mulberry field which is also known to be a harbour of
the disease.

Symptoms: Retardation ofgrowth and shrinkage of body take place in the injected
worms. Body flaccidity like flacherie infected worms is the other major symptom
ofthe disease. On dissection, alimentary canal of the diseased larva appears pale
yellow in colour without most ofthe content. Thissignis quite similar to that in
thecaseofIFVinfectionbutonemajordifference observed from the histological study is
that while the IFV invades the goblet cells of the midgut this virus multiplies in the
nuclei of the columnar cells. This was also confirmed through the fluorescent
 antibodytechnique. When thesilkworm larvae were per-orally infected with Bombyx
densonucleosis virus (DNV) they usually died after seven days showing the flaccidity
as the major symptom. Prevention and control: Epizootiological investigations with
DNV have shown it to be present in the rearing rooms and in the dusts on mulberry
leaves from the field having pyrallid moths with this infection. The virus has been
found to be highly thermolabile andwhen thelarvae reared at 25-28°C were
transferred to a temperature of 37°C the multiplication oftheviruswas greatly
reduced. Susceptibility to DNV was also found to be genetically controlled with some
varieties and crosses being non-susceptible to the disease. Effective methods of
prevention and control ofthis disease may thus be the stoppage ofcross-infection,
early detection and rejection of the batches found to be infectwith thevirus through
fluorescent antibody studies and rearing of the non-susceptible breeds/crosses.

1.5 Comparison of different virus diseases of silkworm

In the preceding pages, the causes, symptoms, routes of infection, course of the
disease etc. of different virus diseases of silkworm have been described individually.

2. Bacterial diseases
Bacterial diseases affecting silkworm are collectively known as flacherie due to the
flaccid nature of the diseased larvae. The incidence of flacherie is high during hot and
humid seasons. In general, massive out-breakofthesediseases are uncommon but
depending upon poordisinfection, accumulation offaeces in the rearing trays, feeding of
mulberry leaveswithcontamination, improperhandling and unsafe use of bacterial
pesticides, large scale loss in crops sometimes occur. Bacterial diseases of silkworms are
divided into three major types namely bacterial septicemia, bacterial diseases of the
digestive tract and bacterial toxicosis.

2.1 Septicemia
This is a condition where bacteria multiply enormously in the blood (haemolymph)
of the larvae, pupae and moths. Septicemiaduring the larval stage leads to larval
mortality whereas the infection in pupal and moth stages leads to a large number of
melted cocoons affecting the egg production in the grainages.

Causes ofthe disease: This disease is caused by the multiplication of a large number
of bacteria, bacilli, streptococci and staphylococci in the haemolymph. The route
ofinfection is through injury or wounds and rarely perorally. Two major types of
bacterial septicemia are generally observed, one is the black thoraxsepticemia
caused by Bacillus sp. belonging to the family Bacillaceae of the order Eubacteriales
size 1-1.5 x 3 microns, spores subterminal, gram-positive and the other is the red
septicemia or serratiasepticemia caused by the bacillus Se,ratia marcescens Bizio
size 0.6-1.0 x 0.5 microns non-sporulating and gram negative. The former is more
resistant to disinfectants than the latter except for lime emulsion.
 Symptoms: They have some common symptoms like sluggish movement, decreased
appetite, straightened body, swollen thorax, shrinkage of abdominal segments,
vomiting and bead like faecesand loss ofclasping power oflegs. Further, the body
becomes soft and discoloured and the body wall ruptures easily emiting foul
smelling fluid. Difference in the symptoms of two diseases are that, in case of the
black thorax septicemia, the blackening starts from the thorax and extends to the
dorsal vessel till the whole body blackens and rots whereas in the latter case the
whole body softens taking a slightly reddish tinge. Septicemias aregenerally acute
diseases,spreading quickly, the time elapsing from the time ofinfection to death at
28°C being about 10 hours. At higher temperature and under epidemic conditions
they may die within 5-6 hours.

Prevention and control: High temperature and humidity conditions are most
favourable to the propagation of the bacteria responsible for these diseases and so
these diseases occur chiefly in the seasons having high temperature and humidity.
They normally follow wound infection. The bacteria enters generally through the
wound and multiplies in the haemolymph, disrupting the normal physiological
functions, causingsepticemia. Thethins tar larvae are more prone to injury and these
diseases thus occur mostly in the later part ofthis stage. An effective means of
control of these diseases can be the maintenance of hygienic condition so that these
bacteria do not occur on the mulberry leaves, in the rearing room and rearing
equipment. Care should be taken to avoid injury to the worms, overcrowding of
trays and accumulation of faeces in the rearing bed.

2.2 Bacterial disease of the digestive tract

This disease is otherwise known as transparent head disease due to the bacterial
multiplication in the digestive tract leading to the swelling and transparency of the
head.

Causes of the disease: The causative agent ofthediseaseis non-specific.

Howeverthecommon bacteriumseenassociatedwiththisdiseaseisagram positive
Streptococcus sp. belonging to the family Streptococceae. The bacteria are round
0.7-0.9 microns insize andarefoundjoinedby group oftwo or more to give a beaded
appearance. Besides the streptococcus sp. Someshort bacilli and large bacilli have
also been found to occur in the digestive tract eliciting the disease. Under poor
nourishment and adverse environmental and rearing conditions, the physiological
function of the digestive tract is disturbed. As a result, the bacteria devoured along
with mulberry leaf multiply in largenumber and destroy the membraneous tissues.

Symptoms: General symptoms are poor appetite, sluggish movement, transparent

head, stunted body size and retarded growth sometimes with oral and anal
discharges. The sick worm soften hide under the mulberry leaves. Incase
ofalatestageattackbythediseasethewormsremain in the spinning tray for a long
period without spinning cocoons till they die.
 Prevention and control: Feeding of proper type of nutritious leaf, maintenance
ofrequired temperature and humidity conditions, maintenance
ofhygienicconditioninrearingbeds andcullingoutof the diseased worms may prevent
and reduce the disease occurrence to a considerable extent. Since this is anenteric
disease, addition of chloramphenicol to the diet has beenfound to bringconsiderable
improvement.
2.3 Sotto
This is otherwise known as bacterial toxicosis. This happens when the silkworms
come in contact with the toxin producing bacilli.
Causes ofthe disease: This disease is caused by different strains of
Bacillusthuringiensis belonging to family Bacillaceae of the order Eubacteriales. The
sotto bacterium has a vegetative, cytocyst and spore form. The spore produces delta
endotoxin. Infection is usually peroral but can also take place through wounds or
injury. After entry into the silkworm bodythe toxiccrystals aredissolved in the
alkaline gut juice and are absorbed through the gastricwall affecting the nervous
system, leading to spasm and paralysis. Symptoms: Infected larvae lose appetite
suddenlyandshowthesymptoms ofconvulsions, lifting ofhead, spasm, tremors,
paralysis, distress, suddencollapseand death. Shortly after death the corpse is out-
streched, hard to touch and the head appears hook shaped. The body turns
gradually to brown, blackish brown and black and rot exuding foul smelling dark
brown fluid.

Prevention and control: Besides conducting initial

thoroughdisinfectionoftherearingroomand equipment to eliminatethe bacteria, care
should be taken to see that this bacteria does not get entry into the rearing room
and rearing beds. Various strains of Bacillus thuringiensis are being produced now
commercially as biological insecticides for the control of insect pests including
mosquitoes. Their toxicity against silkworm should be assessed and strict care
should be taken to see that the strains toxic to silkwormare not used in the silkworm
growing areas.

3. Fungal diseases

Fungal diseases otherwise called mycosis, is caused in the silkworm by a fewparasitic

fungi. Two major kinds of such disease are Muscardine and Aspergillosis. Muscardine
appears in various forms and depending upon the colour of spores which cover the body
ofthe silkworm giving a characteristic colour, they have been named as white-
muscardine, green-muscardine, yellow-muscardine, black-muscardine, red-muscardine
etc. The more common muscardine diseases are, however, white and green-
muscardine. In addition Aspergillosis is also found to occur. Since the silkworm attacked
by a fungal disease in course of time turns hard and chalky, muscardine disease is also
called Calcino.
3.1 White muscardine
It is the most common and widely prevalent fungal disease found in all sericultural
countries. This disease occurs usually during rainy and winter seasons under
moderate to low temperature and high humidity conditions.

Causes of the disease: This disease is caused by different species ofBeauveria

ofwhich the most virulent is Beauveria bassiana (Balsamo) Vuillemin. This fungus
belong to the family Moniliaceae, order Moniliales of class Fungi imperfecti.
Infection is mainly by body contact, rarely through wounds and not by ingestion.
Main sources ofinfection are the mummified larvae, infected seat paper, tray and
dead wild lepidopterous larvae from the mulberry field. The disease is highly
contageous as the conidia are air borne. The developmental cycle of Beauveria
bassiana consists of three dinstinct stages namely conidium, vegetative mycelium
and aerial mycelium. The conidium is colourless, globular or rarely oval in shape and
porcelain white when gathered in a mass. Under favourable conditions of
temperature and humidity the conidium germinates within 8-10 hours ofcoming in
contact with the body of silkworm. On germination the conidium not only sends out
its germ tube but also secretes chitinase which facilitates the germ tube to
penetrate the body wall for furthermultiplication. Thegerminating tube ofthe
conidium after invading the blood of the larvae develops into vegetative hypae.
Atthe tip of the hyphae round or oval shaped short hyphae develops. These often
detach themselves and elongate to form vegetative hyphae.
The vegetative hyphae comes out of the skin to form aerial hyphae bearing
innumerable conidiophores. Theseconidiophoresgive rise to small branches which
bear one or two conidia.

