Determining Sudden Oak Death, Phytophthora ramorum, Presence on Mt. Wanda at John Muir National Historic Site (JOMU), Martinez, CA
Soumya Suresh, Oregon State University
Angelica V. Sprague, John Muir National Historic Site, National Park Service
Victoria Seher, John Muir National Historic Site, National Park Service
The fungus-like plant pathogen, Phytophthora ramorum, has been the cause of sudden oak death (SOD) in millions of oaks, primarily in coast live oak (Quercus agrifolia) and tanoak (Lithocarpus desiflorus) trees in California. It is characterized by the development of seeping cankers on the trunk of trees, foliage dieback, and eventual death of some individuals. The invasive pathogen was first reported in the mid 1990's, inadvertently spread by contaminated nursery stock. It is now distributed in Contra Costa County and several central and northern coastal California counties. Phytophthora ramorum has been confirmed in surrounding Contra Costa areas approximately 2 miles from the John Muir National Historic Site and Mt. Wanda, a popular urban park. The California bay laurel (Umbellularia californica), a host species commonly found on Mt. Wanda, tested positive for Phytophthora psedudosyringae, a species in the same family as SOD.
We will begin our exploration for the presence of P. ramorum on Mt Wanda by determining soil acidification in potential SOD host species. Increased soil acidification due to climate change and pollution, decreases the plant’s ability to take up nutrients such as nitrogen, phosphate and potassium. The decrease in pH or increase of negative ions by acid rain and bryophytes immobilizes heavy metals such as aluminum in pH lower than 4.5. The heavy metals interfere with mycorrhizal fungi and fine root growth which are directly responsible for nutrient uptake. The reduction of the uptake of these essential nutrients leaves the oaks vulnerable to attacks by pathogens such as P. ramorum. We will continue with SOD testing in Spring 2021 by collecting tissue and/or leaf samples. This project will give JOMU resource managers key information and potential recommendations on sudden oak death management on Mt. Wanda.