Influence of Psoralea corylifolia on Economic Traits of Silkworm, Bombyx mori. L

Sericulture is a vital agro-based industry that significantly supports rural employment and the textile economy, especially in Asian countries. The domesticated silkworm B. mori is widely used for commercial silk production due to its ability to produce superior-quality silk fibers. The success of sericulture largely depends on larval growth performance and cocoon quality. Since silkworms are reared on mulberry leaves, silk yield is directly influenced by larval development on mulberry (Bhattacharyya et al., 2016). Larval growth is affected by environmental conditions, feed quality, and rearing practices, with nutrition playing a key role in determining survival, cocoon traits, and silk quality. Being monophagous, silkworms rely solely on mulberry leaves for essential nutrients; however, variations in leaf quality can significantly impact productivity (Pakhale et al., 2014). In recent years, plant-based supplements and herbal extracts have gained attention as natural biostimulants to enhance silkworm performance. The growth and physiology of B.mori are highly dependent on diet composition, which directly influences larval development, silk gland activity, and cocoon formation (Rahmathulla, 2012). Nutritional and environmental factors also regulate silk gland function and silk protein synthesis (Sehnal, 1990). Medicinal plants are rich in bioactive compounds such as flavonoids, alkaloids, phenolics, terpenoids, and essential oils, which possess antioxidant and antimicrobial properties (Cowan, 1999). These compounds can enhance digestion, nutrient absorption, immunity, and overall physiological efficiency, thereby improving silkworm growth and productivity (Rahmathulla, 2012).

The experiment was conducted in the silkworm rearing house of the Department of Sericulture, Forest College and Research Institute, Mettupalayam, Tamil Nadu, India, under controlled environmental conditions of temperature (25 ± 2 °C) and relative humidity (70–80%), which are optimum for rearing B.mori. Seeds of P.corylifolia were cultivated under field conditions, and fully matured plants were harvested. The plant materials were washed thoroughly, shade-dried for about one week to preserve bioactive compounds, and ground into coarse powder. A 25 g powder sample was subjected to Soxhlet extraction with hexane at a 1:10 (w/v) ratio. The extract was filtered, concentrated on a rotary evaporator at 40 °C, and stored at 5 °C for further use (Nafiu et al., 2017). The experiment consisted of two controls and six treatments with different concentrations (1, 2, and 4 ml/L) and feeding schedules. Each treatment included 50 larvae with three replications and was arranged in a completely randomized design (CRD) (Nair et al., 2010). Treated mulberry leaves were air-dried before feeding. Silkworm larvae were reared under standard conditions with proper hygiene, spacing, and feeding practices. During the fifth instar, larvae were fed with treated leaves according to the treatment schedule (Soliman, 2025). After completion of larval development, mature larvae were mounted to form cocoons, and cocoons were harvested for further analysis (Sujatha et al., 2015). The collected data were subjected to ANOVA using GRAPES software to determine significant differences among treatments (Konwar et al., 2023). The experimental treatments were arranged as shown in Table 1.

                                  Table 1. Experimental treatments used in the study

Observations Recorded

To evaluate the influence of P. corylifolia extract, both biological and commercial parameters were recorded. For each treatment, 10 larvae, 5 cocoons, 5 pupae, and 5 shells were randomly selected per replication for observation. Larval parameters included larval weight, larval duration, disease incidence (%), and survivability (%). Larval weight was measured during the fifth instar, and duration was recorded based on the time taken for completion of larval development (Soliman, 2025). After the cocoon harvest, cocoon weight, pupal weight, and shell weight were recorded using a digital balance. Shell ratio was calculated using the standard formula: Shell Ratio (%) = (Shell Weight / Cocoon Weight) × 100 (Central Silk Board, 2015). The effective rate of rearing (ERR) was calculated from the number of good cocoons obtained, and defective cocoons were identified by abnormalities such as double, flimsy, or pierced cocoons (FAO, 1990). Disease incidence was recorded as the percentage of infected larvae. Reeling parameters, such as filament length and weight, were measured, and denier was calculated from these measurements. Raw silk percentage was also estimated to assess silk recovery (Central Silk Technological Research Institute, 2017).

The influence of Psoralea leaf extract on the growth, cocoon characteristics, and reeling performance of B.mori is illustrated through bar graphs for larval (Figure 1) and cocoon traits (Figure 2), while reeling parameters are presented in Table 2. The results indicate that both the concentration and the timing of application had significant effects on silkworm growth, cocoon quality, and reeling performance.

