Sudden Oak Death in northern California

Abstract

Phytophthora ramorum is a pathogen that can cause Sudden Oak Death (SOD) and can lead to mortality in some tree species. Our trees of study, California bay laurel (Umbellularia californica), are not killed by infection from P. ramorum but are a major vector of the pathogen to other tree species. To better understand the spread of P. ramorum in northern California, we performed a field study to explore how SOD-infected bay laurel populations differ between San Francisco and western Sonoma County. We assessed the abundance of SOD infected bay laurel in two locations in each county, collecting from 3-5 trees at each sampling location. At each tree, we counted the number of infected bay leaves we could see in 90 seconds. Our results showed a higher number of SOD infections in bay laurels in rural areas (Sonoma County) than in urban areas (San Francisco). We hope our results will help understand the spread of SOD throughout Northern California habitats and inform the community about the effects of this pathogen that impacts the biodiversity of local plants and animals. 

Keywords:  Sudden Oak Death, disease, invasive, pathogen, California bay laurel, coast live oak, forest, vector, spore, abundance, rural, ecosystem, Nathan Rank, Sci120