Optimization of Production Process and Evaluation of Nomuraea rileyi N6 Biopesticide Efficacy against Pieris rapae and Impact on Cabbage Quality

The entomopathogenic fungus Nomuraea rileyi is a promising biocontrol agent against lepidopteran pests, offering a sustainable alternative to synthetic insecticides. This study aimed to optimize the production process and evaluate the insecticidal efficacy of a biopesticide derived from the indigenous Nomuraea rileyi (Farlow) Samson strain N6 against the cabbage white butterfly (Pieris rapae). The effects of environmental factors on fungal growth were initially evaluated. Subsequently, solid-state fermentation (using rice and soybean flour) and different formulations (oil-based and hydrogel) were compared for cell density and viability. The biological efficacy was then tested on Pieris rapae larvae under laboratory and field conditions, followed by an economic analysis. Results indicated that Nomuraea rileyi strain N6 grows optimally at temperatures between 20–30°C and a neutral pH of 7.0–7.5. Solid-state fermentation and the oil-based formulation yielded superior cell density, while notably enhancing spore protection and adhesion. This preparation demonstrated high biological efficacy, with cumulative larval mortality of 95.2% in the laboratory at a dosage of 5 x 6.4 x 109 spores/g, and 89.1% in field trials at 10 x 6.4 x 109 spores/g. Furthermore, economic analysis revealed that using this biopesticide increased profits by 13.6% compared to conventional pesticides. Consequently, an optimized household-scale production process is proposed to effectively support sustainable local agriculture.