The Willamette Valley's Oregon white oaks have recently come under the threat of the newly invasive ambrosia beetle, Mediterranean oak borer. Researchers are studying Mediterranean oak borer to understand how this beetle behaves in Oregon and determine the level of threat posed to Oregon white oaks. One important aspect of this research is studying factors involved in host choice: why do the beetles seem to be attracted to some oaks but not others? Observationally, it seems as though oaks that already have some level of root disease, root disturbance, or stem decay are preferred by Mediterranean oak borer. This project seeks to determine if pre-existing root disease is a factor in Mediterranean oak borer host choice. Additionally, as root disease in Oregon white oaks has been only minimally studied, this project describe the incidence of root disease found in the Willamette Valley, and identify the fungal species involved.