Ants’ semiochemicals deters Philaenus spumarius (Hemiptera: Aphrophoridae) activity on olive trees

The meadow spittlebug, Philaenus spumarius (Hemiptera: Aphrophoridae) (L.), is the primary vector of the bacterium Xylella fastidiosa (Xanthomonadales: Xanthomonadaceae) (Wells et al.), which causes a severe vascular disease leading to significant economic losses in olive production in southern Italy. In this study, we investigated the deterrent effect of ant scent on the behavior and activity of P. spumarius on olive twigs. Using binary choice experiments, we found that the compounds released by Crematogaster scutellaris (Hymenoptera: Formicidae) (Olivier) ants significantly reduced the time spent by spittlebugs on the olive twigs. Chemical analysis of ant cuticular composition, and of ant-scented and control olive leaves identified a mixture of specific compounds, which include octadecanal, triacontane, nepetalactol, and pelargonic acid, presumably involved in this interaction. Our findings contribute to the understanding of trait-mediated indirect interactions in agroecosystems and suggest further studies focused on behavioral bioassay-based experiments to evaluate the potential role of ants’ chemical cues in P. spumarius control to preserve olive groves.