Sub-Lethal Influences of Azadirachta indica on Reproductive Parameters of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Abstract

This study evaluated the sub-lethal effects of neem-based formulations including commercial neem (0.15%), neem oil, and neem seed kernel extract (NSKE, 5%) on Spodoptera frugiperda under laboratory conditions. Toxicity bioassays were carried out on second instar larvae using the standard leaf-disc dip method and toxicity levels (LC₃₀ and LC₅₀) were determined for each formulation: commercial neem (0.000169% and 0.000288%), neem oil (0.045% and 0.238%) and NSKE (0.695% and 1.348%). Among the treatments, the commercial neem formulation exhibited the strongest influence on reproductive performance. Treated moths showed marked reductions in key reproductive attributes compared with untreated controls. Specifically, the oviposition period declined from 7.0 to 2.9 days, fecundity dropped from 429.6 to 141.0 eggs, and average egg size decreased from 2.280 mm³ to 1.718 mm³. Likewise, reproductive effort was substantially reduced from 979.20 to 246.15, accompanied by lower egg hatchability (64.94% vs. 92.82%) and larval survival (37.64% vs. 82.39%). These findings highlight the potential of neem formulations, especially commercial neem, in suppressing the reproductive success and survival of S. frugiperda. Their suitability as eco-friendly and sustainable components of integrated pest management make them valuable tools for maize cultivation.