Figure 1. Illustrates the Larval Parameters of Silkworm B.mori

Larval Performance

Larval parameters showed a clear improvement under treated conditions compared to controls. Among all treatments, the 2 ml/L extract applied on the 2nd and 4th days recorded the highest larval weight (18.20 g), indicating enhanced nutrient assimilation and improved physiological efficiency. This improvement may be attributed to the presence of bioactive compounds, including flavonoids, coumarins, and phenolics, in P. corylifolia, which are known to stimulate digestion and metabolic activity (Cowan, 1999; Rahmathulla, 2012). Similar enhancement in larval growth due to botanical supplementation has been reported by Rafiq et al., (2020). Larval duration remained relatively stable across treatments, with only a slight extension of less than one day. This marginal increase may be associated with prolonged feeding activity and improved nutrient utilization, allowing larvae to accumulate greater biomass before pupation (Nair et al., 2003). Importantly, this extension did not negatively affect cocoon formation, indicating that the treatments supported sustained physiological development. A significant reduction in disease incidence was observed in treated groups. The lowest disease incidence (3.20%) was recorded at 4 ml/L (5th–7th day), followed by 2 ml/L (2nd & 4th day) at 4.80%, compared with higher levels in the control groups. This clearly demonstrates the antimicrobial properties of P. corylifolia, which contains compounds such as psoralen and bakuchiol (Khushboo et al., 2010). Although higher concentrations showed strong disease suppression, their inconsistent performance on other parameters suggests that excessive dosage may impose physiological stress. Survivability was highest in 4 ml/L (5th–7th day) (97.50%), but the 2 ml/L (2nd & 4th day) treatment also maintained high survivability (95.20%) along with superior performance in other traits. This indicates that moderate concentration ensures a balance between immunity enhancement and metabolic stability.

Figure 2. Illustrates the Cocoon Parameters of Silkworm B.mori

Cocoon Characteristics

Cocoon characteristics showed marked improvement with Psoralea treatments, highlighting the treatments' role in enhancing silk production efficiency. The 2 ml/L (2nd & 4th day) treatment recorded the highest cocoon weight (12.20 g), pupal weight (8.80 g), and shell weight (2.60 g), indicating efficient conversion of ingested nutrients into silk proteins. This suggests enhanced silk gland activity and fibroin synthesis, which are critical determinants of cocoon quality (Elangovan et al., 2017). Although 4 ml/L (5th–7th day) exhibited the lowest percentage of defective cocoons (1.20%), indicating strong protective effects, its performance in cocoon weight and shell traits was slightly lower than that of the optimal treatment. In contrast, 2 ml/L (on the 2nd & 4th days) maintained balanced performance, with low defective cocoon rates (3.30%) and superior economic traits, making it more suitable for practical application. Shell ratio did not vary significantly among treatments, suggesting that the increase in shell weight was proportional to cocoon weight. This indicates that the treatments enhanced absolute silk yield without altering the structural composition of the cocoon. Similar findings have been reported in studies involving botanical supplementation (Narmadha & Sivaprasad, 2018). The improved cocoon traits can be attributed to improved nutrient assimilation and enhanced physiological processes induced by plant-derived bioactive compounds, thereby supporting silk protein synthesis and energy metabolism.

Table 2. Reeling Traits of B.mori under Different Treatments

Reeling Characters

Reeling traits further confirmed the positive impact of P. corylifolia extract on silk production. The 2 ml/L (2nd & 4th day) treatment recorded the highest filament length (1205.60 m) and filament weight (0.295 g), indicating enhanced silk secretion and improved silk gland function. This improvement is consistent with reports that plant extracts can stimulate fibroin synthesis and silk gland activity (Fouad & Ahmed, 2025). Although 4 ml/L (2nd & 4th day) also showed high filament length (1142.60 m), its variability across other parameters suggests that higher concentrations may not consistently support optimal silk production. Denier values across treatments remained within acceptable limits, indicating uniform filament thickness and good silk quality. The 2 ml/L treatment maintained an optimal denier (2.20), ensuring a desirable balance between fineness and strength of silk filament. The raw silk percentage was also improved in the treated groups, reflecting higher silk recovery efficiency. This indicates that treated cocoons yielded more usable silk during reeling, which is a critical economic parameter in sericulture (Rafiq et al., 2020).

The present study clearly demonstrates that the application of P. corylifolia extract has a significant positive influence on the growth, cocoon traits, and reeling performance of B. mori. The treatments improved larval health by reducing disease incidence and enhancing survival, while also improving cocoon and silk production parameters. Among all treatments, 2 ml/L extract applied on the 2nd and 4th day of the fifth instar emerged as the most effective and consistent treatment, showing superior performance in larval weight, cocoon weight, shell weight, filament length, and overall rearing efficiency. This treatment maintained an appropriate balance among growth enhancement, silk quality, and disease control. Although higher-concentration (4 ml/L) treatments showed improvements in certain individual traits, such as reduced disease incidence and fewer defective cocoons, their performance was not consistent across all parameters. This indicates that excessive concentration may lead to variability in physiological response. Overall, the study confirms that moderate concentration with early-stage application is more effective than higher doses, ensuring stable and balanced improvement in all economic traits. The findings suggest that P. corylifolia extract can be used as a promising eco-friendly biostimulant in sericulture to enhance productivity and silk quality. Further research focusing on large-scale validation, formulation standardization, and field-level application is recommended to facilitate its practical adoption in commercial sericulture.

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