The very scary ladybug: Investigating how top-down stressors influence plant-insect interactions

Natural enemies are valuable partners for crop growers in managing the pest insects in agroecosystems. Typically, we value natural enemies based on their ability to consume insect herbivores and therefore remove the pest from the crop. However, the mere risk of predation can provoke changes in herbivore behavior and physiology that can influence herbivore reproductive capacity and survival. It has been shown that predation risk can reduce insect herbivore populations almost as significantly as predation itself. Despite this promise, little work has been done to harness risk effects as a potential pest management strategy, in addition to identifying the mechanisms insect herbivores use to identify predation risk. The goal of our research is to 1) identify what mechanisms insect herbivores use to determine predation risk and 2) successfully mimic those cues. We ask these questions using the herbivorous green peach aphid (Myzus persicae (Sulzer)), the predatory multi-colored Asian lady beetle (Harmonia axyridis), and collards (Brassica oleracea) as a system. Our research has demonstrated that H. axyridis odor cues reduce M. persicae reproductive capacity, deter host-plant colonization, and stifle aphid population size. Ultimately, our goal is to characterize and synthesize the odor profile of Harmonia axyridis by identifying the compounds using GC-MS, and assessing their bioactivity of the compounds using GC-EAG.  This work highlights a promising area of research that merges chemical ecology with sustainable pest management.