Herbicide exposure alters the expression of antimicrobial peptide patterns in the mealworm beetle infected with the natural entomopathogen Beauveria bassiana. XXIst scientific meeting of the Italian Association of Developmental and Comparative Immunobiology (IADCI).

Herbicide treatments are an integral part of agricultural practice. However, repeated applications lead to soil, water, and food contamination and adverse effects on non-target organisms. In this study, a pendimethalin-based commercial formulation (PND) was tested on the beetle Tenebrio molitor Linnaeus, 1758. The effects of herbicides on interspecific relationships, such ashost-pathogen interaction are poorly studied. In the laboratory, adults were exposed to two different doses, the concentration corresponding to the contamination of the treated soil and the maximum residue level allowed by the EU in cereals. The beetles were then exposed to an inoculum with the entomopathogenic fungus Beauveria bassiana (Bb), commonly used as a bioinsecticide. Survival, sporulation of the fungus in cadavers, and expression levels of antimicrobial peptides (AMPs) Tenecin 1, 2, and 3 were examined. Although the survival rate did not change significantly between control and herbicide-exposed beetles, an alteration in the expression pattern of inducible AMPs was recorded. PND-treated beetles showed up-regulated Tenecin 1 and Tenecin 2 after inoculation with Bb. In addition, a slight increase in Bb sporulation on cadavers was recorded at the highest dose of the herbicide. Our results showed a potential alteration of the host-pathogen interactions, raising the question of bioinsecticide compatibility with synthetic pesticides and the effects of herbicides on interspecific relationships in wild species.