Symptoms: At the early stage of infection symptoms are not distinct, but as the
disease advances, moist specks appear on the skin. At this stage, larvaelose
appetiteand becomeinactive. The body of the larvae becomes limp, loses its skin
elasticity, stops movement and finally they die. Before death, symptoms ofdiarrhoea
and vomiting appear. After death, the body is initially soft, but within 6-8 hours it
becomes stiff and hard. Atthis stage the body is pink in colour. Thisisdue to the
multiplication ofSerratia marcescens, a secondary bacterium. One to two days later,
wooly aerial hyphae grow out between intersegmental membrane. Subsequently
the whole body is covered with white powdery conidia except the chitinous parts
ofthe head. The larvae, unlike other diseases do not rot or decay but remain hard as
the fungus secretes double oxalate -crystals of ammonium and magnesium.
In case of pupal infection the pupae slowdown their reaction to outsidestimuli. The
thoraxshrinks and abdomen is wrinkled. The aerial hyphae and conidia grow up to
one third of its ordinary weight inside the cocoons. Such cocoons sound like dried
cocoons when shaken. During moth stage the body is hardened and the wings fall
ofeasily.
Prevention and control: Before the commencement ofsilkworm rearing, rooms,
appliances and rearing surroundings must be thoroughly disinfected with 2 percent
formalin or 5 per cent bleaching powdersolution. This disease can bekept under
checkbyavoidinglowtemperatureandhighhumidity during rearing as they are more
ideal for fungal growth. The rearingbed should as much as possible be kept thin and
dry in order to avoid the germination ofconidia and spread of the fungus. If the
disease is found during rearing, the trays, seat papers, cleaning nets, foam pads etc.,
must be disinfected and replaced. Diseased worms should be removed carefully
before they get mummified and should be placed in lime jars or destroyed by
burning or deep burying, with a disinfectantspray.

Similarly the bed refuse along with the faeces should be disposed of properly.
Mulberry pests in the garden should be controlledas theygeteasilyinfectedwith this
pathogen, later becoming an important source for cross contamination to the
silkworm. In addition to the above, anti-muscardine powders can be fruitfully used
to control the outbreak and spread of this disease. A few methods of application of
the same are given below: Application offormalin chaff: In this method formalin
solution of required concentration depending on the silkworm instar is mixed with
burnt paddy husk and sprinkled on the larval body and bed. The concentration of
formalin required is 0.4 per cent during I and II in. stars,0.5 percentin IIIinstar, 0.6
percentin IVinstar and 0.8 per cent during V instar. The paddy husk is charred or
burnt either by burning or roasting in a panwithoutmakingash. Dependingon
theinstarof larvae, the required strength of formalin is mixed with the burnt paddy
husk in the ratio of 1:10 by volume and mixed thoroughly. Then it is sprinkled evenly
on the larvae and covered with a paraffin or double fold newspaper.

After 1/2anhourthepaper cover is removed and feed is given. Formalin chaff

application should not be done when larvae are preparingfor moultorunder moult.
Applicationof formalin chaff can be done before brushing on the newly hatched
larvae and after each moult 1/2 an hour before the resumption of feeding. The
frequency of application of formalin chaff should be increased depending on the
incidence ofdisease. Application of Dithane M 45(Zinc ion Manganese ethylene oxide
bisdithiocarbomate) or captan (N-Trichloromethyl Thio-4-Cyclohexane 1,2-
Dicarboximide) These are the two commonly available fungicides used for the
control of muscardine. These fungicides are used at a concentrationof 1 per cent
during, I, II andIII instars and 2 percent during IV and V ins tars in combination with
levigated Chinaclay or Kaolin. The ingredients are thoroughly mixed and tied in a thin
cloth and dusted on newly born larvae and after each moult 1/2 an hour before the
resumptionoffeed. Anadditionaldustingshouldbe done on the 4th day of final instar
after bed cleaning. The quantity required is 2-3 grams per0.1 sqm. AreaduringI, IIand
IIIinstars and 4-5 grams during IV and V instars. The dustings should not be done
when the larvae are preparing for moult or are under moult.

The dusting frequency should be increased ifthe intensity ofinfection is high.

Application of "Reshamkeet Oushadh" It is a bed disinfectant formulation used to
prevent both muscardine and grasserie. Its constitution, method of application and
 quantity required has already been indicated in the part covering the control of
grasserie disease.

3.2 Green muscardine

This disease occurs during autumn, late autumn and winter season.
Causes of the disease: This disease is caused by Nomuraearileyi Farlow, belonging to
family Moniliaceae of class Fungi imperfecti. Infection takes place through skin by
Conidia. They germinate in 15-20 hours in favourable conditions. The major source
of cross contamination is the dead mummified larvae and infected wild
lepidopterous insects from field. The three growth stages of this pathogen are
similar to white muscardine comprising the conidium, vegetative mycelium and
aerial mycelium.
The conidium is oval in shape and slightly pointed at one end. It is light green and
single celled. Germinates at 22-24°C in 20 hours.
The vegetative mycelelum has a germinating tube which elongates and gives rise to
fine and filamentous mycelia with septae. They in turn produce large amount of
colourless tubular or bean shaped hyphae. Vegetative mycelia become clustered
with hyphae which in turn form conidiophores. These conidiophores are wheel
shaped and unbranched. Conidiophores bear few or several gourd shaped
sterigmata each ofwhich carries at the tip a chain of conidia.

Symptoms:During early period of disease no noticeable symptoms are seen. As the

disease progresses dark brown irregular lesions appear on the ventral, dorsal and
lateral sides. These lesions sometimes gather into large spots with clear
circumference. In a serious case the silkworm vomits fluid, has diarrhoea and dies.
After death thecorpseis soft initially and gradually hardens. Two to three days after
death mycelia appear from the inter segmental membranes and spiracles. Gradually
the whole body is covered with whitemycelia. After 10-15 days these mycelia are
covered with fresh green conidia.

Prevention and control: Prevention and control measures are similar to those
recommended the white muscardine.

3.3 Aspergillosis
This is a menacetoyounginstar larvaepartietlarlywhen high humidity is prevalent.

Causes of the disease: This is caused by different species of Aspergillus and

Sterigmatocytis belonging to the family Moniliaceae of class; Fungi imperfecti. About
one dozen species are reported to infect silkworms of which Aspergillu: flavus link
and Aspergillus oryzae Wehmer are most common. The growth stages of the
pathogen consist of the conidium, vegetative hyphae and aeria hyphae.
The conidium is spherical, 3-7 μ in size. They are fairly resistant to environmental
factors and formalin treatment. The favourable temperature for
germinationofconidia is 30-35°C. Conidia after germination invade the body of the
 silkworm and develop into vegetative hyphae without the formation of short hyphae
and they grow only at the site of invasion. The conidiphore is thick and at the distal
end expands into a globular or oval structure bearing one to two rows ofradiating
sterigmata on which conidia are formed.

Symptoms: This disease pathogen infects mainly first and second instar silkworms
but it is not strong enough to affect grown up larvae. Infected larvae cease eating
mulberry leaf, become lethargic, show body tension, lustrousness and then die. Just
before death the head and thorax is extended outwards and vomiting occurs.
Oneday after death aerial hyphae appear and later conidia cover the body. The
colour depends on the type of pathogen. The hardening of corpse in dead larvae is
limited to the site of fungus penetration and other parts become black and rotten.

Prevention and control: They are basically similar to white muscardine. As the main
source of pathogen is through mouldy objects, special care should be taken to
bake/sundrytherearingtraysand utensils. For disinfection purpose 4 per cent
pentachlorophenol may be used instead of formalin.

4. Protozoan diseases
Protozoa which are injurious to silkworm are the parasitic ones belonging to the class
Microsporidia and genera Nosema, Pleistophora and Thelohania. Besides these,
Trypanosoma and Leptomonas have also been reported to infect the silkworm
Bombyxmori_L. However, the major protozoan disease of the silkworm is the pebrine
disease, so named due to the appearance of black peppery patches following infection.

4.1 Pebrine
Pebrine is a chronic and disastrous disease of the silkworm Bombyx mori L. It was
this disease which was responsible for the sudden collapse of the silkworm industry
of both France and Italy in 1965. Even though the fight against this disease in all the
sericultural countries is going on since more than 100 years, the disease is not yet
eliminated. However, it has been kept under check by following the techniques of
strict mother moth examination for the supply of disease free silkworm eggs, in
addition to disinfection and hygienic rearings. Though the disease is under
reasonable control, it appears sporadically due to infected seed and persisting
secondary contamination in the rearing house.

Causes of the disease: Pebrine is caused by Nose ma bombycis N ageli belonging to

family Nosematidae of order Microsporidia. The pathogen infects the host through
feeding of contaminated mulberry leaf (peros) and also by rearing infected silkworm
eggs (transovarial). In addition to Nosema bombycis, seven different microsporidians
belonging to genera Nosema, Pleistophora and Thelohania have been reported to
infect the silkworm. These microsporidians differ in their spore morphology, target
tissue and virulence. They have been tentatively designated as M 11, M 12 and M 14
(Nosema sp.), M24, M25 andM27 (Pleistophorasp.) and M 32 (Thelohaniasp. ).
However, these microsporidiaans differ from Nosema bombycis in that they do not
infect silkworm transovarially. So, they are harboured in wild lepidopterans and
constantly introduced into silkworm rearing, leading to cross contamination.
Sources of infection are rather extensive. The main source is the rearing of
transovariaily and surface contaminated layings. Infection also results from diseased
and dead larvae, faeces of larvae, moths, diseased egg shells, larval and pupal
exuviae etc. In the rearing bed major source of infection is the faeces of diseased
larvae, contaminated tray, seat paper and dust from infected rearing and leaf
storage rooms. Sometimes infection takes place through contaminated mulberry
leaf from field. The excreta and dead larvae of pebrine infected wild insects may also
form a source of infection. The life cycle of Nosema bombycis N ageli includes three
stages namely, spore, planont and meront.
The mature spore is oval or ovocylindrical. It measures approximately 3 -4 x 1.5 - 2.5
µ with three layered membrane: the inner, middle and outer. The sporoplasm is
stretched in the form of girdle across the width of the spore and it contains a pair of
nuclei. The spore has a polar capsule and polar filament. The polar filament is given
out on treatment with a number of chemicals like H 202 and Kcl. Spores are highly
refractive and appears light blue under the microscope. The spore represents the
dormant stage of the pathogen and can survive in the ordinary conditions of rearing
house for more than a year. It retains its infectivity even after three years in the
dried body of the female moth, in liquid medium for more than 3 weeks and in soil
for more than 2 months. But the spore is susceptible to dessication and cannot
survive for more than 6 - 7 hours in direct sunlight (39 - 40°C). It is also weak against
heat, chemicals and disinfectants. Pebrine spores When live spores enter into the
silkworm through mulberry leaf, they germinate in the gut due to high alkalinity and
potassium ions. As a result the polar filament is extruded and the sporoplasm along
with two nuclei creeps through it and injects into the midgut tissues. Subsequently
the polar filament gets digested in the alimentary tract. The two nuclei of the
sporoplasm unite to form a uninucleate planont. The planont measures 0.5 - 1.5 µ
and is formed in 1- 2 days. The planont is sub-globular with a strong refractive
nucleus without shell, performs amoeboid movement and reproduces by binary
fission. The planont which intially infects the gut later passes through the gut wall
and invades the various susceptible tissues.
Once the planont penetrates the host cell, it transforms into a sedentary form and
becomes localized. This stage is known as meront. Meront is an intracellular stage
and has a definite cell wall which absorbs nutrients from host cell. The meront is
spherical or pear shaped and is formed in 2 - 3 days after infection. It reproduces by
binary fission, multiple fission or by budding. When Cytoplasm of the host cell is
exhausted, meronts are arranged in parallel rows.
The meront after massive proliferation fills up the host cells and when nutrients are
depleted, sporulation takes place. From the germination of the spores to sporulation
is the entire developmental cycle of the pebrine protozoan.
Symptoms: The symptoms of this disease can be observed in all the stages of
silkworm viz., egg, larvae, pupa and adult. These symptoms form an important
criteria for identifying the disease.
In the egg stage, poor egg number, lackofadequate adherence to the substratum,
lack of egg uniformity, more of unfertilized and dead eggs, poor and irregular
hatching are some of the symptoms. Sometimes infected eggs cannot hatch out and
hatched larvae may also die.

