Herbivore-induced plant volatiles (HIPVs) from companion plant could enhance predator recruitment and biocontrol of cereal aphids

Herbivore-induced plant volatiles (HIPVs) can act as signaling molecules mediating ecological interaction.The annual plant Cnidium monnieri (L.) Cusson may support populations of natural enemies, notably serving as a bridge habitat that helps predator migration to adjacent fields for pest control.The role of HIPVs recruiting Harmonia axyridis (Pallas Coleoptera: Coccinellidae) and result in affecting the biological control of cereal aphids is partially documented.Here, we found that H. axyridis has a strong predatory capacity against Semiaphis heraclei (Takahashi Hemiptera: Aphididae), exceeding that of other ladybeetle species tested in predation assays.Behavioral assays showed that both male and female H. axyridis adults were significantly attracted to S. heraclei-infested C. monnieri, with females displaying higher sensitivity to aphid-infested plants.GC-MS analysis identified increased emissions of specific HIPVs in S. heraclei-infested plants, particularly terpenes such as β-myrcene, which was found to attract H. axyridis at moderate concentrations (200 μg/mL).Further homology modeling revealed that β-myrcene and (cis)-3-hexenyl acetate binds effectively to H. axyridis odorantbinding proteins (HaxyOBPs), with molecular docking studies identifying key residues involved in ligand interactions.These findings suggest that S. heraclei-infested C. monnieri emits HIPVs, especially β-myrcene, that enhance the attraction of H. axyridis and support natural pest regulation.This study provides insights into the mechanisms of tri-trophic interactions, offering a foundation for using functional plants in pest management strategies of crops.