LAUSR

Simple Summary The leaf beetle Labidostomis lusitanica (Germar) (Coleoptera: Chrysomelidae) is a voracious defoliator beetle regarded as a threat for pistachio (Pistacia vera) crops in Spain. During late April–early June, field aggregates containing both sexes are commonly found in pistachio leaves. Males collected from these aggregates release a sex-specific compound, namely 2-isobutyl-3-methoxypyrazine, that elicits both a strong electrophysiological response and positive chemotactic behavior in males and females. Altogether, our findings suggest that 2-isobutyl-3-methoxypyrazine may act as an aggregative cue, although further field assays are required to address the true role of the compound in natural conditions. Abstract In spite of its incidence on pistachio trees, the chemical ecology of Labidostomis lusitanica (Germar) (Coleoptera: Chrysomelidae) has been neglected so far. In this work, we provide the first evidence of a biologically active male-specific compound that may be promoting field aggregation. Headspace collections through solid-phase microextraction from feral males and females reported the presence of 2-isobutyl-3-methoxypyrazine exclusively in males. Electroantennographic recordings revealed that males and females responded in a dose-dependent manner to increasing stimuli of 2-isobutyl-3-methoxypyrazine, with females overall displaying a higher response than males. In dual-choice tests, both males and females showed a significant preference for the compound in comparison to a pure air stimulus. In light of these results, the possible role of 2-isobutyl-3-methoxypyrazine as an aggregation cue in L. lusitanica is discussed.