It's not just aphids that get nervous: The effects of predator odor cues on aphid parasitism

Predator–prey interactions play a crucial role in shaping animal communities, population dynamics, and ecosystem functions. While predators are traditionally considered for their consumptive impact on prey populations, they also induce changes in prey behavior and physiology through non-consumptive effects (NCEs) or predation-risk effects. Insects often rely on olfactory cues for communication, and recent research indicates that these cues can also signal predation risk. Our study investigates the non-consumptive effects of natural enemies from two feeding guilds, lady beetles and parasitic wasps, on the behavior and performance of green peach aphids (Myzus persicae). We explore the role of olfactory cues in detecting predation risk using a system composed of multicolored Asian lady beetles (Harmonia axyridis), the aphid parasitoid Aphidius colemani, and collard plants (Brassica oleracea). Prior research has shown that H. axyridis odor cues can alter aphid host-plant selection, feeding behavior, and population dynamics. Additionally, parasitic wasps and other lady beetles, which are potential victims of intraguild predation, may also respond to predator chemical cues. Our greenhouse experiments assessed how lady beetle odor cues influence parasitism in aphid populations. Our results show that aphid suppression was enhanced in treatments where lady beetle presence or odor cues were introduced alongside A. colemani parasitoids. Parasitism rates, however, were similar across all treatments. Meanwhile, an initial plant-choice Y-tube assay indicated that A. colemani prefers plants without H. axyridis odor cues. Understanding how predation-risk cues affect interactions among natural enemies provides valuable insight for integrated pest management strategies.