Best Practices for Transporting and Preserving Mulberry Leaves

In sericulture, the quality of mulberry leaves at the time of feeding directly determines how well silkworms grow and how much silk they ultimately produce. But here’s the challenge – mulberry leaves (Morus alba) are living tissues that continue to respire and lose moisture even after being separated from the tree. From the moment a leaf is harvested, a countdown begins. If the leaf isn’t transported and stored properly, it wilts, loses nutrients, and becomes unfit for silkworm consumption. That’s why mastering the practices of leaf transportation and preservation is essential for every sericulturist aiming for healthy silkworms and high-quality cocoons.

Why leaf freshness matters for silkworm rearing 🔗

Mulberry leaves are the sole food source for the domesticated silkworm (Bombyx mori). Silkworms do not drink water separately – all the hydration they need comes from the moisture present in the leaves they eat. This means that wilted, dry, or deteriorated leaves don’t just reduce nutrition; they also deprive the worms of water, leading to stress, slower growth, and poor cocoon formation.

Fresh leaves are rich in proteins, carbohydrates, minerals, and moisture – all of which support the rapid growth that silkworms undergo, especially during late-age instars (4th and 5th stages), when they consume the largest quantities of food. Research published in Vegetos (Springer) confirms that leaf moisture and protein content directly influence larval weight, cocoon weight, shell weight, and overall silk yield. Feeding substandard leaves during this critical phase can reduce cocoon output significantly.

Additionally, leaves that begin to ferment or develop fungal growth after harvest can actively harm silkworms, causing digestive problems and increasing mortality. Proper handling from field to rearing house is therefore not optional – it’s a non-negotiable part of successful silk production.

Harvesting at the right time 🔗

Leaf transportation and preservation begin with the harvest itself. The time of day when you pick leaves has a major impact on how long they stay fresh.

Why cool hours are best 🔗

Leaves should be harvested during the early morning or late evening, when ambient temperatures are low. During these cooler hours, leaves contain their highest moisture levels. The overnight dew adds extra surface moisture, and the plant’s internal transpiration rate is minimal. As the day heats up, leaves lose water rapidly through transpiration, becoming less turgid and more prone to wilting after harvest.

Practically speaking, the recommended approach is to harvest about 70% of the day’s leaf requirement during the morning session and collect the remaining 30% in the evening. This strategy ensures that most of the leaves are picked when they are freshest and most moisture-rich.

Harvesting technique matters 🔗

How leaves are removed from the tree also affects their post-harvest longevity. Use sharp, clean cutting tools such as secateurs or pruning shears to make clean cuts. Pulling or tearing leaves by hand creates wounds on the leaf tissue, which accelerates moisture loss and opens entry points for bacteria. Handle leaves gently during collection, and avoid piling them too deep in the collection container – leaves at the bottom of a heavy pile get crushed, damaging their cellular structure.

For late-age silkworms, the shoot harvesting method (cutting entire branches) is often preferred because leaves attached to the branch stay fresh longer than individually picked leaves. The branch continues to supply some moisture to the leaves even after cutting, buying extra time before they wilt.

Transporting leaves from field to rearing house 🔗

Once harvested, mulberry leaves must reach the rearing house as quickly as possible. Ideally, leaves should arrive within 2-4 hours of harvesting. The longer the transit time, the greater the moisture loss and nutrient degradation.

Using baskets with wet gunny cloth 🔗

For small to medium quantities, the most common and effective method is to transport leaves in bamboo baskets covered with wet gunny cloth. Bamboo baskets are preferred over plastic containers for an important reason – they allow natural air circulation around the leaves, preventing the buildup of humidity that could trigger condensation and fungal growth. At the same time, the wet gunny cloth draped over the top creates a humid microenvironment that slows down moisture loss from the leaf surface.

The gunny cloth should be dampened with clean water and wrung out to remove excess dripping before placing it over the leaves. During the journey, if the cloth dries out, it needs to be re-moistened. This simple technique can make a substantial difference in the condition of leaves upon arrival.

