Best Practices for Mulberry Leaf Harvesting and Preservation in Sericulture

In sericulture, silk quality begins long before a silkworm spins its cocoon. It begins in the mulberry field, at the moment a leaf is plucked from the branch. For late-age silkworms – those in their fourth and fifth instars – mulberry leaves are the sole source of nutrition, and their freshness, moisture content, and nutritional integrity directly determine how well the silkworms grow and how much silk they ultimately produce. Getting the leaf from field to rearing house in peak condition is, therefore, not a minor detail – it is the foundation of a productive sericulture operation.

Why leaf quality matters most for late-age silkworms 🔗

Late-age silkworms are voracious feeders. During the fourth and fifth instars, silkworms consume the overwhelming majority of their total leaf intake for their entire life cycle. Their nutritional demands at this stage are immense, and any compromise in leaf quality – whether through wilting, fermentation, or contamination – can slow their growth, weaken their vitality, and reduce cocoon yield. Fresh, moisture-rich mulberry leaves supply the proteins, carbohydrates, and water that silkworms need for healthy development. Wilted or deteriorated leaves, on the other hand, are less digestible and can stress the larvae significantly.

What makes mulberry leaves particularly challenging to manage is that they are living tissue. Even after harvest, leaves continue to respire, consuming their own stored nutrients and losing water through transpiration. In warm or dry conditions, this deterioration accelerates rapidly. Rearing late-age silkworms under strict hygienic conditions, with proper attention to leaf freshness, is therefore essential to prevent disease and ensure healthy cocoon formation.

Harvesting mulberry leaves: timing is everything 🔗

The single most important decision in leaf management is when to harvest. Early morning harvesting is the established best practice in sericulture for well-grounded scientific reasons. During the cool morning hours, mulberry leaves retain their highest moisture content and maximum nutritional value. As temperatures rise through the day, leaves begin to lose water through transpiration, becoming less tender and less palatable for silkworms.

Morning harvesting also takes advantage of the natural dew that settles on leaves overnight, adding an extra layer of moisture that helps maintain freshness during the handling process. During peak summer months, harvesting between 6-8 AM or after 4 PM helps prevent wilting and preserves the leaf’s nutritional profile. Avoiding midday harvest is especially important in tropical and subtropical regions, where high temperatures can cause rapid deterioration within hours of plucking.

Leaf picking vs. shoot harvesting for late-age rearing 🔗

There are two primary harvesting methods used in mulberry sericulture: individual leaf picking and shoot or branch harvesting. Leaf picking involves hand-selecting individual mature leaves, which allows for precise quality control but is labor-intensive. In branch cutting, the entire branch is harvested, which is more cost-efficient and time-saving – and since the leaves remain attached to the branch, their freshness lasts considerably longer compared to individually detached leaves.

For late-age silkworms specifically, shoot harvesting – where the tops of shoots are clipped – is the recommended approach for 4th and 5th instar larvae. The shoots provide mature, nutritionally dense leaves that match the feeding requirements of this growth stage. Ideal leaves come from shoots that are roughly 55-65 days old, representing the best balance between protein content and digestibility. Leaves that are too young lack sufficient nutrients, while overly mature leaves can be tough and harder for silkworms to process efficiently.

Transporting mulberry leaves without losing freshness 🔗

Once harvested, leaves face their first major challenge: the journey from the field to the rearing house. The choice of transport container and method plays a significant role in how much nutritional value survives the trip.

Bamboo baskets: the preferred transport container 🔗

Bamboo baskets are the standard and most effective container for transporting mulberry leaves. Their breathable, open-weave structure allows air to circulate around the leaves, which prevents the buildup of heat and moisture that could trigger fermentation or encourage fungal growth. Unlike plastic containers, which trap humidity and accelerate microbial activity, bamboo creates a natural microenvironment that keeps leaves fresh without making them waterlogged. The natural fibers also absorb small amounts of excess moisture without completely drying the leaves out – maintaining the critical balance that late-age silkworms depend on.

Covering with wet gunny cloth 🔗

Leaf-filled bamboo baskets should be covered with wet gunny cloth during transport. The damp fabric serves two functions: it creates a humid microclimate around the leaves that slows water loss, and it shields the leaves from direct sunlight, which can cause rapid wilting. For journeys longer than 30 minutes by tractor or head load, covering the leaves with wet gunny cloth is essential to reduce moisture loss.

The key is to keep the gunny cloth damp, not soaking wet. Excess moisture can lead to leaf deterioration just as readily as dryness – the goal is to maintain humidity, not saturate the leaves. A cloth that is wrung out after wetting, leaving it moist but not dripping, is ideal for this purpose.

