Effects of belowground herbivory on predator and parasitoid foraging aboveground

Herbivores feeding on spatially separated plant parts above- and belowground can influence each other’s preference and performance through plant-mediated effects, with the most common mechanisms being plant chemical defense or nutritional changes. These changes can include quantitative and qualitative changes in plant volatiles which are used by many natural enemies to locate prey. While changes in plant volatiles due to multiple pest herbivory can alter parasitoid preference and performance, the effect on non-parasitoid predators has not been evaluated, and may have a less significant impact on foraging of natural enemies with a wider host range. Additionally, nutritional differences in prey feeding on plants with belowground herbivory may affect predator foraging through changes in handling time or behavior; parasitoid outcomes will likely track with herbivore host performance since offspring develop inside the host. To determine the effects of belowground herbivory on foraging and performance of predators and parasitoids, we used a set of choice and non-choice bioassays with corn (Zea mays) challenged aboveground by corn aphid (Rhopalosiphum maidis), or simultaneously aboveground by corn aphid and belowground by Western corn rootworm (Diabrotica virgifera virgifera). Plants were then exposed to either the convergent lady beetle (Hippodamia convergens) or an aphid parasitoid (Aphidius colemani). We paired these bioassays with an analysis of plant volatiles and plant and insect nutritional assays to determine the mechanisms governing biocontrol of aboveground herbivores in multiple pest systems. Our results provide a broader understanding of how natural enemies perform in multiple pest systems, helping us design better IPM approaches.