Larvae show poor appetite, retarded growth and development leading to un-
uniformity in size. Larvae moult irregularly and show sluggishness. Transovarially
infected larvae die beforethird moult but those which are heavily infected die during first
instar itself. The larval body shows wrinkled skin with rustic brown colour and in the
moribund stage they do not rot but remain rubbery. The affected gut becomes opaque and
the silkgland shows white pustules in different places along its length. Sometimes black
irregular pepper like spots are noticed on larval skin.

The infected pupae are flabby and swollen with lusture less and softened abdomen.
Sometimes irregular black spots are noticed near the rudiments of the wing and
abdominal area. Highly infected pupae fail to metamorphose into adults. The moth
emergence is delayed and improper. They have clubbed wings with distorted
antennae and do not mate properly. The scales from wings and abdominal area
easily come off. In infected moths if the accessory glands are infected the moth may
lay eggs with less gluey substance resulting in their detachment from the egg cards.

Prevention and control: The fundamental measure for the prevention and control of
this disease is to produce healthy eggs, so as to avoid embryonic infection. This can
be achieved by conducting systematic mother moth examination. The other
methods are to conduct effective disinfection of rearing rooms, equipments and
surroundings and maintenance of strict hygienic conditions during rearing. It is
essential to surface disinfect the layings in 2 percent formalin for O minutes before
incubation. Such surface disinfection though practiced in grainages should be
repeated again after release from cold storage as also by farmers. If the eggs are in
advanced stage of embryonic development surface disinfection is done with 1 per
cent formalin for 5 minutes. The room and equipments must be washed and
disinfected before incubation.

Young silkworms should be reared under hygienic conditions. As a precaution test

examination of unhatched blue eggs, dead eggs, hatched larvae and eggshells can be
done and if pebrine is detected, such eggs should not be brushed and if brushed the
larvae should be destroyed. Similarly predictive examination could be conducted by
utilizing unequal larvae, late moulters, faceal matter and exuviae for the detection of
pebrinespores. These tests may not only minimise the chances of rearing
transovarially infected layings, but also check cross contamination and spread of the
disease. Infected silkworms, faeces and mulberry field pests are important sources
 of infection and should be properly disposed of to prevent cross infection and
spread of the disease.

During seed production in addition to mother moth examination, care should be

taken to prevent contamination from other sources. The equipments used forone lot
should not be used for the other till they have been thoroughly cleaned and
disinfected. Eggs after surface disinfection should be dried and stored in a separate
room away from egg production and examination room.

Besides, the above preventive/corrective measures, it has been reported that

immersing of the silkworm eggs in hot water, high temperature treatment of the
pupae, dipping of the eggs in hot hydrochloric acid minimise the incidence of
pebrine. Chemotherapy of Nose ma infection has been reported through a number
of antimicrosporidian drugs like fumagillin, benomyl, bengard, bavistin, ethyl and
methyl thiophanate and some of their analogues with positive results, but
preventive methods have always been found to be better than the curative
measures.

5. Other miscellaneous diseases

These are non-infectious diseases caused mainly due to poisoning by agricultural
chemicals and factory exhaust gases. These poisonous substances gain entry into
silkworms through feeding, body contact etc.

5.1 Poisoning from agricultural chemicals

Causative agents: The most important agricultural chemicals poisonous to silkworm

are organophosphorus, organochlorine, organonitrogen and pesticides of plant
origin. Among these both organo-phosphorus and organochlorine insecticides can
inflict acute poisoning. Organophosphorus compounds are known to inhibit
chalorinesterases by poisoning the ganglion whereas organochlorine is an axonic
poison affecting the sensory neurons. The other two agricultural chemicals like
organonitrogen and insecticides of plant origin cause death but in mild cases they
lead to the spinning of deformed or flimsy cocoons.

Symptoms: Symptoms due to poisoning by agricultural chemicals are similar. They

include slight excitement, swinging of anterior half of the body, enlargement of
thoracic region, erratic movement. These are followed by vomiting of the digestive
juice, lying on the side, shortening of the body due to loss of digestive juice, muscle
contraction, paralysis and finally death.
Prevention and control: The main preventive measure can be the avoidance of
contamination of mulberry leaf by these insecticides. While spraying agricultural
chemicals one should pay special attention to the direction of wind so as to avoid
contamination to the mulberry leaf. If insecticides are sprayed on mulberry garden
 for the control of diseases and pests, safety periods should be followed for leaf
harvest. During rearing if chemical poisoning occurs to silkworms, cross ventilation
should be ensured for free circulation of fresh air. If needed, the worms may be
dipped in cold water for a brief period and them reared in a cool well ventilated
room with the supply of fresh mulberry leaves. All equipments and utensils that
have come in contact with the insecticides should be thoroughly cleaned and
washed with alkaline solution before re-use.

5.2 Poisoning by factory exhaust gases

Feeding silkworms with mulberry leaf contaminated from the factory exhaust gases
like sulphur dioxide, hydrogen fluoride and chlorinealso induces poisonous effect.

Symptoms: The main symptoms are slow and uneven growth resulting in the
disparity of the larval development. If young ins tar larvae are affected, the body
atrophies, the thorax swells and the posterior part shrinks. In later instars larvae
haveband-likeorring-likedarkbrownlesionswhich are frequently found near the
intersegmental membranes. These lesions burst easily and release light yellow fluid.

Prevention and control: The factories involved in the production and release of
these gases should be located at least one km. away from the mulberry fields. If
mulberry leaves are contaminated with these gases, they should be washed in
calcium hydroxide to reduce the degree of damage to silkworms. If silkworms are
found to be poisoned they should be supplemented with fresh good quality
mulberry leaves, so that they may recover from the poisoning effect.

6. Integrated control of silkworm diseases

What have been described so long are the diseases in an individual manner with
methods for their prevention and control. But it has to be understood that the
protection is required not against any, but all the diseases. It has to be further
understood that it is not only the presence of the pathogen that causes the disease,
there are many other factors, biotic and abiotic which are directly and indirectly
responsible for the initiation and spread of the diseases. So, to have a real control of the
diseases and protection of the cocoon crop, one should rather adopt an integrated
approach taking into consideration all the factors which lead to the initiation and spread
of the diseases. Some of them are discussed below:

(i) Use of disease resistant varieties of silkworm

The prevention and control of silkworm diseases should start with the selection
of disease resistant varieties. Different varieties and breeds of silkworm are
known to have differential resistance against different diseases, temperature
and humidity conditions as well as the condition of mulberry leaf. Depending
upon these factors, while planning the rearing, the breeds/crosses to be reared
should be properly selected which could go a long way in harvesting a successful
crop.
(ii) The quarantine of the silkworm
Seed The silkworm seed to be reared should be disease free. Firstly, for pebrine-
freeness detection, mother moths should be thoroughly examined, followed by
the surface disinfection of eggs to see that the eggs taken for rearing are disease
free. As an additional step the unhatched larvae also could be tested for disease
freeness.

(iii) Improvement of disinfection

Proper disinfection is one of the key factors determining the success of rearing.
Besides the general disinfectants like formalin, there are a number 65 of other
disinfectants, known to be particularly effective against certain pathogens like
lime against C.P.V., chlorine against bacteria. So, while choosing the
disinfectants, the prevalence and likely incidence of a disease should be taken
into consideration and depending on that the disinfection should be done either
through a combination of chemicals or in succession with more than one
disinfectant. The method and concentration to be used should also be properly
taken care of.

(iv) Maintenance of hygienic condition during rearing

Besides the initial examination of eggs, their disinfection, disinfection of rearing
rooms and equipments being carried out to remove the primary source of
infection, adequate care should be taken to
preventsecondaryorcrossinfectionduringrearing. To achieve that, strict hygienic
condition should be maintained during rearing in the rearing room and the
rearing bed and, ifnecessary, bed disinfectants should be used.

(v) Use of appropriate rearing room and equipment

Rearing room and equipment used have also bearings on disease incidence. A
well ventilated house and a house where temperature and humidity can be
controlled can always improve the health of the silkworm and reduce the
incidence of diseases. Equipmenl used like proper type of stands, trays, seat
paper and the bed-cleaning nets also help in the maintenance of hygienic
condition and a consequent reduction and a consequent reduction in the
incidence of diseases.

(vi) Improvement of rearing technique

Silkworm rearing is very much affected by the hygro thermic condition of the
environment. Being a cold blooded animal it has little power to adjust against
the t1uctuations of temperature and humidity. Adverse climatic conditions thus
affect the physiology of the worm very much and lower the resistance against
the diseases. Such fluctuations of temperature are even known to induce certain
viral diseases.
 Feed is also a factor which affects the physiology and health of the silkworm very
much. The feeding of insufficient unsuitable and non-nutritive leaves often leads
to a high incidence of diseases as under certain infective conditions healthy
silkworms can tolerate a certain amount of germ load, whereas the weak
silkworms become easily susceptible even to a small germ load which is depicted
in the next page:
Handling of worms at maul t and spacing given in the rearing bed are also
important factors determining the health of the worm and consequently the
incidence and the spread of the diseases. The latter particularly acts in a
numberof ways restricting the food availability to the silkworm, changing the
micro-climate in the bed as well as increasing the chance of cross-infection.
These also need to be taken care of to check the incidence and spread of the
disease.

