Abstract :
[en] Wireworms (Coleoptera: Elateridae) are major soil-dwelling pests in European agroecosystems, and their management has become increasingly challenging following restrictions on chemical insecticides. This thesis explores the potential of entomopathogenic nematode-bacteria complexes (EPN) as alternatives for wireworm control, moving beyond a purely biocidal paradigm toward a behavioral and ecosystem-based approach.
First, we investigated how wireworms select host plants and demonstrated that host choice is driven by a combination of olfactory cues and gustatory evaluation, with sugars enhancing host susceptibility and compounds such as glycoalkaloids mediating avoidance. These findings provided a basis for identifying natural plant-derived attractants suitable for behavioral manipulation. Second, we assessed the virulence of multiple EPN populations against wireworms and revealed that infection success is strongly constrained by the host’s physical barriers and by nematode morphometric traits, highlighting intrinsic limitations of this biological control agent against wireworms.
Building on these insights, we developed an attract-and-kill strategy based on the co-encapsulation of natural attractants with EPNs or their bacteria in alginate beads. Although the formulations effectively attracted wireworms, infection rates remained low, underscoring the need to rethink how biological agents are delivered in soil systems. We therefore shifted our focus beyond direct parasitism to examine the secondary metabolites produced by nematode-associated symbiotic bacteria. These metabolites disrupted wireworm behavior through volatile-mediated repellence and significantly inhibited egg hatching, revealing potent sublethal effects despite the absence of larval mortality.
Finally, adopting an ecological perspective, we demonstrated that EPN infection reprograms the chemical phenotype of insect cadavers, generating conserved volatile signatures that elicit species-specific behavioral responses and shape soil trophic interactions. Collectively, this work reveals that the nematode-bacteria complex functions not only as a biological control agent but also as a chemical engineer of soil ecosystems. By integrating behavioral ecology, chemical ecology, and applied biological control, this thesis opens new avenues for sustainable wireworm management through multifunctional strategies that exploit both lethal and sublethal effects of entomopathogenic nematodes and their bacterial symbionts.
