Comprehensive Guide to Tasar Silkworm Rearing in Non-Mulberry Sericulture

Tasar silk holds a unique place in India’s sericulture landscape. Unlike mulberry silk, which is produced in controlled indoor settings, tasar silk comes from the wild semi-domesticated silkworm Antheraea mylitta, reared openly in forest environments. According to the Central Silk Board, tasar silk is characterised by its distinctive copperish colour, coarse texture, and natural lustre – qualities that make it irreplaceable in Indian handloom traditions. The rearing process, however, is far more complex and labour-intensive than conventional sericulture. It involves site selection in natural forests, careful egg incubation, two distinct rearing phases, and attentive cocoon harvesting – all carried out in the open, under the mercy of weather, predators, and disease. Understanding this process from start to finish is essential for anyone serious about non-mulberry sericulture.

What makes tasar sericulture different? 🔗

Antheraea mylitta is a polyphagous, semi-domesticated wild silkworm – meaning it feeds on multiple plant species and cannot be entirely confined or controlled like the mulberry silkworm. Its life cycle passes through four stages: egg, larva, pupa, and adult. The adult moths do not feed at all; only the larvae are active feeders, and they feed voraciously. There are 44 recognised eco-races of A. mylitta distributed across different forest zones of India, each adapted to local climatic and ecological conditions.

Tasar silk production supports nearly 100,000 tribal families across central and eastern India, primarily in Jharkhand, Odisha, Chhattisgarh, West Bengal, and Madhya Pradesh. These communities have practised tasar culture as a livelihood and cultural heritage for generations. The entire rearing cycle – from brushing the newly hatched larvae to harvesting the finished cocoons – spans roughly six to ten weeks and demands consistent attention around the clock.

Primary food plants: sal, asan, and arjun 🔗

The success of any tasar crop begins with the food plant. The three primary host plants for tasar silkworms are Shorea robusta (Sal), Terminalia tomentosa (Asan), and Terminalia arjuna (Arjun). Secondary plants like Zizyphus jujuba (Ber) and Melastoma malabathricum are also used but are less preferred. Among the primaries, Asan and Arjun are especially important for commercial rearing, while Sal forests are often used for wild collection and supplementary rearing.

Leaf quality is directly tied to larval health. Young larvae thrive on tender, juicy leaves, while reddish or pale green foliage is harmful to them. Later instars require medium to mature leaves. This shift in leaf preference across instars is one reason tasar rearing is managed across multiple tree types and locations. The nutritional status of the food plant plays a pivotal role in the silkworm’s life cycle and its reproductive potential, which is why plant management – including soil nutrition, pruning, and irrigation – is a fundamental part of tasar sericulture.

Rearing site preparation 🔗

Choosing and preparing the rearing site correctly can be the difference between a productive crop and a failed one. Low-lying areas prone to waterlogging should be avoided. Fairly thick patches of food plants standing 3 to 3.5 metres tall are considered ideal. Waterlogging raises relative humidity to harmful levels, and the accumulation of dead larvae and excreta in such conditions can rapidly pollute the rearing environment and trigger disease outbreaks.

Before rearing begins, the site and surrounding area must be cleared of weeds. Ant nests and other insects on the bushes should be removed, and the same bushes should not be used for two successive crops in a year. Ants – especially weaver ants – are among the most damaging predators of young tasar larvae. Major predatory wasps such as Polistes olivaceus and P. stigma also pose a significant threat in tasar-growing regions of Jharkhand, Odisha, and West Bengal. Clearing and disinfecting the site beforehand reduces these risks considerably.

Egg incubation and brushing 🔗

Tasar rearing begins with Disease Free Layings (DFLs) – egg batches certified to be free of pebrine and other transmissible diseases. A single female tasar moth lays approximately 150 to 200 eggs over a period of about 48 hours. These eggs are oval, dorso-ventrally flattened, and are treated with 2% formalin, washed, dried, and then allowed to hatch. Larvae emerge in about ten days under normal conditions.