Handling large quantities 🔗

When transporting larger volumes of leaves – common in commercial sericulture operations – the baskets may not suffice. In such cases, leaves are loaded onto carts or vehicles and covered with wet gunny cloth or polythene sheets. The polythene sheet acts as a barrier against wind and direct sunlight, both of which accelerate leaf drying. However, polythene does not allow air exchange, so it is best used for short-distance transport only. For longer journeys, wet gunny cloth remains preferable because it balances moisture retention with ventilation.

Regardless of the method, a few universal rules apply during transport. Keep leaves away from direct sunlight. Avoid stacking them too tightly – loose layering allows air to circulate and prevents heat buildup in the center of the pile. If possible, transport during cooler parts of the day (morning or evening) to reduce thermal stress on the leaves.

Minimizing transport distance 🔗

One of the simplest ways to preserve leaf quality during transportation is to reduce the distance between the mulberry garden and the rearing house. The National Sericulture Institute recommends building the rearing house close to the mulberry field to minimize transit time and reduce wilting. This is a planning-level decision, but it has a direct and ongoing impact on leaf quality throughout every rearing cycle.

Preserving leaves at the rearing house 🔗

Even after leaves arrive at the rearing house, they may not be fed to silkworms immediately. Depending on the feeding schedule, leaves might need to be stored for several hours – sometimes up to 24 hours. Proper storage conditions are critical during this period.

The leaf preservation room (leaf chamber) 🔗

A dedicated leaf preservation room, also called a leaf chamber, is a standard feature of well-planned silkworm rearing houses. This room serves one purpose: to maintain conditions that slow down the natural deterioration of harvested mulberry leaves.

The three key conditions to maintain in a leaf chamber are:

Cool temperature: The room should be kept between 20-25°C. Lower temperatures slow down the metabolic processes in harvested leaves, reducing the rate at which they consume their own stored sugars and proteins. High temperatures accelerate breakdown and can trigger fermentation, making leaves harmful to silkworms.

High humidity: Relative humidity in the storage room should ideally be between 85-90%. This prevents leaves from losing moisture to the surrounding air. Humidity can be maintained by placing water trays in the room, hanging damp cloths, or periodically misting the storage area.

Cleanliness: The storage room must be clean and regularly disinfected. Decaying organic matter harbors bacteria and fungi that can quickly spread to stored leaves, rendering them unsafe for silkworm feeding.

Covering leaves with wet gunny cloth during storage 🔗

Even inside the leaf chamber, leaves benefit from being covered with damp gunny cloth. This is the most widely used and effective preservation technique in sericulture. The wet cloth maintains a high-humidity layer directly around the leaves while still allowing some air exchange – unlike sealed polythene, which can trap gases and promote fermentation.

According to educational resources on moriculture, mulberry leaves should be kept in containers lined with clean, wet cotton cloth and covered with the same. The leaves should be heaped loosely and turned periodically to ensure proper aeration throughout the stored batch. Without turning, leaves in the center of a pile may heat up and start decomposing.

Storage duration limits 🔗

Under optimal conditions, mulberry leaves can maintain acceptable feeding quality for approximately 12-24 hours. Beyond that, nutritional degradation becomes significant, and the risk of spoilage increases. This is why sericulturists plan their harvest schedules to align closely with feeding times – harvesting just enough for the day’s needs rather than stockpiling large quantities.

For operations where fresh harvesting every day is not feasible, recent research from Springer has explored advanced methods such as nanoparticle-based preservation treatments that can extend leaf viability up to seven days. However, these technologies are still largely in the experimental stage and not yet widely adopted at the farm level.

Recognizing signs of leaf deterioration 🔗

Even with the best practices in place, it’s important to be able to identify when stored leaves are no longer suitable for feeding. Late-age silkworms are especially sensitive to poor leaf quality, and they will often refuse to eat deteriorated leaves altogether.

