03040nas a2200169 4500008004100000022001300041245012800054210006900182260001600251300001200267490000800279520245800287100001902745700002002764700002002784856006602804 2014 eng d a0378112700aSource or sink? The role of soil and water borne inoculum in the dispersal of Phytophthora ramorum in Oregon tanoak forests0 aSource or sink The role of soil and water borne inoculum in the  cJan-06-2014 a48 - 570 v3223 a

Management of invasive species requires confidence in the detection methods used to assess expanding distributions, as well as an understanding of the dominant modes of spread. Lacking this basic biological information, during early stages of invasion management choices are often driven by available resources and the biology of closely related species. Such has been the case for the management of the phytopathogen, Phytophthora ramorum, causal agent of sudden oak death (SOD) of oaks and tanoaks. To detect P. ramorum, The Oregon SOD eradication program has relied upon the aerial observation of dead, overstory tanoak (Notholithocarpus densiflorus), an easily infected host widely distributed throughout the range of P. ramorum in Oregon. At risk is the possibility of misrepresenting the distribution of SOD, particularly if inoculum is predominately moved in soil and water, common dispersal pathways for other Phytophthora spp. To assess this risk, we performed surveys of understory vegetation in areas with a high risk of establishment of understory infection from soil and water sources: along roadsides within heavily trafficked areas with a history of SOD, and along streams known to contain P. ramorum inoculum. Additionally, we tested the alternative hypothesis of aerial dispersal, whereby infection in the understory would be spatially correlated with overstory mortality. Consistent with prior studies into the spatial structure of P. ramorum in Oregon, we found no evidence of understory infection in close proximity to roads in the absence of overstory mortality. Similarly, P. ramorum was only isolated from understory vegetation associated with streams when within close proximity to overstory sources, and more commonly further away from stream edges than within the splash and flood line. Both disease patterns are inconsistent with a dominate soil and water mediated dispersal mechanism. Rather, we found evidence supporting our alternative hypothesis of aerial dispersal whereby recovery of P. ramorum in the understory declined with increasing distance from the only known overstory source. These results support the use of aerial detection in describing the distribution of SOD in Oregon, and give further support to dispersal of inoculum in blowing fog or rain at scales not yet described for other forest Phytophthora species.

1 aPeterson, Ebba1 aHansen, Everett1 aHulbert, Joseph uhttp://linkinghub.elsevier.com/retrieve/pii/S037811271400126101849nas a2200157 4500008004100000022001400041245005600055210005600111260001600167300002000183520136400203100001901567700002001586700001901606856006601625 2015 eng d a0031-949X00aTemporal Epidemiology of Sudden Oak Death in Oregon0 aTemporal Epidemiology of Sudden Oak Death in Oregon cFeb-04-2016 a1504141246310023 a

An effort to eradicate Phytophthora ramorum , causal agent of sudden oak death, has been underway since its discovery in Oregon forests. Using an information-theoretical approach we sought to model yearly variation in the size of newly infested areas and dispersal distance. Maximum dispersal distances were best modeled by spring and winter precipitation two years before detection, and infestation size the year prior. Infestation size was best modeled by infestation size and spring precipitation the year prior. In our interpretation, there is a two year delay between the introduction of inoculum and onset of mortality for a majority of sites. The year-long gap in between allows ample time for the production of inoculum contributing to the spread of P. ramorum. This is supported by epidemic development following changes in eradication protocols precipitated by an outbreak in 2011, attributable to a 2009 treatment delay and an uncharacteristically wet spring in 2010. Post-eradication, we have observed an increase in the total area of new outbreaks and increased frequency in dispersal distances greater than 4 km. While the eradication program has not eliminated P. ramorum from Oregon forests it has likely moderated this epidemic, emphasizing the need for prompt treatment of future invasive forest pathogens.

1 aPeterson, Ebba1 aHansen, Everett1 aKanaskie, Alan uhttp://apsjournals.apsnet.org/doi/10.1094/PHYTO-12-14-0348-FI