Carrier Formulations to Enhance Conidial Viability and Pathogenicity of Beauveria bassiana against Spodoptera frugiperda Larvae

Background: Beauveria bassiana is an entomopathogenic fungus widely utilized as a biological control agent against various insect pests, including Spodoptera frugiperda. Objectives: This study aimed to analyze the effect of oil-based formulations on the conidial viability and efficacy of B. bassiana in infecting S. frugiperda larvae. Methods: The research was conducted from May to November 2025. An in vitro study was performed to observe conidial viability across various formulations over storage periods ranging from 7 to 35 days at room temperature. Subsequently, an in vivo assay was conducted to evaluate the efficacy of the two most viable formulations against S. frugiperda larvae in comparison to a control group. The tested treatments included B. bassiana combined with sterile distilled water (control), paraffin oil, virgin coconut oil (VCO), soybean oil, and glycerol. Results: VCO formulation exhibited the highest conidial viability after 35 days of storage (69.2% germination), followed by paraffin oil (55.4%), soybean oil (47.6%), and glycerol (41.4%), while the control showed the lowest viability (25.0%). Both VCO and paraffin oil formulations achieved 100% larval mortality by the seventh day. In contrast, the control group reached only 98% mortality by the tenth day, with some larvae successfully pupating. Conclusion: These findings suggest that oil-based carriers, especially VCO, optimally enhance the stability of B. bassiana conidia during storage and increase their infectivity against S. frugiperda. Furthermore, VCO is a superior carrier due to its plant-based origin and environmental sustainability.