(vii) Physical treatments

A number of physical treatments like treating with hot water at different stages
have been known to kill certain pathogens and consequently control the disease.
Where, necessary and possible, such methods should be used.

(viii) Chemical treatments

Similarly, certain chemicals have been known to be effective in the prevention
and control of certain diseases. Those chemicals should also be used in a proper
manner, at appropriate time and at appropriate doses to prevent and control
those diseases.

(ix) Exploitation of immune response

Though it is a virgin field, information are coming out about the immune
response in silkworm. humeral and other, particularly through the production of
interferons as described elsewhere. An eye should be kept on such development
also and their use.

PESTS OF MULBERRY SILKWORM AND THEIR CONTROL

Besides being susceptible to different diseases, the silkworm, Bombyx mori L. is also attacked
by a number of pests. Among the insect pests that attack silkworm, the most formidable one is
a dipteran parasitoid, Exoristasorbillans Wiedemann, otherwise called the uzi fly.

1. MAJOR PEST
Uzi fly, Exoristasorbillam Wiedemann ( =F.xoristabombycis = Trichol.ygabombycis =
Tricholygasorbillam = Tachinasorbillam)
This parasitoid is a member of the Tribe Exoristini under the sub-family Goniinae
belonging to the family Tachinidae of the order Diptera. Presence has been Reported in
Bangladesh, China, Japan, India, South Korea, Thailand and Vzet Nam The incidence of
this fly is very high in the tropical sericultural region, viz. Bangladesh, Southern part of
China, India, Thailand and Viet Nam. The extent of damage ranges from 10-30 per cent.

(a) Life Cycle

Adults are blackish gray in colour. Male is longer in body length (about 12 mm) than
female (about 10 mm). The head is triangular in shape. On the dorsal side of the
thorax, there are four longitudinal black bands. The abdomen is conical. Of the
abdominal segments, the first one is black and the rest greyish-yellow. Lifespan of
adult flies varies with sex and season. Males survive for about 10-18 days. Females
live 2-3 days longer than the males. Survival period is least during summer months.

Male can be distinguished from the female by the presence of external genitalia
covered with brownish orange hairs on the ventral side of the abdominal tip. Lateral
regions of the abdomen are covered with bristles more dense in male than in female
and in the latter restricted mostly to last two segments. The width of the frons of
the male fly is narrower than that of the female one. Longitudinal lines on the
dorsum of the thorax of the male are more vivid than female. The pulvilli of male is
larger than female.

Adults exhibit a definite courtship behaviour. Males have no distinct orientation

posture towards the females and they strike the resting and walking females. Mating
strike by male is followed by agitated state of the female before the pair establishes
the successful genital contact. Premating period is about 4-6 hours. The adults are
polygamous. They mate 1-2 times and 3-7 times within 24 hours of the adult
emergence and in the entire life respectively. Mating generally takes place during
early morning or in the late evening. The duration of mating ranges between half an
hour to two and half hours. A minimum of one hour mating is required for full
fecundity and maximum hatchability. Mating is not a pre-requisite for egg deposition
since virgin female also lays unfertilized eggs.

Oviposition in both the mated and unmated females start 44-45 h after their
emergence. Female uzi fly approaches the host larvae and after repeated survey
settles down on the body of the host. At the time of releasing the eggs, the female
Oy bends her abdomen in such a way that the tip of her abdomen touches the host
integument. After releasing each of the egg the female fly withdraws its posture,
walks over the host body and similar steps are followed before releasing every
successive egg. Under normal condition, 1-2 eggs are laid per host larva. Flies
oviposit practically anywhere on the body of the host larva. However, least number
of eggs are laid on the ventral aspect of the body. This parassitoid prefers to lay eggs
on late age host larvae which are also larger in size. The oviposition on young instars
larvae depends on theagedistributionofhostlarvae population and the relative area
of the silkworm body.
A single mated female uzi fly lays about 300- 1,000 eggs overa period of about9-
25daysdepending upon the seasons. The fertilized eggs are laid throughout the life
span of the female. Initially the number of eggs laid are few. Gradually, it increases
to reach the peak between fourth and seventh day after adult eclosion.
Subsequently, a gradual decline takes place with advancing age of the females. Eggs
are macro type and creamy white in colour. The egg measures 0.45 - 0.56 mm in
length and 0.25 - 0.30 mm in width. They are oblonginshapeandhatchinabout2-
5daysafteroviposition depending upon the climatic condition. Once hatched, the
maggot penetrates into the body of the silkworm.

The young maggot hatches out of the eggshell through the operculum which
generally faces the silkworm body. The newly hatched maggot directly penetrates
into the silkworm body. On penetration a sheath surrounding each maggot is formed
by granulocytes and proliferating tissues at the site of the wound. The size of this
sheath keeps the pace with the growth of the maggot, becoming thicker and black in
colour, so as to discernible on the surface as black lesion or scar sometimes bearing
the attached egg shell.

Maggots pass through three instars. In the first two instars, they develop just below
the skin of the host body and in the final ins tar they leave this site and move into
the body cavity. Maggots of first and second ins tars areyellowish-whiteincolour and
measure 0.7-1.5 mm and about 2.75 mm in length respectively while the third instar
maggots arc creamy-white in colour and measure 1.3-1.6 cm in length.Maggots have
eleven body segments.

Thematuremaggots escape from the host body by piercing the integument by its
pro-thoracic hooks in about 5-8 days depending upon season and number of
maggots developing per host larva. They feed on various tissues of the silkworm
body and the host larva dies by the time the maggots are mature to escape out from
the host body.

The escaped mature maggots which are negatively photo tropic and positively
geotropic, pupate in about 10-20 h depending upon the season. Pupation takes
place in the darker area in and around the silkworm rearing house like corners,
crevices, silkworm rearing beds, cracks of the rearing stands or trays, below the
antwells or in the superficial layer of the soil. Maggots just before pupation become
motionless and the body shrinks. In certain areas where the temperature goes
below l0°C, this fly mostly passes the winter season in the pupal form.

Pupae areoblonginshapesomewhat oval anteriorly and round posteriorly. They are

light reddish brown to dark reddish brown in colour. Body segments are eleven in
number and measuring 0.9-1.2 cm in length and 0.4-0.6 cm in lateral width. Adults
emerge in about 10-12 days. The male adults always emerge out earlier than
females.
(b) Type of damage and symptoms
The silkworm larvae infested upto early fifth instar die before they reach the
spinning stage. If infestation takes place in the late fifth instar, the mature maggot
comes out by piercing the cocoon and thereby rendering the cocoons unfit for mass
reeling. Infested silkworms or pupae can be identified by the presence of black scar
on the part of the skin where the maggot penetrates into the body of the host
larvae. Sometimes, an egg shell is left behind in the centre of the black scar. At the
initial stage of infestation minute creamy white oval eggs smaller than pinhead are
observed on the skin of the larvae.

(c) Period of occurrence

The number of generations per year differs depending upon the climatic condition.
In arctic region, there are four to five generations, in temperate regions six to seven
generations and in tropical regions ten to fourteen generations. In tropical countries
it generally occurs throughout the year.

(d) Prevention and control

For the prevention of uzi fly, sanitary and 70 hygienic measures are of utmost
importance. Care should be taken first to see that uzi fly maggots do not get access
to the holes and crevices of the rearing room and the places around where from
they normally come out and perpetuate the life cycle. Care should be taken to see
that the early spinning cocoons, most of which are uzi infested are not mixed with
normal cocoons and are stifled to kill the uzi maggots inside them. While taking the
cocoons to the market it should be seen that uzi fly maggots do not come out and
spill on the way and further. In the market it should be seen that uzi fly maggots are
frequently sweeped and killed by putting them into hot water, formalin water or
kerosine/insecticide mixed water. As far asseed cocoon transportation is concerned
it should be seen that the uzi infested cocoons are not transported to uninfested
areas and are disposed off at the nearest possible point.

For further prevention and control of uzi fly an integrated approach involving
physical, chemical and biological control methods are suggested as follows:
(i) Physical:
Creation of a physical barrier by providing wiremesh in the doors and
windows of the rearing rooms or mosquito net curtains around the rearing
stands. These methods have been found to be quite effective in preventing
the uzi fly females from getting access to the silkworms and laying eggs on
them reducing the crop loss to a considerable extent. Care should be taken
to see that doors are not kept open and curtain covers are not disturbed. A
physical barrier can also be created between the uzi fly and the silkworm by
dusting levigated china clay on the body of the silkworm during mounting
which prevents theoviposition by the fly. Doses recommended are 3-4 g per
100 spinning larvae and per sq.ft. area of the spinning tray.
(ii) Chemical:
A commercial formulation uzicide containing 1 per cent of Benzoic acid has
been developed in India which kills the eggs of uzi fly when
appliedwithin48hofegglaying. This treatment has to be repeated on alternate
days. The dosage recommended is 7-8ml/sq.ft. area. A similar spray of 3 per
cent phenol has been suggested by Bangladesh for killing the eggs of uzi fly.

Chemical control of uzi fly has also been found to be effective through the
use (dusting) of diflubenzuron at 2.5 per cent, the diluent used being
levigated china clay. Maggots/pupae collected from the cocoon market when
treated with this material (covered with a dust layer 2.54 cm thick) give rise
to sterile adults which mate but are not able to produce off spring. While
treating, maggots/pupae should be spread in a single layeron a shallow tray
with 200 maggots/pupae per sq.ft. Release programme of such flies which
emerge from treated maggots/pupae could have a good impact on the
reduction of the uzi fly population.

Caution: Diflubenzuron should be handled with same care and caution

exercised for agricultural pesticides.

