An Apple a Day Does not Keep the Weevils Away: Enhancing Vine Weevil Monitoring with Fruit-Based Volatiles

This study investigated the behavioural and electrophysiological responses of adult vine weevils to apple sauce volatiles under laboratory conditions, using Y-tube olfactometer bioassays and headspace analysis using gas chromatography coupled to mass spectrometry (GC-MS) and GC coupled to electroantennographic detection (GC-EAD). In Y-tube bioassays, more adults selected the olfactometer arm containing apple sauce volatiles compared to the control arm at lower doses (0.1 g, 1 g and 10 g) but not at higher dose (20 g). Thirteen compounds were identified in volatiles collected from apple sauce with the major components being furfural and sorbic acid. Consistent electrophysiological responses were recorded to (E)-2-heptenal, 1-hexanol, (Z)-3-hexenol and (E)-2-hexenol. The behavioural response of vine weevil adults to refuges baited with semiochemical lures was also tested under glasshouse conditions. In this scenario, a greater proportion of individuals were recorded in refuges baited with apple sauce compared to unbaited refuges. A similar behavioural response was also recorded when refuges were baited with a combination of apple sauce and Fortune's spindle (Euonymus fortunei (Turcz.) Hand.-Maz.; Celastrales: Celastraceae) compared to those that were unbaited or individually baited with Fortune’s spindle or apple sauce. This study indicates that apple sauce influences vine weevil behaviour and could serve as a basis for developing a novel lure for improved monitoring.