Identification of compounds from the egg volatiles of Asia corn borer, Ostrinia furnacalis, that attract egg parasitoid, Trichogramma ostriniae.

BACKGROUND

The egg parasitoids, Trichogramma ostriniae (Hymenoptera: Trichogrammatidae), is an important biological control agent against the Asia corn borer, Ostrinia furnacalis, a destructive maize pest. These short-lived wasps (adult longevity of several to tens of days) have to locate their host within a limited time by exploiting reliable cues related to their hosts, for example, host egg volatiles. This study identified specific compounds in O. furnacalis egg volatiles that attract female Trichogramma ostriniae and tested the effects of these compounds and synthetic sex pheromones analogue of O. furnacalis, (Z)-12:14AC and (E)-12:14AC with a ratio of 47:53 (ZE) on parasitism of Trichogramma ostriniae on O. furnacalis eggs in a maize-plant cage.

RESULTS

The egg volatiles from O. furnacalis and Helicoverpa armigera were the most attractive to Trichogramma ostriniae among the egg volatiles of five host tested species. Among the 13 specific compounds identified in O. furnacalis egg volatiles using gas chromatography-mass spectrometry (GC-MS) analysis, Trichogramma ostriniae females preferred six compounds (oleic acid, stearic acid, dioctyl phthalate, tetracosane, palmitic acid, and 4-hydroxyphenylethanol), and were repelled by three (heptadecanoic acid, phenylacetaldehyde, and elaidic acid). Trichogramma ostriniae females showed a significant preference for 'OSDTP4' (a mixture of the six preferred compounds) at 1, 0.1, and 0.01 μg/μL, but not at 10 and 0.001 μg/μL. The females preferred ZE, at 1 and 10 μg/μL, but not at 0.001, 0.01, and 0.1 μg/μL. In the cage and field experiments, Trichogramma ostriniae displayed higher parasitism rate on O. furnacalis eggs treated with OSDTP4, ZE, or their mixture than the control. The mixture of OSDTP4 and ZE was more effective in promoting parasitism than either alone.

CONCLUSION

The present results identified six specific compounds from volatiles of O. furnacalis eggs attract to Trichogramma ostriniae females. By enhancing the attraction of Trichogramma ostriniae to O. furnacalis eggs, we can potentially improve capability of parasitoid wasps to find the target pest and increase the efficacy of Trichogramma ostriniae against O. furnacalis in biological control programs. © 2025 Society of Chemical Industry.