Storing and preserving mulberry leaves before feeding 🔗

When harvested leaves cannot be fed to silkworms immediately, proper storage becomes critical. The storage room functions as the final line of defense against leaf deterioration, and its conditions directly affect how long mulberry leaves remain nutritious and acceptable to late-age silkworms.

Keeping the storage room clean and disinfected 🔗

The storage room must be kept clean and thoroughly disinfected before leaves are brought in. Mulberry leaves are organic material, and any pre-existing bacterial or fungal contamination in the room can quickly spread to the stored leaves. Pathogens can survive in rearing environments for extended periods and cause serious disease in silkworms if not eliminated beforehand. Regular disinfection with appropriate agents – and ensuring no residual organic matter from previous batches is left behind – is non-negotiable before each storage cycle.

Maintaining high humidity and low temperature 🔗

Harvested leaves and shoots should be preserved in a clean and disinfected room where high humidity and low temperature are maintained. These two conditions work together to slow the metabolic processes that degrade leaves after harvest. High humidity reduces water loss through transpiration, keeping leaves turgid and fresh. Low temperature slows enzymatic breakdown and inhibits microbial growth. Together, they extend the window during which leaves remain nutritious and palatable.

Importantly, humidity management in storage differs from silkworm rearing conditions. Large silkworms thrive at around 75% relative humidity, whereas the leaf storage room should be maintained at higher humidity to preserve the moisture content of the leaves themselves. Freshly harvested leaves should generally be used within 24-48 hours of storage to maintain their optimal nutritional value and prevent bacterial or fungal buildup.

Preserving mulberry shoots in a vertical position 🔗

When mulberry shoots are harvested rather than individual leaves, a specific storage practice applies. Shoots should be stored upright, in a vertical position, and covered with wet cloths. This method mirrors the natural orientation of the shoot on the plant, which helps the leaves maintain their shape and reduces physical damage from piling. Vertical positioning also allows for better air circulation between shoots, reducing the risk of heat buildup that can occur when wet plant material is stacked horizontally in bulk.

Covering the vertically placed shoots with wet cloth extends the same humidity-preserving logic used during transport – slowing moisture loss and keeping the leaf surface from drying and curling, which makes leaves unpalatable and harder for silkworms to consume efficiently.

How poor leaf handling affects silk production 🔗

The downstream consequences of inadequate leaf management are significant. Wilted or fermented leaves fed to late-age silkworms can cause digestive stress, slower growth, higher larval mortality, and ultimately smaller or lower-quality cocoons. The harvested leaf should be immediately transferred to the rearing house without losing moisture content – every hour of delay without proper precautions reduces the leaf’s value as a feed material.

Studies in sericulture practice have shown that proper leaf handling – from timing of harvest to storage conditions – can meaningfully improve cocoon production. The economics are straightforward: better leaves mean healthier silkworms, higher cocoon yields, and better-quality silk fiber that commands stronger market prices. For small-scale and commercial sericulturists alike, investing attention and effort into leaf management is one of the most cost-effective steps toward a more productive operation.

Seasonal adjustments in leaf handling 🔗

Leaf management practices must adapt to the season. During hot summer months, leaves deteriorate more rapidly, requiring smaller, more frequent harvests and extra vigilance about temperature in the storage room. In the monsoon season, high ambient humidity is beneficial for storage, but excessive moisture combined with warmth can promote fungal growth on leaves – careful ventilation and more frequent inspection become necessary. During winter, while cooler temperatures slow deterioration, they can also make leaves stiffer and harder for silkworms to eat; allowing leaves to warm slightly to room temperature before feeding can help maintain palatability without sacrificing freshness.

Atmospheric humidity in the range of 65-80 percent is ideal for mulberry plant growth, and regions that fall outside this range during certain seasons require adjusted harvesting schedules to ensure consistent leaf quality throughout the rearing cycles.

What do you think? How might sericulturists in regions with extreme summer temperatures or heavy monsoon conditions adapt their leaf harvesting and storage routines to maintain consistent leaf quality? And do you think small-scale farmers have the resources to implement optimum storage conditions – or are there practical, low-cost alternatives that could achieve similar results?

References

1. https://www.fao.org/4/x9895e/x9895e04.htm
2. https://www.pandasilk.com/temperature-humidity-requirements-for-mulberry-silkworm-rearing/
3. https://infonet-biovision.org/animal-species/mulberry-silkworm
4. https://www.numberanalytics.com/blog/science-behind-sericulture
5. https://www.vedantu.com/biology/moriculture
6. https://indiaagronet.com/Moriculture/
7. https://silks.csb.gov.in/anjaw/wp-content/themes/Common_District/trs-frame.html