Pruning and Size Management Techniques for Tasar Food Plants

Tasar silk – one of India’s most valued wild silks – depends entirely on the quality of leaves produced by its host plants. Species like Terminalia arjuna (Arjun), Terminalia tomentosa (Asan), and Shorea robusta (Sal) are the primary food plants of the tropical tasar silkworm (Antheraea mylitta). Left unmanaged, these trees can grow over 20-25 metres tall, making leaf harvest nearly impossible and silkworm supervision extremely difficult. That is why pruning and plant size management form the backbone of productive tasar sericulture.

Why size management matters in tasar cultivation 🔗

In the wild, tasar food plants grow as tall, irregularly distributed forest trees. According to the Central Silk Board, plants approximately 2-3 metres tall with rich foliage and a well-spread crown are ideal for effective silkworm rearing. Without deliberate size control, several problems arise.

First, tall trees make it extremely hard to supervise larvae during outdoor rearing. Tasar silkworms are reared on open trees – not indoors – so workers must be able to see and access every branch. Second, unmanaged trees tend to develop sparse, coarse leaves at the top of a tall canopy rather than the tender, nutritious foliage that silkworms need. Third, tall, dense canopies restrict air circulation, creating humid micro-environments that encourage fungal diseases and pest infestations.

Proper size management addresses all of these issues. It keeps plants at a harvestable height, promotes the growth of multiple lateral branches (which means more leaf surface area), improves air and light penetration through the canopy, and channels the plant’s energy toward producing young, tender shoots instead of vertical growth.

Initial training: the first few years 🔗

Plant size management begins right from the nursery and transplanting stage. Tasar food plant saplings are typically raised from seeds in nurseries and then transplanted to the field. The spacing between plants depends on the plantation type. Economic plantations of Terminalia arjuna use close spacing of about 1.2 × 1.2 metres, while regular block plantations follow wider spacing of around 3-4 metres or more.

Light pruning and thinning 🔗

During the first 2-3 years after transplanting, the goal is to let the plant establish a strong root system and a sturdy framework of branches. Pruning at this stage is kept minimal – just enough to shape the young plant and remove any problems early. This initial training involves:

Removing weak or competing shoots: When a young sapling develops forked growth (which often happens after frost damage), the weaker shoot is pruned away so that the stronger one can develop into a well-defined main stem. Weeding and frost protection are also essential during these early years, as frost damage frequently causes unwanted forking in species like T. arjuna.

Thinning out crowded branches: If too many branches emerge from the same point, some are thinned out so the remaining ones have room to grow strong. This prevents the development of narrow-angled, weak branch junctions that could split later under the weight of foliage and silkworm cocoons.

Removing dead or diseased wood: Any branches showing signs of disease, pest damage, or dieback are removed promptly to prevent infection from spreading.

The key principle during this phase is restraint. Heavy pruning on a young plant diverts too much energy toward wound healing and regrowth, slowing down the establishment of the root system. Light, selective cuts are all that is needed.

The open centre system: the core pruning method 🔗

Once tasar food plants are 4-5 years old and well-established, it is time to adopt a more structured pruning approach. This is where the open centre system (also called the open-centre or vase system) comes into play. It is widely regarded as the most effective training method for tasar plantations.

What is the open centre system? 🔗

The open centre system creates a bowl-shaped or vase-shaped tree architecture. The central upward-growing leader branch is removed, and instead, 3-4 strong lateral (outward-growing) branches are encouraged to form the primary scaffold of the tree. These primary branches then develop secondary and tertiary branches, resulting in a wide, spreading canopy with an open interior.

The Central Silk Board recognises three common training systems for tasar food plants – the central leader system, the open centre system, and the modified leader system. Among these, the modified leader system (where the central axis is not allowed to grow indefinitely) is recommended for economic plantations. The open centre system, however, remains the go-to method for many sericulturists because of its advantages in leaf quality and ease of rearing operations.

How it is done 🔗

Implementing the open centre system involves a few clear steps:

Removing the central leader: The dominant upward-growing branch is cut back to a point where 3-4 well-spaced lateral branches emerge. This forces the tree’s energy outward rather than upward.

Selecting scaffold branches: Choose 3-4 strong lateral branches that are evenly distributed around the trunk and spaced apart vertically by at least 10-15 cm. These become the primary framework. They should grow outward and slightly upward – not steeply vertical and not drooping.

