Impact of Predation Risk on the Behavior and Physiology of Insects in Agricultural Systems

ABSTRACTNon-consumptive effects are impacts on prey survival and performance that are related to investment in anti-predator defenses. Without considering direct consumption by predators, non-consumptive effects contribute a large portion of the net effects of predatory insects have on their prey. Because the central tenant of agricultural systems is to produce the highest profitable yield; understanding how we can harness, manipulate, and foster predator non-consumptive effects will be helpful in development of pest management techniques. While non-consumptive effects are now known to occur quite commonly, both the spatial and temporal scale of studies are limited (demonstrated in Chapter 1). It is therefore necessary to expand our work to better understand these interactions in natural systems over longer time periods. Here I examined the potential for non-consumptive effects in an important agricultural predator-prey system between a common herbivore prey (Pieris rapae) and ubiquitous predator (Harmonia axyridis) in both the laboratory (Chapter 2) and field (Chapter 3). Interestingly, even though these species overlap in spatial distribution and phenology, little to no effect of predation risk on prey behavior was found. Further, when examining their interactions in an open-field environment, no significant non-consumptive effects on Pieris rapae were found. However, manipulatively increasing predator cues in the open-field experiment did have significant impacts on a secondary insect pest (Aphidae spp). This work emphasizes the importance of examining community interactions at the field level. In addition, non-consumptive effects resulting from H. axyridis on aphids (Myzus persicae) were found to be strong, resulting from changes in both aphid behavior and physiology (Chapter 4). Overall, these studies demonstrate that predator non-consumptive effects are prey species dependent and that studies in natural settings, over larger spatial and temporal scales, will allow us to better understand these complex interactions.