Bringing chemical ecology into biological control: How do parasitoids find their hosts?

The process in which egg parasitoids search for and locate their hosts is not simply a remarkable feat of evolution; it is an invaluable component of biological control research that bolsters our understanding of a potential agent’s ecological host range. By exploiting a range of semiochemicals in their environment, egg parasitoids “eavesdrop” on their host’s location from long and short distances. Semiochemicals such as plant volatiles and host species’ pheromones provide parasitoids a general direction towards their host’s general habitat, while substrate-bound semiochemicals like host species footprints and host egg adhesive compounds relay more specific information on a host’s exact location and overall suitability. With these parasitoid ecology concepts in mind, Kim Hoelmer led research efforts bringing chemical ecology into classical biological control -- including refining the host range evaluation of the samurai wasp, Trissolcus japonicusHalyomorpha halys. Laboratory observations of T. japonicus exposed to H. halys and native stink bug contact kairomones on leaf substrates revealed stronger behavioral responses to cues from the wasp’s coevolved host species. Additional work suggests that parental host species may influence T. japonicus host foraging behavior, but has little effect on overall host preference and parasitism success between H. halys and suitable native stink bug species. Here we present the various studies that broaden the scope of T. japonicus host range testing through the integration chemical ecology into host range and other behavioral research in biological control.