Moayeri, Hamid R. S.2; Rasekh, Arash3; Enkegaard, Annie4
1 Department of Agroecology - Entomology and Plant Pathology, Department of Agroecology, Science and Technology, Aarhus University2 Department of Plant Protection, Zanjan University3 Department of Plant Protection, Shahid Chamran University of Ahvaz4 Department of Agroecology - Entomology and Plant Pathology, Department of Agroecology, Science and Technology, Aarhus University
Insects have evolved amazing methods of defense to ward off enemies. Many aphids release cornicle secretions when attacked by predators and parasitoids. These secretions contain an alarm pheromone that alerts other colony members of danger, thereby providing indirect fitness benefits to the releaser. In addition, contact with cornicle secretions could also threaten an attacker and could provide direct fitness to the releaser. However, cornicle secretions may also be recruited as a kairomonal cue by aphid natural enemies. In this study, we investigated the effect of the cornicle droplet volatiles of the cabbage aphid, Brevicoryne brassicae (L.), on the host-searching behavior of naïve and experienced female Diaeretiella rapae (M' Intosh) parasitoids in olfactometer studies. In addition, we evaluated the role of B. brassicae cornicle droplets on the oviposition preference of the parasitoid in a two-choice bioassay. Naïve females did not exhibit any preference between volatiles from aphids secreting cornicle droplets over non-secreting aphids, while experienced parasitoids exploited the secretions in their host location. Experienced females were also able to choose volatiles from both secreting and non-secreting aphids over clean air, while this ability was not observed in naïve females. Although secretion of cornicle droplets did not influence the percentage of first attack in either naïve or experienced females, the success of attack (i.e. resulting in a larva) was significantly different between secreting and non-secreting aphids in the case of experienced parasitoids.