Olfactory Responses of Trissolcus Mitsukurii to Plants Attacked by Target and Non-target Stink Bugs Suggest Low Risk for Biological Control

In crop systems, successful management of invasive insect herbivores can be achieved through the introduction of exotic biocontrol agents, i.e. parasitoids or predators, having a coevolutionary history with the pest. To avert threats to local biodiversity, recent legislations require a risk assessment for the organism to be released. Evaluation of its ability to exploit, for host location, odours associated with target and non-target species is crucial for a better definition of its ecological host range. Using Y-tube olfactometer in quarantine laboratory, we investigated the ability of the Asiatic egg parasitoid Trissolcus mitsukurii (Hymenoptera: Scelionidae) to exploit odours associated with the global invader Halyomorpha halys (Hemiptera: Pentatomidae) and with non-target stink bugs native to Southern Europe. We demonstrated that T. mitsukurii is attracted by plants exposed to feeding and egg deposition of the coevolved H. haly s or the native Nezara viridula , while it is not attracted by physogastric females or eggs alone. Remarkably, T. mitsukurii is repelled by plants bearing eggs of the beneficial stink bug, Arma custos . Our results usefully contribute to a more thorough and nuanced assessment of the potential non-target risks in case of massive parasitoid release.