Host egg-associated compounds elicit behavioral responses in the egg parasitoid Telenomus remus Nixon (Hymenoptera: Scelionidae)

The egg parasitoid Telenomus remus Nixon (Hymenoptera: Scelionidae) is a promising biological control agent against lepidopteran pests. Its efficacy depends on its ability to locate and recognize host eggs, however, the egg surface chemical cues underlying host recognition by T. remus remain poorly understood. In the present study, the behavioral responses of T. remus to egg-associated compounds from three host species, Corcyra cephalonica , Spodoptera litura , and S. frugiperda using a Y-tube olfactometer were examined. GC-MS profiling revealed distinct egg-surface chemical profiles among the three host species. Behavioral assays with synthetic compounds identified seven compounds that elicited significant responses in T. remus , including 1,3-di-tert-butylbenzene, toluene, oleic acid, hentriacontane, pentacosane, cyclohexanone, and tetradeca-1,13-diene. Genome-wide searches identified 14 candidate odorant-binding protein genes ( TremOBPs ) and 44 candidate odorant receptor genes ( TremORs ), which were distributed across multiple hymenopteran OBP and OR clades. Molecular docking further predicted relatively low docking scores for 1,3-di-tert-butylbenzene with several selected TremOBPs and TremORs. These results indicated that the host egg-associated compounds elicit distinct behavioral responses in T. remus . The behaviorally active compounds identified in this study provide candidate semiochemicals for future evaluation in parasitoid host-location enhancement and biological control applications, while the candidate OBPs and ORs provide molecular targets for subsequent functional validation.