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, primarily caused by Coleopteran pests, pose a significant threat to global food security. Conventional chemical insecticides are effective but have led to widespread resistance among major pest species, necessitating alternative solutions. Neem (Azadirachta indica), a source of botanical insecticide, has emerged as a promising eco-friendly option to control Coleopteran grain pests. This scoping review synthesizes findings from 66 peer-reviewed studies published between 2000 and 2025, evaluating effectiveness of neem and its mode of action against Coleopteran pests in stored grains, as well as its role as a grain protectant. The review highlights neem's multifaceted modes of action across six major pest families. It includes direct toxicity, repellency, oviposition deterrence, and progeny inhibition. Neem formulations consistently increased pest mortality, inhibited reproduction, and preserved grain quality, with effectiveness influenced by concentration, formulation type, and application method. While neem often performs comparably to or better than other botanicals, its efficacy varies across species and storage conditions. Advanced formulations such as nanoencapsulation and integrated approaches combining neem with environmental factors show enhanced potential. Neem represents a viable component of sustainable pest management strategies, though further optimization and field validation are needed.