ABSTRACT Sources of inoculum were investigated for dominant hosts of Phytophthora ramorum in a redwood forest. Infected trunks, twigs, and/or leaves of bay laurel (Umbellularia californica), tanoak (Lithocarpus densiflorus), and redwood (Sequoia sempervirens) were tested in the laboratory for sporangia production. Sporangia occurred on all plant tissues with the highest percentage on bay laurel...

California bay laurel trees (Umbellularia californica) play a crucial role in the reproduction and survival of Phytophthora ramorum in coastal California forests by supporting sporulation during the rainy season and by providing a means for the pathogen to survive the dry, Mediterranean summer. While bay laurel is thus critical to the epidemiology of sudden oak death and other P. ramorum diseas...

Introduced plant pathogens have major ecological impacts in many parts of the world. While the spread of pathogens can be strongly mediated by the composition and structure of local host plant communities, little is known about effects of plant community structure on invasion dynamics of introduced pathogens. The progress of infection by the invasive pathogen Phytophthora ramorum in coastal Cal...

ABSTRACT During 2001 to 2003, the transmission biology of Phytophthora ramorum, the causal agent of sudden oak death, was studied in mixedevergreen forest, a common forest type in northern, coastal California. Investigation of the sources of spore production focused on coast live oak (Quercus agrifolia) and bay laurel (Umbellularia californica), dominant hosts that comprised 39.7 and 46.2% of t...

The ecophysiologic role of fog in the evergreen heath-laurel 'laurisilva' cloud forests of the Canary Islands has not been unequivocally demonstrated, although it is generally assumed that fog water is important for the survival and the distribution of this relict paleoecosystem of the North Atlantic Macaronesian archipelagos. To determine the role of fog in this ecosystem, we combined direct t...

The first wildfires in sudden oak death-impacted forests occurred in 2008 in the Big Sur region of California, creating the rare opportunity to study the interaction between an invasive forest pathogen and a historically recurring disturbance. To determine whether and how the sudden oak death pathogen, Phytophthora ramorum, survived the wildfires, we completed intensive vegetation-based surveys...

The transmission ecology of Phytophthora ramorum from bay laurel (Umbellularia californica) leaves was compared between mixed-evergreen and redwood forest types throughout winter and summer disease cycles in central, coastal California. In a preliminary multisite study, we found that abscission rates of infected leaves were higher at mixed-evergreen sites. In addition, final infection counts we...

Umbellularia californica (California bay laurel) and Laurus nobilis (Mediterranean bay laurel) leaves may be mistaken or used as a substitute on the market due to their morphological similarity. In this study, a comparison of anatomical and chemical features and biological activity of both plants is presented. L. nobilis essential oil biting deterrent and larvicidal activity were negligible. On...

Recent research has shown that Phytophthora ramorum is a major threat to California’s coast live oak (Quercus agrifolia) dominated, mixed-evergreen forests (Rizzo and Garbelotto 2003). However, the role that diseases caused by other Phytophthora species play in the ecology of these forest communities is less evident. Surveys in mixed-evergreen forests have revealed two additional Phytophthora s...

Phytophthora ramorum is an alien and invasive plant pathogen threatening forest ecosystems in Western North America, where it can cause both lethal and non-lethal diseases. While the mechanisms underlying the establishment and spread of P. ramorum have been elucidated, this is the first attempt to investigate the environmental factors driving the recovery of bay laurel, the main transmissive ho...