The efficacy, mode of action, and protective ability of neem (Azadirachta indica A. Juss.) in controlling grain coleopteran pests: A scoping review

ABSTRACT

Post-harvest losses in stored grains caused by Coleopteran pests pose a significant threat to global food security. While synthetic insecticides are effective, their extensive use has accelerated resistance development, creating an urgent need for sustainable bio-rational alternatives. Although neem (Azadirachta indica) is a widely recognized botanical insecticide, a comprehensive synthesis focusing on its specific modes of action and recent formulation advancements is lacking. This scoping review addresses this gap by systematically evaluating neem's efficacy and protective ability against stored-grain pests. Following Synthesis Without Meta-Analysis (SWiM) guidelines, we searched Google Scholar for literature published between 2000 and 2025. From 981 initial records, a multi-stage screening process selected 66 peer-reviewed studies for synthesis. The review highlights neem's multifaceted activity across six major pest families, operating through direct toxicity, repellency, oviposition deterrence, and progeny inhibition. Crucially, the analysis reveals that efficacy is highly dependent on formulation; while crude extracts vary in stability, advanced nano-encapsulated formulations and oil-based extracts demonstrate superior persistence and bioactivity while preserving grain quality. The findings confirm neem as a potent, sustainable grain protectant, particularly when integrated into broader pest management strategies, though standardized field trials are essential to bridge the gap between laboratory success and commercial scalability.