Insect responses to synthetic herbivore induced plant volatiles in an ecological framework: evidence for context dependent attraction based on varying odor blends, crop systems, and spatial scales

Herbivore-induced plant volatiles (HIPVs) have consistently been shown to attract arthropod natural enemies both in the lab and in the field. Yet, studies have found these compounds vary widely in their ability to attract specific taxa across years, systems, and deployment methods, yet no effort has been made to disentangle these variables, all of which may explain differences in arthropod responses. Additionally, there is conflicting evidence concerning the spatial scales over which HIPVs are bioactive. Insect responses to HIPVs have been assumed to operate over fairly large areas (up to 50m from lure deployment), but recent studies demonstrate these effective distances may be as small as 1.5 meters. This research, comprised of two separate experiments, was designed to investigate conflicting reports between both independent and non-independent studies. The first experiment controlled both the time of sampling and local arthropod community to explicitly test how volatile blend complexity and crop system interactively determine the attractive (or repellent) responses of arthropods on a taxon by taxon basis. The second experiment employed real time sampling to garner a better understanding of the distances over which arthropods interact with volatiles in the field, and subsequently, how arthropod distribution is altered as a result. The results of both experiments underscored the importance of context-dependent effects in determining responses in the field. Essentially, these compounds are being inserted into a complex community of interacting organisms, and to comprehensively understand the effects of HIPVs within a system it will be necessary to utilize all the available tools of ecological research