Olfactory responses and sensilla morphology of Hyalesthes obsoletus Signoret (Hemiptera: Fulgoromorpha: Cixiidae)

Hyalesthes obsoletus is a palearctic planthopper, natural vector of a yellow disease (Bois noir) to grapevine. Grapevine represents only an accidental plant host for this planthopper while its whole life cycle occurs mainly on bindweed and hedge bindweed (Germany and France), nettle (Germany and Italy) and chaste tree (Israel). Behavioural, morphological and electrophysiological studies were carried out in order to deepen the knowledge on the role of volatile organic compounds in H. obsoletus host plant recognition. Bioassays were performed by using a Y-olfactometer, testing the following plant species: nettle, bindweed, hedge bindweed, chaste tree and grapevine. Results showed a significant attraction of females to nettle and of males to chaste tree; males showed also a significant “non-attractiveness” for hedge bindweed. Antennal ultrastructural studies showed the presence of at least two typologies of olfactory sensilla, at the level of the pedicel: ”plaque organs”, and trichoid sensilla. Volatile organic compounds (VOCs) from nettle and chaste tree were collected, and the extracts analysed by coupling gas-cromatography to both electroantennography (GC-EAD) and mass-spectrometry (GC-MS). The VOCs were identified, and some of them were shown to elicit significant electrophysiological responses on male and female antennae. The identification of biologically active compounds and the study of behavioural mechanisms involved in host recognition are of fundamental importance to develop a new possible strategy of monitoring and control of H. obsoletus.