A central question in agroecology is how to manage herbivore pests without relying on expensive and environmentally harmful pesticides. One potential method that has shown promise is to use plant cultivars with different chemical profiles, which may be more difficult for herbivore pests to deal with physiologically or make it more difficult to locate the best host plants. However, few studies have focused on the influence of specific traits and how they influence the predator-prey interaction. We performed a series of field and laboratory experiments to determine the effect of different amounts and types of plant chemical diversity on a predator-prey interaction, and how the spatial arrangement of plant chemical diversity affects insect foraging. In the first study, we found that the type of chemical diversity was more important than the overall amount of diversity for a system of Trichoplusia ni (Lepidoptera: Noctuidae), a generalist herbivore, and Podisus maculiventris (Hemiptera: Pentatomidae), a biocontrol predator. Diversity effects tended to act more strongly through growth rather than survival, and males were more strongly affected than females. In the second study we found that chemical diversity reduced the spread of herbivory within a plot, but that the arrangement of that plant diversity independent of amount reduced total feeding and was correlated with higher predator presence. Overall, successfully using plant chemical diversity to reduce pest pressure will require using the right types and amounts of diversity in arrangements that are biolocially relevant for target herbivores and predators.
Read
