Olfactory responses of the vine weevil, Otiorhynchus sulcatus, to tree odours

A Y-tube olfactometer and a still-air olfactometer were developed to determine the attractiveness of several host plants for the vine weevil (Otiorhynchus sulcatus (F.); Coleoptera: Curculionidae). Odours of weevil-damaged yew (Taxus baccata) and spindle trees (Euonymus fortunei) are attractive to the vine weevil, but Rhododendron and strawberry (Fragaria x ananassa) are not. Undamaged Euonymus is attractive to the weevils in springtime but not in late summer. When clean air or undamaged Euonymus is the alternative, weevils strongly prefer weevil-damaged Euonymus foliage, and this preference is retained throughout the year. Hence, plant damage plays a role in attraction of the vine weevil. In contrast to the permanent attractiveness of weevil-damaged Euonymus, mechanically damaged plants gradually lose the attractiveness that they have early in the growing season. This suggests that emission of volatiles, produced by the plants in response to weevil damage, is important for attraction of the weevils because the weevils may use these plant odours to find suitable food plants throughout the season. Apart from weevil-damage-related plant volatiles, green leaf volatiles must also play a significant role, as indicated by the fact that weevils prefer: early season, undamaged Euonymus over clean air; early season, mechanically damaged Euonymus over undamaged Euonymus; and, throughout the season, had no preference when mechanically damaged Euonymus is tested against weevil-damaged Euonymus. Thus, monitoring traps may be developed by the use of green leaf volatiles and/or herbivore-induced volatiles, as attractants.