The hidden costs of biocontrol: sublethal effects of entomopathogenic fungi formulation on non-target soil species

The restriction of synthetic pesticides has driven the development of sustainable pest control approaches, including formulations based on entomopathogenic fungi (EPF). While EPF show strong potential for controlling soil pests such as wireworms, their non-target effects, particularly sublethal and behavioral impacts, remain insufficiently characterized. In this study, we evaluated the ecological safety of a novel EPF-based formulation against three non-target soil species: the black garden ant (Lasius niger), the ground beetle (Pterostichus melanarius), and the earthworm (Eisenia fetida). Ant colonies were exposed for either one or 24 hours to the formulation, revealing no effect on survival or foraging dynamics. Continuous exposure of P. melanarius over 21 days did not affect survival, although behavioral monitoring indicated an increase in biting activity in the presence of the formulation, potentially linked to stress-related or exploratory responses. In E. fetida, 28-day exposure caused no significant changes in survival, reproduction, or locomotion, yet slight weight reduction and enhanced foraging behavior were observed. Overall, the results indicate that the EPF formulation is not lethal to the tested non-target organisms but can induce subtle behavioral and physiological modifications. These findings suggest that incorporating behavioral and sublethal endpoints into ecological risk assessments of biocontrol agents may improve the prediction of their long-term ecosystem effects, particularly regarding soil functioning and trophic interactions.