Population dynamics of major insect pests of foxtail millet (Setaria italica L. P. Beauv.) in relation to weather parameters in eastern India

Abstract

Foxtail millet (Setaria italica L. P. Beauv.) is a vital climate-resilient crop for food security in semi-arid regions, yet its productivity is severely limited by biotic stresses. This study investigated the population dynamics of major insect pests shoot fly, grasshopper, and earhead bug and their correlation with abiotic factors. Field experiments were conducted during the Kharif seasons of 2022 and 2023 at the Agricultural Research Farm, BAU, Ranchi, Jharkhand, India, using a Randomized Block Design (RBD). Results revealed a consistent temporal pattern across both years, with pest incidence initiating around the 28th Standard Meteorological Week (SMW) and reaching peak levels during SMW 32-34 (mid-to-late August). Shoot fly emerged as the most dominant pest during the seedling stage, reaching a maximum of 3.7 larvae per 10 plants. In 2023, statistical analysis showed a significant negative correlation between shoot fly populations and maximum temperature (r = -0.663*), indicating that higher thermal regimes suppress pest density. Conversely, earhead bug populations exhibited a highly significant positive correlation with rainfall (r = 0.834**) during the reproductive stage. The biological trends suggest that moderate humidity and rainfall favor pest multiplication, while excessive heat acts as a limiting factor. These findings underscore the importance of early sowing to bypass the peak infestation window of SMW 30-35. The identified weather-pest relationships provide a data-driven foundation for developing timely Integrated Pest Management (IPM) strategies, such as the use of botanical alternatives and conservation of natural enemies, to safeguard the livelihoods of smallholder farmers in rainfed agro-ecosystems.