Demographic Responses of Insect Pest Populations to Climate Variability: A Regional Study of Jharkhand

Abstract

Climate change has emerged as one of the most critical drivers reshaping the population dynamics and demographic profiles of insect pest communities worldwide. Jharkhand — a state nestled in the tribal heartland of eastern India — presents a compelling case study, where shifting monsoon patterns, rising mean temperatures, and increasingly erratic rainfall regimes are quietly rewriting the ecology of agricultural pest species. This study investigates the age-specific life table parameters, intrinsic rate of natural increase (rm), net reproductive rate (R₀), doubling time (DT), and finite rate of increase (λ) of four economically significant insect pest species: the rice leaf folder (Cnaphalocrocis medinalis), the stem borer (Scirpophaga incertulas), the fall armyworm (Spodoptera frugiperda), and the brown planthopper (Nilaparvata lugens), under three distinct thermal regimes mirroring observed and projected climate scenarios in Jharkhand. Laboratory bioassays conducted at 25°C, 30°C, and 35°C over two agricultural seasons (kharif 2023 and rabi 2023–24) revealed significant temperature-dependent modulation of all demographic parameters. The rm values increased substantially from 25°C to 30°C for all species, with the most dramatic response noted in N. lugens (rm = 0.187 d⁻¹ at 30°C vs. 0.143 d⁻¹ at 25°C), indicating accelerated population build-up under projected warming. Field validation conducted across six agro-ecological zones of Jharkhand corroborated these laboratory findings, with pest pressure indices correlating positively with deviation from historical mean temperatures (r = 0.78, p < 0.01). These findings underscore the urgent need for climate-responsive integrated pest management (IPM) strategies and predictive pest forecasting systems tailored to the unique agro-climatic context of Jharkhand.