Canyon live oak (Quercus chrysolepis) is susceptible to bole infection by Phytophthora ramorum.

Author , , ,
Date 2011.
Publication Phytopathology 101:S8.
Key Words
AbstractCanyon live oak (Quercus chrysolepis) was originally shown to be susceptible to leaf and twig infection by Phytophthora ramorum (cause of Sudden Oak Death, SOD). Recently, mortality of large Q. chrysolepis was observed in a SOD-affected forest along with trunk symptoms indicative of late-stage P. ramorum infection. Symptomatic trees showed spatial correlation with California bay (Umbellularia californica), the primary source of P. ramorum inoculum in oak-bay forests. However, the pathogen was not recovered from cankers sampled through 2009. To determine the susceptibility of Q. chrysolepis to P. ramorum, we inoculated 12–20 cm diameter, 120 cm long, logs of disease-free Q. chrysolepis and Q. agrifolia trees with mycelial plugs of 7 P. ramorum isolates. Inoculated logs were enclosed in plastic bags and maintained in 20°C growth chambers. At 8 weeks, 90% of the inoculations had resulted in visible cankers with a mean canker size of 57 cm2 in Q. chrysolepis and 228 cm2 in Q. agrifolia. P. ramorum was recovered from nearly all canker margins. Field inoculations were conducted on 18 Q. chrysolepis trees in July 2010. Over the next three months, only four inoculated trees showed minimal visible trunk symptoms (i.e., bleeding). In December 2010, four inoculated trees were destructively sampled. All inoculations resulted in cankers similar in size and appearance to those observed with the logs; P. ramorum was recovered from canker margins in all cases.
Full Citation Aram, K.; Swiecki, T.; Bernhardt, E.; and Rizzo, D.M. 2011. Canyon live oak (Quercus chrysolepis) is susceptible to bole infection by Phytophthora ramorum. Phytopathology 101:S8.