Exploitation of pentatomids by native egg parasitoids in the native and introduced ranges of Halyomorpha halys: a molecular approach using sentinel egg masses

Following introduction of Halyomorpha halys in Europe and North America, a concerted effort has been made to characterize host–parasitoid interactions involving H. halys. Yet, it is unclear whether the reported low parasitism in the field is due to the rejection of H. halys by native parasitoids, or the inability of larvae to develop. To determine whether native and exotic pentatomids are equally exploited by native parasitoids in the introduced range of H. halys, sentinel stink bug (native and exotic) egg masses were exposed in different habitats and the incidence of parasitism was determined by rearing and DNA-based approaches. Parasitism estimates were always lower with rearing compared to the molecular method. Egg masses of both native and exotic host species were equally likely to be attacked under natural conditions, supporting the idea that H. halys represents an evolutionary trap for native parasitoids. Lack of parasitoid emergence from H. halys eggs is probably not due to native parasitoids rejecting this host, but rather due to the inability of larvae to complete development. The frequent parasitization of H. halys by native parasitoids highlights the possibility of interspecific interactions with natural enemies considered for introduction as part of biological control programme (e.g. Trissolcus japonicus). Oviposition in eggs of the unsuitable H. halys host by native parasitoid may also have population-level consequences for both parasitoids (e.g. reduced population size, shifts in parasitoid community composition) and pentatomids (e.g. competition with H. halys, deceased population regulation by parasitoids). These effects should be considered when developing biological control strategy for H. halys.