Treesearch

An integrated science plan was developed to identify and refine contemporary science information needs for the Lake Tahoe basin ecosystem. The main objectives were to describe a conceptual framework for an integrated science program, and to develop research strategies addressing key uncertainties and information gaps that challenge government agencies in the theme areas of (1) air quality, (2) water quality, (3) soil conservation, (4) ecology and biodiversity, and (5) integrating the social sciences in research planning. Each strategy concludes with a presentation of near-term research...

Sudden oak death (SOD) is a disease caused by Phytophthora ramorum that is characterized by lethal trunk lesions that affect tanoak (Lithocarpus densiflorus), and a few oak species, principally coast live oak (Quercus agrifolia). It was first observed in Marin County, California, in 1994, and now has been reported to have caused extensive tree mortality in the West Coast "fog belt" area that generally extends less than 30 km inland, from Monterey County, California, in the south, to Curry County, Oregon, in the north. While the plant communities vary somewhat, it is notable that the zone...

Landscape- to regional-scale models of plant epidemics are direly needed to predict largescale impacts of disease and assess practicable options for control. While landscape heterogeneity is recognized as a major driver of disease dynamics, epidemiological models are rarely applied to realistic landscape conditions due to computational and data limitations. Here we describe a stochastic susceptible-infectious epidemic model, applied to temporally and spatially heterogeneous landscape parameters, to predict the spread of the invasive forest pathogen Phytophthora ramorum, the cause of sudden...

Phytophthora ramorum was first discovered in forests of southwestern Oregon in 2001. Despite intense eradication efforts, disease continues to spread from initially infested sites because of the late discovery of disease outbreaks and incomplete detection. Here we present two GIS predictive models of sudden oak death (SOD) establishment and spread risk that can be used to target monitoring and eradication activities in western Oregon. Model predictions were based on three primary parameters: weather and climate variability, host vegetation susceptibility and distribution, and dispersal...

Phytophthora ramorum is thought to be an introduced pathogen in North America and in Europe based on the presence of only three clonal lineages. The North American lineages (NA1 and NA2) are responsible for infections in North American forests and nurseries, while the European lineage (EU1) is responsible for infections in Europe, mostly in nurseries. There have also been a few isolated findings of the EU1 lineage in North American nurseries. P. ramorum is heterothallic, with two opposite mating types, A1 and A2. The A1 mating type was originally only found in Europe, with the exception of...

Phytophthora ramorum was first detected in a Washington nursery in 2003 and has since been positively identified in 46 nurseries, three non-nursery water sites, and three landscape sites. Thirteen nurseries have tested positive for 2 consecutive years and four nurseries have been positive for 3 consecutive years, despite the completion of the U.S. Department of Agriculture Animal and Plant Health Inspection Service (APHIS) Confirmed Nursery Protocol (CNP), which is intended to eradicate this pathogen from positive nurseries. Trace-back inspections to wholesale nurseries have failed to...

Phytophthora ramorum populations in North America and Europe are comprised of three clonal lineages based on several different genetic marker systems (Ivors and others 2006, Martin 2008). Whether these lineages are ancient or a recent artifact of introduction has been unclear. We analyzed DNA sequence variation at five nuclear loci in order to better understand the evolutionary history of the three lineages and the relationships among them (Goss and others 2009). We did not see differences among isolates within each lineage, therefore the observed genetic divergence among lineages precedes...

Landscape- to regional-scale models of plant epidemics are direly needed to predict largescale impacts of disease and assess practicable options for control. While landscape heterogeneity is recognized as a major driver of disease dynamics, epidemiological models are rarely applied to realistic landscape conditions due to computational and data limitations. Here we describe a stochastic susceptible-infectious epidemic model, applied to temporally and spatially heterogeneous landscape parameters, to predict the spread of the invasive forest pathogen Phytophthora ramorum, the cause of sudden...

Phytophthora ramorum (Werres, De Cock, Man in’t Veld), which causes “sudden oak death” in the United States and dieback and leaf necrosis in ornamental plants (mainly Rhododendron and Viburnum) in Europe, is a heterothallic species with two mating types, A1 and A2 (Werres and others 2001, Rizzo and others 2002). Molecular studies on the population of P. ramorum isolates revealed a structure composed of three clonal lineages: one lineage from Europe (EU1) and two lineages from North America (NA1 and NA2) (Elliott and others 2009). Initial pairing studies revealed geographical separation of...

Phytophthora ramorum has three populations belonging to the same species: the two North American populations (NA1 and NA2) and the European population (EU1). All three populations are genetically distinct lineages, as revealed by different molecular marker systems. P. ramorum is also heterothallic, with two opposite mating types, A1 and A2. All NA1 and NA2 isolates are of the A2 mating type. All EU1 isolates have been identified as A1, except for three A2 isolates collected in Belgium in 2002 and 2003. Since 2004, no isolates of the A2 mating type have been reported in Europe, which limits...