Hidden host mortality from an introduced parasitoid: Conventional and molecular evaluation of non-target risk

Classical biological control (CBC), i.e., the release of a natural enemy from the pest’s native range, has long been recognized as a viable approach to controlling invasive pests. CBC, because it now involves rigorous safety testing before implementation, is considered specific to a given pest and does not come with the environmental risks often associated with broad-spectrum chemical pesticides. However, accidentally introduced exotic natural enemies have not undergone screening to ensure safety, and thus may pose environmental risks, specifically to native species that are not the targets of the biological control programs. Some effects of an exotic natural enemy, such as consumption or reproduction, can be measured more readily than others. Our research points out that some of these ‘hidden effects’ can be quite important and merit our attention. We use molecular tools and modeling to help understand the hidden effects both for the target and non-target species. Our model system was an invasive fruit and vegetable pest from Asia, the brown marmorated stink bug (BMSB), Halyomorpha halys, and an exotic parasitoid, Trissolcus japonicus. T. japonicus has become established in North America and could help limit outbreaks of this pest. Unfortunately, it also kills non-target stink bugs with varying degrees of reproductive success, which may have both direct and indirect ecological effects on H. halys and non-target stink bug species.