Maintaining the open centre: Any new shoots that grow inward toward the centre of the canopy, or straight up as replacement leaders, are removed regularly. The centre of the tree must remain open to allow sunlight and air to reach the inner canopy.

Controlling height: As the scaffold branches grow, their tips are periodically pruned to keep the overall plant height at 2-3 metres – the ideal range for tasar rearing operations.

Why this shape works for tasar 🔗

There are specific reasons why the open centre shape benefits tasar sericulture. Sunlit leaves are generally more nutritious and more easily digested by silkworms than shaded ones. By opening up the canopy, this system ensures that most leaves receive direct or filtered sunlight. Better air circulation inside the canopy also reduces humidity build-up, which in turn lowers the risk of fungal diseases – a serious concern in the humid tropical regions where tasar is reared.

From a practical standpoint, a wide, low canopy at 2-3 metres makes it far easier for rearers to brush (place) young larvae onto leaves, monitor their health, transfer them between plants, and collect cocoons – all operations that need to happen regularly during the rearing season.

Pollarding: a complementary size control technique 🔗

In addition to the open centre pruning system, pollarding is another important technique used to manage tasar food plant size, especially in natural or semi-wild plantations.

Pollarding involves cutting the tree back heavily – typically 1-2 metres above the ground – so that it regenerates a dense cluster of new shoots from the cut points. These new shoots produce abundant tender foliage, which is exactly what young tasar silkworms prefer. In natural plantations, pollarding is recommended during March and April (before the rearing season) and is repeated every 3-4 years.

Pollarding is especially useful for trees that have been allowed to grow too tall or have become unmanageable through neglect. It essentially resets the plant’s above-ground structure and triggers vigorous regrowth. Research in tasar-producing regions has shown that regular pruning and pollarding help generate secondary and tertiary branches, besides producing biomass that can be used as timber, fuel, fodder, or raw material for vermicompost.

However, pollarding is a drastic technique and should not be done too frequently, as it can weaken the tree’s root reserves over time. It works best as a periodic corrective measure combined with ongoing lighter pruning in the intervening years.

Timing and seasonal considerations 🔗

Getting the timing right is critical for successful pruning of tasar food plants. The best period for major pruning and pollarding is late winter to early spring – specifically March and April in most tasar-growing regions of India. This timing works because:

The trees are dormant or semi-dormant: Pruning during dormancy minimises sap loss and reduces stress on the plant. The tree can redirect its stored energy into producing fresh shoots once the growing season begins.

New growth coincides with rearing season: Tasar silkworm rearing typically begins in June-July (summer crop). By pruning in March-April, the new tender foliage is ready just when the early instar larvae need it most.

Disease risk is lower: Dry, mild weather in late winter reduces the chance of fungal pathogens entering through fresh pruning wounds. Pruning during the monsoon season should be avoided because wet conditions promote infection.

Light maintenance pruning – removing water sprouts, crossing branches, or diseased wood – can be carried out throughout the year as needed, but heavy structural pruning should be restricted to the dormant window.

Practical pruning techniques 🔗

Proper technique matters as much as proper timing. Careless cuts can invite disease and weaken the plant, undoing the benefits of pruning.

Making the right cut 🔗

Always cut just outside the branch collar – the slightly swollen area where a branch meets the trunk or parent limb. The branch collar contains specialised cells that help the wound heal (compartmentalise). Cutting flush with the trunk destroys this natural healing zone, while leaving a long stub creates a dead piece of wood that becomes a disease entry point.

For larger branches, a three-cut method prevents the bark from tearing as the branch falls. Make the first cut on the underside of the branch about 30 cm from the trunk (cutting only partway through). Make the second cut from the top, slightly further out, to let the branch drop cleanly. Finally, make the third clean cut just outside the branch collar to remove the remaining stub.

Tool hygiene 🔗

Since tasar food plants are susceptible to various diseases – including leaf rust, leaf spot, and wilt – pruning tools (secateurs, loppers, saws) should be cleaned and disinfected between trees. A simple wipe with a cloth soaked in rubbing alcohol or a dilute bleach solution is effective. This basic step prevents the accidental spread of pathogens from an infected tree to healthy ones.