(iii) Biological control:

Biological control has been used for the control of many insect pests either
individually or as a part of integrated pest control programme. Control of uzi
fly through biological means (hyperparasitoids), however, has a special
relevance since the host itself is an insect and insecticidal measures cannot
be taken against a pest associated with an insect host. A number of
parasitoids parasiting on uzi fly pest of silkworm have been identified as
follows:

Studies carried out on them indicated that

(1) They can be cultured and multiplied with minimum efforts,
(2) They can search host even up to a distance of about 30 meters,
(3) Females oviposit the eggs inside the wall of the host puparium, which on
hatching feed on the host tissue to develop into adults,

(4) Newly emerged adults cut a hole on the wall of the host puparium, come
out and repeat the life cycle,

(5) Unfertilized females of the parasitoid reproduce parthenogenetically, and

(6) Developmental period varies from species to species and season to

season, the average range being 13-33 days.
 A systematic programme integrated with other measures is required to be
taken up for the biological control of uzi fly.

2. MINOR PESTS
Mulberry silkworm is also attacked by several species of other insects like Coleopterans,
Alphitobiuslaevigatus, LypropscuticollisFacion, Necrobiernfipes (Degeer),
Triboliumcastaeneum and many species of genera Dermestes; a dermapteran Labia
arachidis (Yersin); tachinids, Crossocosmiazebina Walker and Ctenophorocerapavida
Mei gen and an acarid Pediculoidsventricosus (Newport). These pests are generally of
minor economic importance in restricted localities. The important ones which cause
occasional damage are described below.

2.1. Dermestid beetles

This group of insects belong to the family Dermestidae of the order coleoptera. They
often attack pupae and adult silkworms in the grainages, and
mostlycauseextensivedamage to the stored cocoons.
Thoughalargenumberofspeciesofdermestid beetle have been reported, description of
the more important ones viz., Dennestesater, D. cadverinus, D. vulpinus,
Anthrenusverbasci and A. pipinellae Fab. are given below:

They may exist in other countries as well.

(a) Life Cycle

(i) Dennestesater: Black, It measures about 7 mm in body length. Females start

ovipositing in about 5 days after exclusion. The egg is milky white, elongate with an
average measurement of 1. 90 mm in length and 0.48 mm in width. Incubation period
varies from 3-6 days. Newly hatched grub is white which gradually turns to brown in first
instar itself. The colour of the grub turns to black from second ins tar onward. The first
instar grub is about 2.4 mm in length. Morphologically the different instars are similar
except in size. Grubs, in general, are spindle shaped and are covered with hairs of
various length. The grub undergoes 4-6 moults in about 27-28 days. On an average,
pupal period occupies about 7-8 days. Freshly emerged adult changes its colour from
light yellow to dark brown.

(ii) D. cadverinus: Adults of D. cadverinus are ovalelongate and dark brown in colour. It
measures about 1 cm in body length. The female beetle deposits its eggs in the crevices.
The elongateoval egg is about 2 mm in length and milky-white in colour. Eggs hatch in
about 7 days. The spindle shaped grubs,are reddish brown in colour. They moult 5-7
times in about 1-2 months and attains a length of about 1.5 cm. Body of the grubs are
covered with hairs. Although the insect generally passes the winter in the adult stage,
since the time of metamorphosis varies, both the grub and pupal stages may be
encountered.
(iii)D. vulpinus: Adults are shiny reddish brown to black in colour, subparallel in shape
and clothed with hair. The males are slightly smaller than females, bear a pit and a brush
of hair on the fourth sternite. The four short basal tarsal segments of foreand midlegs
lack the fine golden testaceous hair and also do not form distinct ventral pads. The adult
female lays eggs in batches of two or three, some- times single. The number of eggs laid
ranges between 198 to 845. Thecreamywhiteeggiscylindrical andoneendslightlybroader.
Theincubationperiod ranges from 2-4days. The fullgrown larvae are dark brown with a
medium yellow stripes dorsally and is densely covered with hairs. They avoid light and
moult 7-14 times. The larval period ranges from 25- 60 days mainly depending upon the
climatic conditions. It pupates in the last larval skin and the adult emerges in about 5-8
days. The number of generations in a year varies from 3-6.

(iii)Anthrenw, verbasci: Adults of A. verbasci are convex, slightly elongated and round
with yellow-white scales on the black colourof body. The female beetle lays about 20-
100 oval shaped milky-white coloured eggs each measuring about 0.5 mm in length.
Eggs are generally laid in wooden slits and crevices. Grubs hatch in about a month's time
and moult6-7times and attain thesizeof3-4mminlength. Theyaregrayish-brown in colour,
swollen at the tail with an elongated tumbler shaped body. These
beetlesoverwinteringrub stage and become pupaeduringsummermonths. In about a
month's time the adults emerge from these pupae.

(v) A. pipinellae: A. Pipinellaeresembles A. verbasci but produces two generations in a

year.

(b) Type of damage and symptoms

Grubs and adults of most of the species of Dermestid beetles are attracted by the smell
of stifled and stored cocoons and the dried pupae inside. They bore into the cocoons
and eat the dried pupae. They also damage pierced and melted cocoons which are
stored within the grainage building for the longer duration. Sometimes they also attack
adult silk moths, eggs and rarely the young silkworm larvae. Presence of cocoon pierced
at several 75. Silkworm cocoons damaged by dermestid beelle places in the cocoon
storage rooms and also the presence of the egg laying silkworm adults in the grainages
damaged mostly on the abdominal parts are indication of attacks bydermestid beetles.

(c) Period of occurrence

Throughout the year.

(d) Prevention and control

1. Storage of rejected cocoons and perished eggs for long period should be avoided. 2.
The rearing house and cocoon storage rooms should be cleaned periodically.
3. Before and afteremergenceofsilkmoth the grainage premises should be cleaned.
4. Wooden article of the storage room and grainage should be dipped in 0.2 per cent
malathion solution for 2-3 minutes. After 10 days the trays should be thoroughly
washed in water and sun dried for 2-3 days before reusing.
5. Passing of hot air (50-60°C) into the storage rooms and maintaining low
humiditylike30percentand below help to kill the beetles.
6. Fumigation of dried cocoon storage room with methyl bromide at 0.5 g per 3 m2 for
three days kills all the stages of beetle. Necessary precautions must be followed for
using this chemical as fumigants. This treatment should be undertaken, if the cocoon
storage rooms are away from the grainage or rearing house.

a. Silkworm tachinia fly

(a) Life Cycle:

The adult fly is grayish black with pale ventral aspect. The male is longer (15 mm) than
the female (12 mm). Both male and female flies have reddish-brown, semi-circular
patterns or dots dorsally on either side of their abdomen. The red dots are more
prominent in male fly. The pro- and mesa-thorax have five longitudinal lines. In other
aspects, the morphology is similar to E.sorbillans. A single female fly lays 3,000-5,000
oval shaped eggs which are black in colour and each measures about 0.2 mm in length.
Unlike the uzi fly, which lays eggs directly on the body of the silkworm, this fly deposits
eggs on the ventral side of the mulberry leaf along the vein. The eggs laid on the
mulberry leaves remain viable for about a month. If the eggs are not ingested by the
silkworm within about one month they perish. The egg ingested by the silkworm
together with mulberry leaf hatch out in the gut through the action of the silkworm
digestive juices.
The young maggots bore their way through the wall of the digestive canal and penetrate
into the 4th-7lh ganglia of the nervous system and remain there for one to two weeks,
later move and attach themselves to the spiracles of the host larva by their posterior
end. These maggots breathe through the host spiracles and feed upon the haemolymph
and the body lissues of the host. The tissues of the silkworm around the spiracle dies
and become black. The mature maggots which are paleyellow, oblong and about2 cm
long come out of the silkworm/cocoon through the pupa mainly during morning hours
and pupate into soil to a depth of 10 cm in about a day. The puparia hibernate in soil
during cold season. The adults appear during midApril and the emergence of the
tachinia fly coincides with sprouting of mulberry in Japan. This has one generation in a
year.
(b) Type of damage and symptoms:
The silkworms which are parasitised in the 3rd and 4th instar die invariably either before
or during mounting of the hosts but in case of infestation in 5th ins tar, the silkworms
generally spin cocoon and transform into pupae. The hosts succumb later at the time of
emergence of the mature maggots. In the early stages of infestation, the infested host
larvae cannot be distinguished from healthy silk worm. As the time advances, the
silkworm becomes inactive and loses appetite. In the advance stages of infestation dark
irregular spots are observed around the spiracles of the host larva.
(c) Periodofoccurrence:
May to September
(d) Management:

(i) Planting of mulberry away from pine plantation as it is reported that more eggs are
laid on mulberry, if near pine plantation.
(ii) Dipping of the harvested mulberry leaves in hot water at 50°C for 5 minutes to kill
the eggs.
(iii)Fumigation of the harvested mulberry leaves with naphtalene 5 g/1 000 cm3 before
feeding silkworm to kill the eggs.
(iv)Spraying of VCMP (2-Chloro-1-2,4,5- trichlorophenylvinyldimethyl) on the ground to
prevent the escape of this fly from cocoon storage room.
(v)Spraying of 0.05 per cent DDVP in the mulberry garden. Safe period - 11 days.
(vi) Sprinkling of a mixture of the natural enemy, a fungus, Isariafumoso-rosea Wize and
saw dust on places where maggots are likely to gather.
(vii)All the measures suggested to prevent infestation and pupation of the maggots of E.
sorbillans in and around rearing house should also be followed.

b. Himeuzi fly, CtenophorocerapavidaMeigen (Tachinidae)

(a) Life Cycle:

Adults are dark blue with metallic Juster, measuring 7-9 mm in body length. An adult
female lays about 1,000-2,000 eggs which are black in colour, oval in shape and each
measures about 0.15 mm in length. Eggs are laid on the ventral side of the leaves. Eggs
which are swallowed by the silkworm larva enter the alimentary canal and hatch. The
maggots lodge temporarily in the silk gland and finally settle down with its caudal end
fixed to the dorso-thorax region of the host larva. Mature maggot measures about 10
mm in length. In about 10 days these maggots escape from the host killing the host larva
and pupate in the soil. In 1-2 weeks adult flies emerge. It has 4-5 generations in a year.
The first adult appears in the first halfof May.

(b) Typeofdamageandsymptoms: Damage caused is similar to C.zebina. On the skin of

the affected part black scars about l-2mm in diameter are observed.

