Comparative antennal responses of Halyomorpha halys (Hemiptera: Pentatomidae) and Nezara viridula (Hemiptera: Pentatomidae) to volatiles emitted by tomatoes at different ripening stages.

Insects rely heavily on olfactory cues to locate, evaluate, and discriminate among potential host plants. Stink bugs are emerging as globally important pests whose success is closely linked to their ability to exploit plant volatile cues during host selection. The brown marmorated stink bug, Halyomorpha halys (Stål, 1855), and the southern green stink bug, Nezara viridula (Linnaeus, 1758), are important invasive pests of crops and fruit orchards, causing serious economic losses worldwide. Tomato is one of their preferred host plants, although the 2 species differ in their preferences for fruit ripening stages. To investigate the olfactory basis of host selection, we collected headspace volatiles from tomato fruits at 3 ripening stages. We analyzed their composition by gas chromatography-mass spectroscopy, with principal component analysis revealing clear differences among stages. Antennally active components within these blends were then identified by gas chromatography-electroantennographic detection using antennae of female and male H. halys and N. viridula, and their activity was subsequently confirmed with electroantennogram recordings with synthetic standards. Several compounds, including 2-carene, α-phellandrene, 3-carene, limonene, and β-phellandrene, consistently elicited antennal responses in both species and sexes. Among these, α- and β-phellandrene elicited the strongest responses. Our results provide the first identification of tomato volatile cues detected by these stink bug species and suggest that these compounds may serve as potential olfactory signals involved in host finding.