Impact of Weather Variables on Radish Insect Pests in the Eastern Himalayas and Organic Management Strategies

Abstract

This study analyzed the impact of weather variables on insect pest dynamics and their diversity in the radish ecosystem through field experiments conducted for two years at a locality in the eastern Himalayas. The relationship with weather variables was studied with six different dates of sowing, and diversity was assessed using standard indices. Various organic management options were also evaluated. Results revealed that temperature had a positive impact, whereas relative humidity and rainfall negatively affected the population of insect pests. The radish ecosystem harbors diverse insect species, including natural enemies, with higher species richness (4.8–5.2) and lower year-to-year variability. Organic management strategies such as neem oil, Beauveria bassiana, and Metarhizium robertsii demonstrated good efficacy against flea beetles without compromising yield, resulting in 39.76%, 39.39%, and 38.71% pest reduction over control, respectively. These biopesticides also recorded less than half to one-fourth reduction in natural predators like coccinellids compared to cypermethrin, a chemical pesticide (74%). The study suggests that, under projected climate change with higher temperatures, pest populations are assumed to increase. Considering the insect diversity of the eastern Himalayas, organic management strategies will be an adaptation strategy to conserve biodiversity while ensuring environment-friendly pest management.