(c) Period of occurrence: From May to Onset of the Winter season.

(d) Management: As in C. zebina.
 c. Mite
(a) Life Cycle:
The adult female is spindle shaped while them ale is oval shaped. Head is triangular. The
thorax-abdomen carry four pairs of legs each having small claws. This mite is an
ovoviviparous. In the body of the female, the young acarids hatch out from the eggs and
pass out in the form of adult like small acarid. Each adult female produces about 100-
150 youngones. The newly born mite is about 0.2 mm in body length and light yellow in
colour. The males are produced first and the females later. Each male after mating with
some females dies in about a day. A mature female in which the eggs are fully
developed, the posterior half of the body becomes extra-ordinarily large to assume a
spherical shape (about 1 mm in dia). The fertilized female on getting a suitable host
attaches itself with claws and suckers present on the legs. This mite passes through 17
generations in a year. Each generation time ranges between 7-18 days.
(b) Type of damage and symptoms:
The larva, pupa and adult silkworm are attacked by this acarid. Mainly, the young age
larval and pupal stages are attacked. The females lodge themselves on the soft skin
between the segments of host larvae and pupae and obtain nutrition. Furthermore,
their saliva contains a kind of toxin which ultimately kills the host. After being infested,
the silkworms almost stop feeding and become sluggish, the body turn purple brown
and yellowish brown fluid is vomited. Defecation is difficult and beaded faeces are
attached to the anus. The skin surface of the attacked host bears several rough and
uneven black spots. Silkworms attacked during moult fail to pass the moult. The worms
die in a day or two. Infested pupae develop lesions, the body is blacken and they fail to
moult into adult. The suspected worm should be placed in a black box and gently
knocked a few times. By doing so, this acarid can be seen in the box through a
magnifying glass.
(b) Period of occurrence:
Mostly from May to middle of September.

(d) Management:
(i) On discovery of the attack by this acarid, the rearing rooms and trays should be
replaced.
(ii)The rearing appliances should be disinfected with steam.
(iii)Cotton, wheatstraworricestrawshould not be kept to dry near the rearing rooms or
rearing appliances.
 (iv)Pre-rearing disinfection should be carried out with sulphur at the rate of 30 g sulphur
to a cubic foot or spraying of the rearing room and appliances with a 1 :500 solution of
an acaricide.

Potential, strengths and challenges of sericulture

industry in India
R&D achievements like development of indigenous mulberry varieties with highest leaf
yields in the world, new bivoltine silkworm hybrids eminently suited to the tropical regions
of the country, farmer-friendly technologies, cost-effective new package of practices for
cultivation of food plants, rearing and reeling coupled with huge natural and man-made
resources and trained manpower clearly indicates the future prospects of sericulture
industry to emerge as a promising indicator of economic development for the upliftment of
the socially deprived communities and the downtrodden.
Seri-bio-diversity:
Among 34 mega biodiversity countries in the world, India is home to many species of insects
with a diverse silk moth fauna. In addition to the diverse silkworm races, there are vast
genetic resources of mulberry, tasar, muga and eri host plants spread over diverse
geographical locations. This offers a great opportunity for economic utilization of the
natural flora and fauna. However, due to deforestation and destruction of habitats, there is
a challenge to bring about development without disturbing the ecological balance.
Sericulture and national economy:
In India, sericulture related activities ensure the livelihood security of over six million
families spread over in some 59,000 villages across the country. The silk sector is also a
valuable foreign exchange earner for the country. The export earnings stood at Rs. 2,353
crores during 2011-12. In addition, there is an opportunity to double the export earnings
with the free trade atmosphere in Europe and USA. It is estimated that India needs 25,000
MT of raw silk per year to meet its domestic requirement. The growing demand of silk in the
domestic market can make the industry a valuable enterprise which in turn can provide
employment for the rural masses ensuring assured economic returns at the individual
family level.
Sericulture has been a labour-intensive agro-based industry with several activities like, food
plant cultivation, silkworm rearing, silk reeling, twisting, degumming weaving, dyeing,
printing and finishing and garment manufacturing. The industry is spread over several
states. It has a long tradition in states such as Karnataka, Andhra Pradesh, Tamil Nadu, West
Bengal and Jammu and Kashmir. It is at various stages of development in the non-traditional
states such as Uttaranchal, Uttar Pradesh, Madhya Pradesh, Chattisgarh, Orissa, Bihar,
north-eastern states, etc.

The number of crops range from one to six in a year in different sectors and in different
areas. Mulberry provides one crop in J&K and Uttaranchal, two in most other hill and
temperate areas and 3 to 5 in rain-fed and irrigated areas in other states; and eri has a
similar situation with 3-4 crops but only in rain-fed areas; tasar with 2-3 crops and muga
with 5-6 (2-3 commercial) crops. Thus silk industry at production stage provided almost
round the year employment in many areas. The processing part almost provides equal
employment. With the present level of productivity every hectare of irrigated garden is
estimated to provide full time employment to around 16 persons (5 – up to cocoon
production, 9 – for reeling and 2 – for weaving) up to weaving and many more down the
line. The activity from weaving, finishing, garment manufacturing, etc. has scope for huge
value addition and exporting. In spite of a slump or stagnation in Indian silk production, the
exports have been increasing year after year.

Sericulture and women empowerment:

Women contribute to a little less than 50 % of the country’s population and most of them
are largely rural based, deriving their livelihood through agriculture and other land based
activities, either as family members or wage earners. As a cottage industry, sericulture
provides ample wok for women in the rural areas particularly in silkworm rearing and
reeling, while men, largely work in the field and in weaving.
The involvement of women in different activities of sericulture is about 53 % and their
contribution in the onfarm activities understandably is lower than that in post-cocoon
activities. Sericulture is an ideal avocation for women because of the following factsBeing
rural based, sericulture needs less specialized skill and hence, suits women well. Involves
 mostly indoor activities, less physical energy and manual labour. Work is evenly spread over
during the day, with intermittent gaps, offering leisure time and proximity to living place.
Minimum investment with long life and short gestation period. Continuous job with
frequent income and scope for utilizing several by-products for value addition.

Sericulture and rural development:

Sericulture being a farm-based enterprise is highly suited for both large and small land
holdings, with low capital investment. The very nature of this industry with its rural based
on-farm and off-farm activities and enormous employment generation potential has
attracted the attention of many planners and policy makers to recognize the industry as one
of the most appropriate avenues for socio-economic development of a largely agrarian
economy like ours.
Generally, silk goods are purchased by the urban rich and middle-class consumers and it is
estimated that around 57 % of the final value of silk fabrics flows back to the primary
producers in rural areas. Sericulture can also play a very vital role in alleviating rural poverty
due to its high work participation rate and thereby can check migration from rural to urban
areas.
Sericulture and employment generation:

Raw silk production is the most appropriate tool to provide gainful employment to these
poorer sections of the society, as net incomes range from Rs. 12,000 to 70, 000 per annum
depending upon the variety of the silk to be produced and the unit area (under host plants).
It is estimated that sericulture can generate employment @ 11 man-days per kg of mulberry
raw silk production (in on-farm and off-farm activities) throughout the year.

Steps to improve productivity and quality:

During the past decade a few highly productive breeds have come to use in India. The
mulberry variety, V1 for the irrigated gardens has been reported to yield about 65 MT of
leaf per hectare per year (i.e., the world’s highest) with the recommended inputs at the
most ideal situation and the CSR series of bivoltine silkworm breeds, which can yield
international grades of silk (2A to 4A) and high productivity with a renditta of 6 (around 6 kg
cocoons yielding 1kg of raw silk). It is claimed that about 65 kg of bivoltine cocoons are
produced from 100 disease free layings (dfls) of CSR breeds on an average, while the multi-
bivoltine hybrids, which constitutes over 90 percent of the silk production in the southern
region, yields around 55 kg per 100 dfls. The fodder consumption also varies 8-15 kg per dfl
by different breeds and correspondingly the cocoon production. It is possible to produce 2A
or 3A grade silk from the CSR breeds using the improved reeling machinery coupled with
improved package of practices.
However, in the light of X Plan experience, it is to be seen that this increased productivity
has been in limited areas and with those farmers who were either exposed to Government
schemes or could adopt it otherwise. Consequently, this increased productivity has failed to
make any significant difference in overall production.
 Cross breed production constitutes about 95 percent of the silk produced in India
dominating the bivoltine silk production. Cross breed silk is very conveniently used on
handlooms while bivoltine silk forms an essential requirement of power-looms at least for
the warp and this is now being imported from China.
Main steps are describe below
1. Evolution of appropriate cost-effective technologies through focused research projects
addressing constraints and maximizing the production of quality eggs.
2. Teaming up of sericulture scientists with molecular biologists, bio-engineers,
immunologists, textile technologists, clinicians, experts from industry and a host of other
stakeholders in charting out a new road map.
3. Adoption of region and season specific approaches in the development of superior
breeds / hybrids and feed package of practices.
4. Establishment of close linkage between forward and backward sub-systems for greater
efficiency and synergy as sericulture and silk industry is highly scattered and unorganized.
5. Identification and promotion of potential clusters for Bivoltine and Vanya silk production
in potential traditional and non-traditional areas.
6. Skill up-gradation through structured and specially designed training programs.
7. Establishment of linkages among the four identified production sub-systems viz., seed,
cocoon, yarn and fabric.
8. Capacity building for production and supply of adequate quality planting material,
silkworm seed, reeling cocoons and silk yarn through promotion of largescale production
units with required techno-financial support.
9. Development and promotion of participatory extension system for effective adoption of
technologies by similar stakeholders.
10. Protection to some extent of Indian silk market from Chinese cheap raw silk and fabrics
by implementation of anti-dumping duty.

11. Effective utilization of by-products for value addition.

Growth rate and demand for silk:

The growth rate of silk production in the country has been at around 8 percent per annum
while the demand for silk has been approximately growing at 10 percent per annum. The
demand for silk has been ordinarily arrived at by adding the imports to the domestic
production and this is estimated to cross 33,500 MT.
The indigenous silk primarily caters to a strong and growing domestic market estimated to
have an annual growth rate of 10percent. The weaving sector is estimated to consume over
26,000 MT annually. There has been an increase in the number of power-looms, which need
 good quality yarn and the shortfall is made good through import of yarn, especially from
China.

