Exploring the landscape of fear: the role of non-lethal predator effects in manipulating Pieris rapae

Predators have been used to control insect pest populations for decades but the concept and strength of biological control relies solely on the lethal ability of high predator populations in agroecological systems. More recently studies have found insect herbivores have the ability to perceive and respond to predation threat by taking advantage of various predator cues. Prey behavioral changes that arise from this apparent threat can result in reduced damage to prey host plants as well as reduced prey population size. Even with increasing evidence that non-lethal predator effects are more robust than lethal effects, studies have yet to explore the landscape of fear concept as a pest management tactic. Our research provides insight into the non-lethal effects of lady beetle predators on a common lepidopteran pest, the imported cabbageworm (Pieris rapae). We measured host choice and oviposition of the adult butterflies in the presence of real and perceived predation threat. In greenhouse experiments we were able to manipulate perceived threat at the plant scale by using chemical and visual cues that imitate the ladybug. In field experiments done in experimental plots within the NSF Long-term Ecological Research site at Kellog Biological Station we were able to look at the impact of non-lethal predator effects on P.rapae populations at multiple landscape scales and varying landscape heterogeneity.