Integrating fungal virulence, formulation, and volatile-mediated attraction for an effective attract-and-kill strategy against Agriotes spp.

Introduction The progressive withdrawal of soil insecticides has created an urgent need for sustainable alternatives against Agriotes wireworms. Here, we evaluated an attract-and-kill strategy based on entomopathogenic fungi (EPF) designed to overcome the spatial and behavioral constraints that limit biocontrol efficacy in soil. Methods Our approach integrated in vitro virulence screening, in vivo efficacy assays using starch-enriched alginate beads in sterilized soil microcosms, dual-choice olfactometer bioassays, and volatolomic profiling by thermal desorption gas chromatography coupled with mass spectrometry. Results Ophiocordyceps sp. MUCL 58550 exhibited the highest in vitro virulence, yet its efficacy declined in soil microcosms. Volatolomic and behavioral analyses suggest that this loss of performance resulted from poor larval attraction, as its profile blend was dominated by ubiquitous alkanes and carbonyl compounds. In contrast, Metarhizium anisopliae MUCL 58549 maintained high efficacy in vivo and elicited positive chemotaxis (65% choice). This response was associated with a distinctive volatile signature enriched in sesquiterpenes (e.g., aristolochene and eremophilene). The non-pathogenic strain Trichoderma harzianum MUCL 29707 induced the strongest attraction (70% choice), consistent with a volatile profile enriched in C8 oxylipins, including 1-octen-3-ol and 3-octanone. Discussion However, its inability to infect wireworms highlights the risk of creating pest “safe havens” if attraction is not coupled with lethality. Although the causal role of individual volatile compounds remains to be validated, these results demonstrate that effective biological control relies on a “dual-action” mechanism. Specifically, the integration of volatile-mediated host recruitment with targeted pathogenicity enables formulated EPFs to function as active lethal sinks, offering a viable framework for sustainable wireworm management, pending future field validation.