Post-pruning care 🔗

After pruning, it is helpful to apply a wound sealant or a paste of copper fungicide on larger cuts (above 3-4 cm diameter) to minimise disease entry. Plants should also be given a dose of farmyard manure or compost to support the energy demands of regrowth. Proper manure application alongside pruning is an established part of tasar plantation management, especially in government and private plantations.

How pruning maximises leaf yield and quality 🔗

The entire purpose of these pruning and size management efforts is to produce the best possible leaves for tasar silkworm feeding. Here is how pruning directly improves leaf output:

Stimulates new shoot growth: Every pruning cut triggers the growth of new lateral shoots from dormant buds below the cut. These young shoots bear tender, nutrient-rich leaves – exactly the kind that early instar tasar larvae thrive on. Younger larvae in particular need soft, juicy foliage; reddish or coarse old leaves are actually harmful to them.

Increases leaf surface area per plant: A well-pruned plant with multiple lateral branches produces significantly more leaves than a tall, single-stemmed tree. High-density economic plantations of T. arjuna with close spacing and regular pruning can yield over 17 metric tonnes of foliage per hectare.

Improves leaf nutritional quality: Leaves on sun-exposed branches have higher nutritional value and better digestibility for silkworms than shaded leaves. The open centre system ensures uniform light distribution, so leaves across the canopy are of consistently better quality.

Reduces pest and disease losses: By removing diseased branches and improving air flow, pruning lowers the incidence of fungal diseases and makes it easier to spot and manage pest problems early. This protects not just the plant but also the silkworm population being reared on it.

Common mistakes to avoid 🔗

Even experienced growers sometimes make errors with pruning. A few common mistakes in tasar food plant management include:

Over-pruning young plants: Removing too much foliage from a newly transplanted sapling weakens its root development and delays the time it takes to become rearing-ready. Stick to light, selective cuts during the first 3-4 years.

Pruning during wet weather: Making cuts during the rainy season significantly increases the chance of fungal and bacterial infections. Always schedule heavy pruning during dry weather in March-April.

Neglecting follow-up maintenance: A single round of open centre pruning is not enough. New water sprouts and inward-growing branches will continuously attempt to fill the centre. Regular follow-up trimming (at least once or twice a year) is needed to maintain the desired shape.

Ignoring tool hygiene: Moving from tree to tree with dirty tools spreads diseases like leaf spot and wilt through the entire plantation. Disinfecting tools takes just a moment and can save an entire stand of food plants.

Using the same plants for consecutive rearing crops: According to the Central Silk Board’s rearing guidelines, food plant bushes should not be used for two successive crops in a year. Rotating between different sets of plants gives each group time to recover and regenerate healthy foliage.

Integrating pruning with overall plantation management 🔗

Pruning does not work in isolation. For the best results, it needs to be integrated with other cultural practices in the tasar plantation. Regular weeding around the base of each plant reduces competition for nutrients and water, and also removes potential habitats for pests. Soil management – including application of farmyard manure, compost, bone meal, and other organic inputs at the time of planting and after pruning – keeps the soil fertile enough to support vigorous regrowth.

In natural forest settings where tasar rearing takes place on existing wild trees, the approach shifts toward periodic pollarding and gradual enrichment of the forest with additional food plant saplings. The aim is the same – manageable plant size, abundant tender foliage, and reduced disease pressure – but the methods need to accommodate the constraints of working with established, wild-growing trees.

What do you think? If tasar silkworms naturally feed on tall forest trees, do you think systematic pruning and plantation-based rearing could eventually replace traditional forest-based tasar culture entirely – or will both methods always need to coexist?

References

1. https://sericulture.assam.gov.in/portlet-innerpage/food-plants-of-tasar-silkworm
2. https://silks.csb.gov.in/aizawl/tasar-food-plant-production-technology/
3. https://silks.csb.gov.in/balaghat/food-plant-production-technology-of-tropical-tasar/
4. https://apps.worldagroforestry.org/treedb2/speciesprofile.php?Spid=18136
5. https://www.researchgate.net/publication/373603216_INTEGRATED_FARMING_SYSTEM-A_KEY_TO_SUSTAINABLE_LIVELIHOOD_IN_TASAR_SERICULTURE
6. https://hbmahesh.weebly.com/uploads/3/4/2/2/3422804/non_mulberry_food_plant_cultivation..pdf
7. https://silks.csb.gov.in/keonjhar/rearing-of-tasar-silkworm/