Electromagnetic properties of diseased oaks

Aboumrad 2019: Sudden oak death (SOD) is a blight on a number of oak and tanoak species common to coastal California and parts of southern Oregon. The disease is caused by latent infections of a water mold plant pathogen, and external symptoms, such as lower-trunk cankers dripping of thick, sticky sap, are generally not exhibited until the infection reaches an advanced stage of development, at which point the oak trees are especially susceptible to infestations by ambrosia beetles, bark beetles, and sapwood decay fungal colonies. We developed a microwave testing procedure for assessing the electromagnetic (dielectric constant, resistivity) properties of oak trunk samples, with the aim of discovering statistically-significant differences in some or all of these properties at both SOD-infected vs healthy samples. This exploratory research yields insight into the underlying physical traits of SOD symptoms and/or contribute to the continued development of non-invasive testing procedures on biological specimens.

Ancora et al 2019: Bay laurels are the primary host of P. ramorum in California. To investigate the health of bay laurels on the Fairfield Osborn Preserve, we measured shade coverage and the prevalence of flowers in two parts of the Preserve. We found flowering bay laurels only at lower elevations.