Cornmeal-based artificial diet improves development and reduces rearing costs of Spodoptera litura

The tobacco cutworm, <i>Spodoptera litura</i> (Fabricius) (Lepidoptera: Noctuidae), is a major defoliating pest in East and South Asia and serves as an alternative host for the mass propagation of the parasitoid <i>Telenomus remus</i>. Therefore, optimizing the rearing cost of <i>S. litura</i> is critical for large-scale production to enhance efficiency and reduce costs. We evaluated 18 artificial diet formulations derived from a standard diet by incorporating corn flour and adjusting the ingredient ratios. The diets were grouped into high-, medium-, and low-cost categories, and their biological performance was assessed under controlled laboratory conditions (26 ± 1 °C, 70 ± 5% RH, and a16:8 h L:D photoperiod). Among the tested diets, formulation 15 produced the best results, yielding shorter larval (19.52 d) and pupal durations (10.46 d), higher pupal mass (500 mg), greater fecundity (2,658 eggs/female), and improved egg hatch (73.77%) compared with the control. Population parameters, including the intrinsic (<i>r</i>) and finite (<i>λ</i>) rates of increase, were significantly improved, whereas the mean generation time (<i>T</i>) and net reproductive rate (<i>R₀</i> ) decreased. Importantly, formulation 15 lowered rearing costs by 5.9% relative to the original diet. These findings demonstrate that replacing soybean flour with corn flour as the primary protein source provides a cost-effective and biologically robust diet for <i>S. litura</i>. This optimized diet will facilitate large-scale rearing of <i>S. litura</i> and mechanized production of <i>T. remus</i>, providing a model for reducing artificial diet costs in other insect systems.