ABSTRACT

Mulberry (Morus spp.) is the sole food source of the silkworm, Bombyx mori L., and forms the backbone of the sericulture industry, where leaf quantity and quality directly determine cocoon yield and silk productivity. Among the defoliating pests of mulberry, the leaf roller Diaphania pulverulentalis Hampson is one of the most damaging, causing leaf folding, webbing and continuous feeding on tender foliage that reduces photosynthetic efficiency and harvestable yield. The present study examined the biology, seasonal incidence, life table parameters and economic impact of D. pulverulentalis under laboratory and field conditions across three mulberry-growing localities in Tamil Nadu, India (Karapalli–Hosur, Uthiramerur–Kanchipuram and Mayiladumparai–Theni), during 2024–2026. The total life cycle was shortest in summer (25.00 ± 2.00 days) and longest during the Rabi season (39.50 ± 3.10 days). Field population ranged from 0.18 to 2.22 larvae per plant, peaking in August and November and declining sharply in summer. Population was significantly and negatively correlated with maximum and minimum temperature (r = -0.56 and -0.55, respectively; p < 0.05) and significantly and positively correlated with evening relative humidity (r = 0.52; p < 0.05), while correlations with morning relative humidity and rainfall were not statistically significant. Stage-specific life table analysis identified the pupal stage (21.43% mortality) and fifth instar (12.50%) as the principal points of population regulation, with survivorship declining from 100 individuals at the egg stage to 44 at the adult stage. Pest population was very strongly and significantly correlated with both leaf yield loss (r = 0.99, p < 0.001) and economic loss (r = 0.91, p < 0.001), and infestation exceeding the economic threshold level (ETL) resulted in disproportionately higher damage grades and monetary loss. These findings indicate that timely, ETL-based monitoring - targeting the pupal and late-larval stages identified here as the principal mortality windows - can substantially reduce both pesticide use and yield loss, supporting its adoption as a practical component of integrated pest management for sustainable mulberry cultivation in Tamil Nadu.