Research and development:

Sericulture in India is a sustainable farm-based economic enterprise positively favouring the
rural poor in the unorganised sector because of its relatively low requirement of fixed
capital, and higher returns on investment. Several socioeconomic studies have affirmed that
the benefit-cost ratio of sericulture is the highest among comparable agricultural cash crops
in the country. It generates a steady stream of income (on average, a net income of up to Rs
45,000 annually in about 4 to 5 splits, from one acre of irrigated mulberry) for its
practitioner. Currently, about 6 million persons are employed in the silk sector. Export of
Indian silk products during 2005-06 was valued at US $ 713.39 million, according to data
supplied by DGCI&S.

Amendment to central silk board act:

The Parliament of India recently passed an amendment in the Central Silk Board Act making
a provision to bring a regulatory mechanism for production and sale of silkworm seed in the
country. This ensures i) production and sale of seed of authorized races only; ii) control on
unauthorized production and trade; iii) Control and prevention of entry of untried and
untested hybrids from other countries likely to be carrying diseases and other unknown
risks. This enhances quality of seed and protects the interests of farmers by safeguarding
against sudden crop losses and low productivity due to unidentified and un-guaranteed
seed. Efforts would be made to expedite the formation and implementation of suitable
Rules for the speedy development of Sericulture Sector.

Though Indian breeds are having potential to produce the same quality of Bivoltine silk as
that of China, there has been lack of sufficient thrust on the adoption of improved
technologies, strict disease control measures, lack of quality leaf due to insufficient inputs
to mulberry garden, use of young age silkworms, appropriate montages and lack of grading
system for cocoons and quality based pricing system. The success of Chinese sericulture is
due to extensive pushing of technologies through an organized effort and extensive use of
organic inputs which maintain the soil health and therefore a healthy crop. The experience
of Japan International Cooperation Agency (JICA) Project and the Institute Village Linkage
Programmes in Southern India has shown similar results with Bivoltine. It is therefore,
suggested to replicate the models through a cluster approach in all other places.

It involves –
• Large-scale Bivoltine seed production
• Supply of chawki worms to all Bivoltine farmers
• Supporting the farmers with required infrastructure like rearing house and improved
rearing appliances under the existing CDP schemes
• Extensive training and demonstrations by bringing the active participation of Self Help
Groups and Expert Farmers
• The efforts shall be on a cluster basis which include a grainage linked to Chawki Rearing
Centres (CRCs), Expert Farmers and Commercial Farmers and the Reelers.

Analysis of Indian Silk Industry

Mulberry Sector Strengths:

• One of the most profitable activities in rural sector

• Comparative advantages such as large production base, availability of skills, land and
labour, easily adoptable technologies
• Fairly established infrastructure, silkworm breeds, proven farmer – friendly technologies
• Short gestation period
• Favourable agro-climatic conditions and sustainable technologies
• Strong domestic demand coupled with use of silk garments on festive occasions

• Tradition of creating exclusive designs and items having niche market

• Popularity of hand woven silks in the west which have no threats of quota like other fibres
• India holds a monopoly in the production of yarn dyed silk fabrics
• Availability of indigenous technology at low cost
Weakness

• Handling live biological material always involves risk

• Inconsistency in output quantity and quality due to natural vagaries
• Poor technology transfer and extension support
• Inadequate market linkages in states other than Karnataka
• Highly decentralised with small and scattered production

• Poor credit from financial institutions

• Obsolete equipment with low productivity and quality
• Thin fluctuating margins resulting in lack of focus on modernization leading to poor quality
of the produce
• Dwindling family skills due to shifting for remunerative employment
• Lack of quality consciousness
• Extreme fluctuations in cocoon and raw silk prices
Opportunities
• High rural employment potential
• Discontinuation of silk production by developed countries due to high cost of labour

• Development of marketing avenues for silk products

• Increasing domestic consumption of silk which is expected to reach 35,000 MT in next few
years • Shifting of garment manufacturing from Western Europe to Asian countries due to
high labour cost and the garment export from India has been increasing steadily
Threats
• Falling prices due to dumping of Chinese silk and fabrics
• Inability to meet the changing quality requirements
• Small reelers and weavers are dependent on mahajans for whom they work on piece rate
basis often subject to exploitation
• Heavy dependence on single source of imported silk for exports is risky.

• The indigenous silk is more expensive than the Chinese silk and imposition of antidumping
duty is a temporary relief and subject to revision and a serious potential threat

• Lowered water table and prolonged drought

Non-Mulberry (Vanya) Sector
Strengths
• Rearing on nature-grown host plants keeps off the cultivation cost
• Abundance of manpower in the tribal areas

• Availability of natural population which forms a sizable collection of tasar cocoons

• Augments the earnings of the tribes in the forest areas
• Strong market demand for vanya silk products,
• Natural colours are preferred and hence there is less pollution from the use of dyes
• Niche market for the traditional products

Weaknesses
• Wild varieties are prone to natural vagaries,
• Deforestation leading to reduced availability of food plants
• Non-amenability of some high productive eco-races to human handling
• Inadequate silkworm seed supply

• Limited opportunities for breeding better breeds

• Out-dated reeling appliances with low productivity and hazardous reeling practices
• Lack of interest on the part of the State Governments
• Meager state budget for sericulture

• Lack of initiatives in new designs and product diversification,

• Exploitation of the primary producers by middlemen or traders
• Lack of efficient technology transfer system
Opportunities
• Low production compared to its demand

• Generates rural employment

• No competition from heavy industries
• Attractive market potential
• Huge manpower availability in the silk growing areas
• High skills in weaving and designing

• Special attraction for the natural golden luster of muga silk

Threats
• High production cost
• Outdoor rearing results in uncertainty in crop output
• Deforestation and reduction in food plant resources

• Reeling and weaving are done on primitive appliances leading to poor quality and
productivity besides being hazardous to health

• Lack of awareness about the consumer demands due to their confinement within the area

Textile policy of government of India

Focus will be on achieving international standard in all varieties of silk. Steps will include:
• Improving Research & Development and the effective transfer of technology at all stages;
• Considerably improving the production of non-mulberry varieties of silk;

• Augmenting efforts for the spread of bivoltine sericulture;

• Encouraging clustering of activities of reeling and weaving and strengthen linkages
between the producers and industry;
• Periodically reviewing the import policy for raw-silk taking into account the balanced
interests of the sericulturists as well as export manufacturers.
• Large scale expansion of the production base through expansion of area under silkworm
food plants to the potential non-traditional areas
• Tapping and promoting raising silkworm food plants in unused or waste or degraded lands
belonging to Panchayats, forest and other entities
• Developing the unused silk farms and other seed production and reeling infrastructure
available with the State Governments and putting them to use
• Following selective approach for various types of silk cultures and practices based on
regional differences
• Involvement of large private entrepreneurs to the seed production cultivation and reeling
and allied activities promoting contract farming
• Promoting Public-Private Partnership in innovations, development and transfer of
technology
• Inter-linking of various activities in sericulture and allied activities through a cluster
approach
• Involvement of SHGs, Panchayats and also voluntary organizations in the sector and other
local bodies and bankers in the development process

• Development of poorer sections by providing assistance to upgrading lower versions of

machinery consuming lower quality cocoon and yarn adding value to the product

• Development of small entrepreneurs for production and supply of biological inputs, or

services required in the silk industry

• Product diversification and innovation of new products of curiosity and attraction

• Generic promotion of silk and brand promotion
• Promoting traditional crafts and ethnic designs of indigenous origin in the major markets
inside and outside India
• To enlarge employment opportunities, income and sustainable livelihood in rural areas
through expansion of area under silk production
• To increase the production, productivity and quality of silk through transfer of technology
and modernising various sections of the industry
• Exploit the full potential of sericulture developing the linkages through cluster approach
• To bring in large scale private participation and private investment in promoting the silk
industry

• To optimise the output of human power through knowledge and capacity building
• To improve the productivity of silk per unit area of land
 • To enhance the quality of silk produced at economically viable costs to substitute import
of raw silk
• To innovate high end exportable products to boost exports and thereby the national
economy
• To enlarge the annual raw silk production base to 26,000 MT
• To enlarge the area under mulberry silkworm food plants to 2.50 lakh ha by adding 0.50
lakh ha
• To provide remunerative employment to about 77.04 lakh persons

• To optimize the output of the human power engaged in silk production

• To raise the average national mulberry silk productivity to 100 kg/ha per year from the
existing 85kg
• To bring down the cost of production of mulberry raw silk closer to that of imported silk
yarn
• To increase the production of non-mulberry silk yarns to an average of 150 gm from the
existing 125 gm per person-day
• To enhance export earning to Rs. 4,500 crore per anuum.

It is estimated that one hectare of oak plantation can yield about 6 kg of silk in the sole crop
while the tropical tasar food plants can yield around 12 kg in two crops. Muga with two
commercial crops can also yield around 16 kg of raw silk per hectare. Ericulture in the North
Eastern states gives about 25 kg of spun silk per hectare. They largely depend on nature grown
food plants with total leaf harvest.
Ericulture in the non-traditional states based on castor or tapioca which is primarily grown
for oil seed or tubers, 250-350 dfls can be reared per hectare per year, by harvesting 25-30
percent of the leaves, which can yield about 6-8 kg of spun yarn / ha. If spun on mill it will
be 5-7 kg only. The following benchmarks have therefore been set for non-mulberry;

Tasar Sector
Seed:
The envisaged tasar silk production requires about 1.13 crore. It is necessary to plan for
bridging the gap of 0.34 crore of commercial dfls. This requires upgrading 8 Basic Seed
Multiplication and Training Centres (BSM&TCs) as Nucleus Seed Stations. These BSM&TCs
will be assisted with necessary input support, which includes strengthening of existing
buildings, construction of grainage houses and providing equipment along with plantation
support. Alternatively, some of them can be sanctioned to the NGOs or SHGS having
expertise in this field. They can be further trained at the CSB Institutions and the units
maintained under close supervision of the experts.
 In tasar sector, the basic seed supplied by CSB is not multiplied to the desired level of
multiplication at the state level. Present level of multiplication is less than 1:3 against the
target of 1:10 and it is necessary to achieve the minimum multiplication ratio of 1:8 in tasar
to bridge the wide gap between demand and supply.
It is envisaged to support 1000 Private Graineurs and 10 Pilot Production Centres (PPCs)
under tropical tasar sector. In oak tasar sector, 15 grainages, 1500 seed and commercial
rearers will be supported to produce the required quantity of quality commercial dfls.
Plantation and Cocoon Production:
Though tasar rearing is largely done on forest trees, systematic plantation closer to the
villages can provide good support for tasar culture besides providing a green cover. It is
therefore targeted to raise 10,000 ha under tasar food plantation. It is proposed to take the
help of the Local Gram Panchayats, Forest Protection Committees (Vana Samrakshana
Samithis), SHGs at village level, Forest Department, NGOs, etc. for the purpose. Wherever
possible, the schemes for development of tasar food plants will be dovetailed with the
afforestation schemes of the Department of Forest and Environment. Chawki rearing with
good care in compact area has been a good approach to check loss at younger stages and
improve the overall performance. It is therefore proposed to support 15,000 farmers for
raising and maintenance of chawki garden. On similar grounds, it is proposed to raise 1500
ha of oak tasar food plantation.