Color changes: Fresh mulberry leaves are a vibrant green. Yellowing, browning at the edges, or dark mushy spots indicate aging, dehydration, or microbial infection. Any discolored leaves should be removed immediately to prevent contamination of the rest of the batch.

Texture: Properly preserved leaves feel firm and slightly moist. If they are brittle, limp, or slimy, they have lost their nutritional value. Slimy texture in particular indicates bacterial breakdown.

Odor: Fresh mulberry leaves have a mild, characteristic aroma. A sour or foul smell signals fermentation or fungal activity. Such leaves must never be fed to silkworms, as they can cause digestive diseases and increase mortality.

Seasonal considerations 🔗

The season of the year significantly affects how challenging leaf preservation can be. During hot summer months, ambient temperatures are high, and leaves lose moisture much more rapidly after harvest. Sericulturists in tropical regions like India may need to harvest more frequently in smaller batches and pay extra attention to keeping transport containers and storage rooms cool.

During the monsoon season, excess ambient moisture can create the opposite problem – too much humidity encourages fungal growth on stored leaves. In this period, proper ventilation in the leaf chamber becomes especially important, and leaves should be checked more frequently for signs of mold.

In cooler weather (autumn or winter rearing in some regions), leaves naturally stay fresh longer, but growth rates of mulberry plants slow down, meaning fewer leaves are available. Planning harvests to match daily consumption becomes critical to avoid both shortages and waste.

Economic impact of proper leaf handling 🔗

Getting leaf transportation and preservation right has direct financial consequences. In a typical sericulture operation, improper handling can lead to 15-20% leaf wastage. Reducing this wastage through better practices directly translates to lower production costs and more efficient use of the mulberry garden’s output.

Beyond waste reduction, consistent leaf quality supports better silkworm health, which means lower mortality rates, more uniform cocoon production, and higher-grade silk that commands better market prices. The ICAR sericulture curriculum emphasizes leaf preservation as a core skill for this reason – it sits at the intersection of crop management and animal husbandry within sericulture.

Quick-reference checklist for leaf transportation and preservation 🔗

Harvest timing: Pick leaves during early morning or late evening when temperatures are cool and moisture is highest.

Cutting tools: Use sharp, clean secateurs or knives. Avoid tearing leaves by hand.

Transport containers: Use bamboo baskets for small quantities. Avoid sealed plastic bags.

Covering during transport: Drape wet gunny cloth over the leaves. For large quantities, wet gunny cloth or polythene sheets can be used.

Transport timing: Move leaves during cooler hours. Minimize distance and aim to reach the rearing house within 2-4 hours.

Storage conditions: Keep leaves in a clean, cool (20-25°C), humid (85-90% RH) leaf chamber.

Storage method: Spread leaves in loose layers, cover with damp cloth, and turn periodically for aeration.

Storage duration: Use stored leaves within 12-24 hours. Harvest fresh daily whenever possible.

Quality checks: Inspect stored leaves for color changes, texture loss, or off-odors before every feeding.

What do you think? If leaf quality drops so drastically within just 24 hours of harvest, how might sericulture operations in remote areas – where mulberry gardens are far from rearing houses – redesign their workflow to keep leaves fresh? And could emerging preservation technologies eventually make it practical to store leaves for several days without quality loss?

References

1. https://en.wikipedia.org/wiki/Morus_alba
2. https://link.springer.com/article/10.1007/s42535-024-00965-6
3. https://www.pandasilk.com/mulberry-silkworm-rearing-in-summer-autumn/
4. https://infonet-biovision.org/animal-species/mulberry-silkworm
5. https://indianagriexam.com/courses/b-sc-ag-vi-semester/lesson/rearing-house-and-rearing-appliances-of-mulberry-silkworm/
6. https://www.vedantu.com/chemistry/sericulture-and-moriculture
7. https://link.springer.com/article/10.1007/s44372-025-00130-6
8. https://ebook.icar.gov.in/index.php/ebook/pgmscseri_list