2‑Phenylethanol and o‑Cresol Repel the Tomato Leaf Miner Phthorimaea absoluta and Attract the Parasitoid Trichogramma chilonis

Semiochemicals are biologically active compounds that modulate insect behaviors. Here, we applied a reverse chemical ecology approach to identify 2-phenylethanol and o-cresol as behavior-modulating compounds for Phthorimaea absoluta and its egg parasitoid Trichogramma chilonis. First, we identified that PabsOR27 is an odorant receptor (OR) that is highly expressed in the antennae. We then deorphanized PabsOR27 as a receptor narrowly tuned to 2-phenylethanol and o-cresol through ectopic expression in Drosophila olfactory receptor neurons and single-sensillum recordings. Furthermore, molecular docking and mutagenesis revealed Asparagine-199 as a critical amino acid residue that forms a hydrogen bond with 2-phenylethanol. Moreover, behavioral tests confirmed that both compounds act as repellents to P. absoluta, significantly reducing oviposition on treated tomato plants. Conversely, both compounds attract T. chilonis, enhancing its parasitism against P. absoluta eggs. Collectively, the dual roles of 2-phenylethanol and o-cresol position them as promising candidates for developing “push–pull” strategies for integrated pest management.