Brushing is the process of transferring newly hatched larvae to the host plant. The traditional method of tying leaf cups containing eggs directly onto bushes for hatching exposes both developing embryos and newly hatched larvae to fluctuating temperature, humidity, heavy rain, and storms – resulting in poor hatchability and heavy larval losses. The improved method involves hatching the eggs in a controlled space and then placing the hatchlings on prepared food plant twigs. A small twig is placed over each batch of newly hatched larvae, which are then distributed uniformly across the bushes. Only one day’s hatchings should be used per batch to avoid overcrowding and uneven development.

Chawki rearing: protecting the youngest larvae 🔗

The early larval instars – typically the first to third – are the most vulnerable stage in tasar rearing. This phase is known as chawki rearing. After brushing, young larvae are transferred to a chawki garden under a nylon net cover to protect them from predators and unfavourable environmental conditions.

Rearing up to the third instar is conducted on an economic plantation – ideally maintained food plant plots – preferably under nylon netting. The medium size and regularity of such plantations allow for more efficient management and supervision while minimising larval loss. Under traditional open-rearing methods, first instar losses alone typically reach 30%, with additional losses from disease and predators bringing total early-instar mortality to 40-50%. In contrast, controlled chawki rearing under netting can reduce first-instar losses to as low as 5%.

When climatic conditions are particularly unfavourable – continuous rain, stormy winds, or extreme temperatures – indoor rearing may be adopted as an alternative, with twigs placed in polythene bags supported by a bamboo frame. The enclosed setup must be opened daily for about 15 minutes for cleaning and aeration. Special care must be taken to remove the enclosure as soon as larvae begin to settle for moulting, as difficult ecdysis inside the bag can cause heavy mortality.

Late-age rearing: transferring to forest trees 🔗

Once the larvae have completed their second or third moult and entered the fourth instar, they are strong enough to be transferred from the chawki garden to the main forest or block plantation. This is the late-age rearing phase, covering the fourth and fifth instars. The transfer is done by cutting off small branches bearing larvae and attaching them to unused food plants. Ideally, this transfer should be done only once or twice to minimise stress and handling damage to the larvae.

To save time and labour, chawki rearing centres should be situated as close to the forest as possible. During late-age rearing, the larvae feed intensively and can defoliate trees rapidly. The fifth instar larva is green in colour with violet tubercles distributed over the body, and displays a prominent brown and yellowish lateral line on either side. At this stage, larvae are also more resistant to disease than in the early instars, but remain vulnerable to pests, predators, and adverse weather.

Daily monitoring is essential. Dead larvae hanging on the bush or fallen to the ground must be collected every morning and evening. A sample should be examined for microsporidiosis. All dead larvae must be buried outside the rearing site, and those showing symptoms of disease should be reared separately or destroyed along with the foliage they were on. Rearing appliances and field workers’ hands should be disinfected with antiseptic solution after every contact with the larvae.

Moulting management 🔗

Tasar larvae undergo four moults across five instar stages during their larval period, which lasts approximately 30 to 35 days in summer and longer in winter. Each moult marks the transition from one instar to the next, and each requires careful management to prevent mortality.

The most important rule during moulting is: do not disturb the larvae. Moulting larvae are in a temporarily immobile and highly vulnerable state. Moving, handling, or jolting them during ecdysis can cause incomplete skin shedding, resulting in deformity or death. Feeding should be suspended or substantially reduced while the majority of the population is moulting. Once most larvae have successfully shed their skin and resumed active feeding, normal feeding can be restored. Spinning larvae also need special attention at this stage, as they require adequate foliage to form the hammock for proper cocoon construction.

Cocoon formation and harvesting 🔗

When the fifth instar larva is fully mature, it stops feeding and begins the process of spinning its cocoon. Cocoon formation begins with gut purging – the larva expels its gut contents through a series of abdominal contractions. It then enters a wandering phase before settling on a suitable site to pupate. The first phase of cocoon construction involves building a silk scaffold between the leaves of the host plant and producing a stalk or peduncle that attaches the cocoon to a twig or leaf petiole. The larva then weaves loops of silk in figure-of-eight movements, building one end of the cocoon before turning 180° to form the other. The entire process takes about two days.