Eri Sector
Seed Support:
The requirement of seed has been estimated to be 3.37 crore. The present production is
2.39 crore and facilities need to be developed for the additional of 0.98 crore dfls. To
produce the additional dfls, 5 SSPCs will be strengthened. These SSPCs will be assisted with
necessary input support, which includes strengthening of existing building, construction of
grainage houses and providing equipments along with plantation support. To increase the
quality eri silkworm seed in the country, the Eri Silkworm Seed Organisation (ESSO) will be
strengthened. To produce the additional dfls, the 5 Eri SSPCs will be assisted with necessary
input support, which includes strengthening of existing building, construction of grainage
houses and providing equipments along with plantation support. It is also envisaged to
support 2000 Eri Seed Rearers / Pvt.Graineurs, 50 Eri Farm cum grainages to produce the
additional quality dfls in the country.
Plantation and Cocoon Production:
When cultivated, only perennial food plants proved economical. They include kesseru,
payyam and barkesseru (specified species only). However, no specific target has been kept.
Outside north eastern region, Castor and tapioca are grown as agriculture crop for oil seed
and tubers. Hence there is no need to provide support for cultivation of these species on a
regular basis. It is proposed to enhance their income by partial utilisation of leaves (up to 30
) for ericulture without affecting the yield of the primary crop. It needs support for rearing
appliances and rearing shed. It is envisaged to cover 4800 ha (12,000 acres).
 Muga Sector
Seed:
The seed requirement to reach the production target is estimated to be 1.30 crore. The
present production is around 1.05 crore and an additional 0.25 crore commercial dfls have
to be per annum. This needs strengthening of the existing P4, P3, and SSPC units of MSSO.
The proposed support includes strengthening of existing building, construction of grainage
houses and providing equipments along with plantation support. In addition, it is necessary
to support 700 Muga Private Graineurs, 20 Muga Farm cum grainages to produce the
additional quality dfls in the country.
Plantation and Cocoon Production:
It is envisaged to raise 4000 ha (10,000 acres) of muga food plantation during the period.
For this, 500 farmers will be assisted for raising nursery for muga food plants. Approach for
Achieving the Goals: 12.92 Region-Specific Approach: The agro-climatic, demographic and
other factors vary greatly from region to region. Different areas are suited for different
types of silkworms and different breeds or different practices. The practices also vary with
the terrain.

Mapping and Selection of Suitable Areas:

The selection of the enterprise, the practices etc. are on a region specific approach. It shall
be on the basis of i) suitable soil; ii) temperature (between 200C and 350C at least for six
months in a year); iii) irrigation facilities or good rainfall spread over 7-8 months; iv) wage
pattern; v) dependency on agriculture and agro-enterprises; vi) competing crops; vi)
amenability of the target groups to learn, systematise and potential entrepreneurial
qualities; viii) facilities for quick transport of the green cocoon to potential reeling clusters;
potential market areas, etc. By following the approach, it is possible to plan the allocation of
the funds prudently. While the efforts shall be to tap all possible non-traditional areas, we
will be cautious in entering new areas. The food plant species or varieties, silkworm breeds
or races, the cultivation practices, etc., have all been well defined for different regions,
which will be followed.
Project Mode Approach:
All the development activities shall be on a project mode with clear goals, measurable
targets, resources, and time schedule based on established facts and defining the project
area. The activities and their measurable outputs shall be monitored and reviewed on a pre-
drawn Project Design Matrix providing required guidance and direction to implementing
persons. CSB shall provide its expertise to the Department of Sericulture and all
implementing partners to this extent. A pool of CDP schemes shall be chosen along with
suitable modification to be dovetailed into the project. The Centrally Aided projects can be
dovetailed to the state projects or the projects of other Ministries such as Ministry of Rural
Development, Ministry of Agriculture and Cooperation, Ministry of Forests and
Environment, and also the other sectors in the Textiles, like Handlooms, Powerlooms, etc.
which provide critical forward linkages to Sericulture Sector.
Cluster Approach:
This works well in the under developed and new areas and require extensive efforts in
organising various inter-linked groups in the supply and beneficiary chain. It is essential to
involve and plan from the village panchayat level, taking help from the reputed Voluntary
Service Organisations, Rural Development Agencies, Financing Institutions, etc. from the
project formulation stage to facilitate organising producer groups and integrating them into
the production chain to reach a marketable end product within the geographical niche. This
essentially involves grouping and organising a large number of (around 200-250) primary
(cocoon) producers, reelers& twisters, weavers and all others involved in processing,
trading, etc. including allied activities. CSB would implement the schemes of Pre- and Post
Cocoon sectors in the form of clusters and not in any scattered manner. Each cluster would
have its own reeling and marketing forward linkages. Old clusters too would be provided
with these forward linkages.
Public-Private Partnership Enterprises in Sericulture:
The interests of different partners in this system when joined together can have a
synergistic effect. This can be very useful in developing working economic or commercial
models through which the technology can refine and penetrate easily. This can be useful in
R&D institutions as well. Developmental programmes can be dovetailed to the CDP
Schemes while R&D programmes can be taken with collaboration between the Institute and
the Entrepreneur. CSB would attempt to ensure at least matching private resources in the
sector as its own Plan size.

Cooperative Farming:
It is proposed to organize the activities particularly in the new areas under cooperative
system on line with cotton, sugarcane and dairy. The purpose is to bring all essential
linkages into the system to organize sericulture as an economic activity. The help of reputed
NGOs, the local authorities, Financial Institutions etc. are essential to organize this activity.
Funds can be taped from Ministry of Rural Development and other similar Departments,
which can be dovetailed to CDP Schemes.
 Contract Farming:
To keep up the production and quality at international standards, it is necessary to make
large investments in seed production, farming, reeling and processing. It is also possible to
link up large number of small farmers to few large entrepreneurs capable of making huge
investments and organizing as in castor cultivation, sugarcane cultivation, etc. This requires
heavy dose of technical inputs for capacity building. The help of NGOs and other rural
development organizations, Banks etc. can be taken and the CDP components dovetailed to
this. Providing the required inputs, maintaining the quality, monitoring and marketing is
much easier in this system. Large bivoltine grainages, chawki rearing centres automatic or
multi-end reeling units can be an integral part of this system.
Inviting Large Entrepreneurs:

It is proposed to bring in large investors in Silkworm seed production and reeling activities
with latest facilities including all linkages. The existing CDP Schemes can be availed for these
activities. It is also proposed to keep the scheme for Establishment of Large Bivoltine
Grainages or upgrading the infrastructure for bivoltine seed production open for State
Departments and suggests CSB to upgrade some of their seed production centres for
bivoltine seed production.

TECHNICAL TERMS ASSOCIATED WITH SILK CULTIVATION

1. Voltism- It refers to number of life cycles per year. Depending upon ecorace a typical
silkworm may have one (Uni), two(Bi), three (Tri) or Multi(more than three) life cycles.
2. DFL- Disease free laying. A DFL is a defined as Disease Free Laying that is a group of eggs
laid out by a moth which has been certified as disease free. Normally it consists of 200
healthy eggs. After emergence from the cocoon male moths immediately couple with
female moths. After a period of 24-36 hours female moth lays eggs in about three
batches. These eggs are cleaned washed and examined under the microscope for
diseases specially pebrine. After a batch ic certified as disease free then only it is used
for rearing in the field.
3. Chawkie rearing- Initially laid eggs when transferred in the field are hatched under
supervision in few selected shrubs for a week. This natal stage rearing is called Chawkie
rearing. After a week the one week old larvae are spread all over the forest areas.
4. Pebrine-Pébrine is a disease of silkworms, which is caused by microsporidian parasites,
mainly Nosema bombycis and to a lesser extentVariomorpha, Pleistophora and
Thelophaniaspecies. The silkworm larvae infected by pébrine are usually covered in
brown dots and are unable to spin silkworm thread. Louis Pasteur was the first one to
recognize the cause of this disease when a plague of the disease spread across France. It
is the most dangerous silkworm disease and often leads to epidemic form there by
destroying crops not only at local level but at state and even national level. Precaution
includes disinfection and burning of the ground soil surface.
5. Diapause- After the cocoon has been spun and the pupa sets inside the cocoon it goes
into hibernation or diapauses. In case of Tasar during the first crop at the onset of
monsoon the pupa goes into diapause for one week. Since there is still sufficient
humidity it emerges as a moth and the lifecycle is repeated. After the second crop
winter sets in and there is not sufficient humidity. Therefore the pupa remains in the
cocoon in the diapauses state for about six months till the next onset of monsoon.

6.
7. Grainage- The process of Tasar egg making in lay mans term is called Grainage. It
involves storage of eggs, facilitating of male female coupling, washing cleaning of eggs
and disease checking.

8. Molt- A silkworm goes into molt phase five times in its life cycle of 30-35 days. During
this process it sheds its skin and does not eat. This is because there is enormous
enlargement in its size. During this process the old skin is shed and new skin comes up.

9. Ecorace- Due to agro climatic variations in the country various silkworm have adopted
to local conditions and have evolved into distinct ecoraces. For example daba,
modal,rally,laria are ecoraces of Tasar. Similarly in case of Mulberry ecoraces are
developed by Central Silk Board to get maximum productivity for a particular area.
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