The use of systemic insecticide affects parasitoids differently within the same feeding guild

Toxoneuron nigriceps and Campoletis sonorensis are endoparasitoids of the tobacco budworm Heliothis virescens.  These two species are valuable biological control tools in controlling tobacco budworm in Southeastern US tobacco production systems.  Field and greenhouse trials conducted from 2011-2014 compared parasitism rates and adult lifespan of these parasitoids on budworms fed with and without imidicloprid treated tobacco plant tissue.  Residues of imidacloprid and its metabolites were detectable in the bodies of budworm larvae that fed on treated plants. The two parasitoid species in our study did not have similar responses to budworms with detectable levels of imidicloprid and/or its metabolites.  T. nigriceps had a reduction in succussful parasitism rates and adult lifespan.  However, C. sonorensis did not have reduced parasitism rates or effects on adult lifespan.  These findings imply that there are ecological effects of imidicloprid use on a tritrophic level and that insecticide use may selectively affect natural enemies with similar feeding niches.