The finished tasar cocoon is tough, made from a single silk thread measuring approximately 1,000 metres, and has a large peduncle that fits into the branch of the host plant. The wall hardens and turns yellowish-brown as the silk protein sericin undergoes cross-linking and tanning.

Cocoons should be harvested six to seven days after spinning is complete – by which point pupation is fully established inside. Harvesting too early risks damaging an incompletely formed cocoon, while waiting too long reduces cocoon quality.

Sorting cocoons: commercial use vs. seed production 🔗

Not every harvested cocoon goes to the reeling unit. After harvest, cocoons are carefully sorted and graded. Well-formed, firm cocoons with intact peduncles and no signs of disease or pest damage are separated into two categories: those selected for seed production (used to breed the next generation of moths and produce DFLs) and those designated for commercial reeling into raw silk yarn.

The first crop, raised during July-August, is typically the seed crop, while the second crop reared during September-October serves as the commercial crop. Cocoons from the commercial crop that are damaged, flimsy, double, or irregular in size are set aside for spun silk production rather than reeling. Waste outer layers, damaged cocoons, and peduncles are teased and spun on an earthen mutka, producing a coarser yarn known as katia matka, which is valued in its own right for rustic handloom fabrics.

Under improved rearing conditions, yields can reach 45 to 50 cocoons per DFL, compared to just 15 to 20 cocoons under traditional unmanaged methods. This significant difference in output underscores the value of scientific rearing practices – from chawki protection to disease management to proper site preparation – over the older habit of simply releasing larvae on scattered forest trees and hoping for the best.

Challenges and the road ahead 🔗

Tasar silk production has stagnated and even declined in recent years despite increasing demand. The primary reasons are the traditional practice of rearing on tall trees in natural habitat, which exposes larvae to predators, parasites, and diseases as well as unpredictable weather. Several eco-races are also under threat due to deforestation and the unchecked collection of cocoons from wild populations.

Improving yields requires a shift from purely traditional practices toward more structured interventions: establishing chawki rearing centres close to forests, promoting controlled brushing techniques, adopting nylon net protection during early instars, and ensuring systematic disease monitoring throughout the crop. Organisations like the Tasar Development Foundation, working alongside the Central Silk Board, have introduced private grainage units and community resource persons to help tribal rearers produce their own quality DFLs and practice more scientific rearing methods – a step that directly improves both cocoon yield and farmer income.

What do you think? With tasar silk production still largely dependent on tribal communities rearing silkworms in open forest environments, how can improved chawki rearing techniques be made more accessible at the grassroots level? And given the growing threats of deforestation and climate variability, what role should host plant conservation play in the long-term sustainability of tasar sericulture?

References

1. https://csb.gov.in/
2. https://en.wikipedia.org/wiki/Antheraea_paphia
3. https://link.springer.com/chapter/10.1007/978-981-10-3304-9_10
4. https://tdf.org.in/tasar-silk.html
5. https://sericulture.assam.gov.in/portlet-innerpage/food-plants-of-tasar-silkworm
6. https://silks.csb.gov.in/keonjhar/rearing-of-tasar-silkworm/
7. https://www.plantarchives.org/SI%20VSOG/2.pdf
8. https://www.researchgate.net/figure/Rearing-of-tropical-tasar-silkworm-A-mylitta-D-showing-a-Host-plant-T-tomentosa_fig1_310773553
9. http://celkau.in/Agrienterprises/enerprise/26.%20Sericulture/8.%20Tasar%20Silkworm%20Culture.pdf
10. https://www.taylorfrancis.com/chapters/mono/10.1201/9781003197393-27/chawki-rearing-methods-tasar-silkworm-elumalai-mohan-raj-ramamoorthy-mohan-poovizhiraja
11. https://www.indianforester.co.in/index.php/indianforester/article/view/12846
12. https://www.shivajicollege.ac.in/sPanel/uploads/econtent/d7087d76d2106f258390ba1ec46c7e1c.pdf