Assessing the impacts of vertical forest structure on a common insect pest

Insect herbivores are integral components of most ecological food webs. However, some insect herbivores can have devastating impacts on agriculture and plant community conservation. Fall webworm (Hyphantria cunea; hereafter FWW) is a widespread moth native to North America whose caterpillars consume over 400 plant species, including many important tree species and crops, leading to its status as a pest in parts of the United States and as an invasive species in Europe and Asia. In habit, FWW caterpillars typically build webs of 200-300 individuals in the canopies of deciduous trees on forest edges, indicating that vertical forest structure could potentially be a powerful predictor of FWW host utilization. We hypothesize that differences in forest structural characteristics such as canopy size, tree height as a proxy for age, and foliage density will predict changes in FWW presence regardless of geographical location or composition of host plant community. To test this hypothesis, we are currently exploring the effects of forest structural drivers on host plant selection across a large geographical range of FWW. In our experimental design, we perform transects along forest edges within which we record a suite of structural characteristics for trees that are both used and unused by FWW. With our results, we will identify habitat structures that are likely to experience FWW presence so that farmers and conservationists in at-risk areas can take actions aimed at protecting vulnerable plants and their habitats.