Treesearch

Sudden oak death, caused by Phytophthora ramorum, was identified in late July 2001 in forest stands in Curry County on the southwest Oregon coast where it was killing tanoak (Lithocarpus densiflorus) and infecting Pacific rhododendron (Rhododendron macrophyllum) and evergreen huckleberry (Vaccinium ovatum). Affected stands occurred on industrial forest land, non-industrial forest land, and federal forest land. Treatments to eradicate the pathogen from affected sites were started in the fall of 2001 and consisted at that time of cutting, piling, and burning all infected host vegetation and...

Phytophthora ramorum is infecting plants in Oregon forests and nurseries. In this study, we analyzed the population structure of the P. ramorum in Oregon from 2001 to 2004 using microsatellites. The P. ramorum population in Oregon is characterized by low genetic diversity, significant genetic differences between nursery and forest populations, and no evidence of sexual recombination. The forest population is dominated by a single multilocus genotype in all four years, indicating the persistence of pathogen inoculum. In nurseries, identical genotypes were not recovered during both sampling...

As the emergence of invasive pathogens and their impacts on ecological communities increases, so has the interest in understanding how landscape pattern (in other words the configuration and composition of suitable habitat) affects their establishment and spread. Plant pathogen invasions are inherently spatial, but few studies have demonstrated the role of landscape pattern on disease dynamics. In this study, we investigated two hypotheses: Does the spatial pattern of host habitat predict Phytophthora ramorum disease severity, and is this relationship scale-dependent?

The number of emerging infectious diseases is thought to be increasing worldwide - many of which are caused by non-native, invasive plant pathogens I n forest ecosystems. As new diseases continue to emerge, the ability to predict disease outbreaks is critical for effective management and prevention of epidemics, especially in complex spatially heterogeneous landscapes. Mathematical modeling of susceptible-infectious transitions in plant epidemics often incorporate spatial dynamics, but are rarely applied to real-world landscape data using geographic information systems (GIS). In spite of...

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 California woodlands varies greatly among localities, and some of this variation might be explained by local variation in tree species composition and forest structure. The degree to which patterns of...

Pathogenicity of seven Phytophthora species was assessed by inoculation of stem and foliar tissues of oak species (Quercus spp.) native to the eastern United States. Phytophthora cambivora, P. cinnamomi, P. citricola, P. europaea, P. quercina ?like?, P. sp1 and P. sp2 were inoculated into stems of 1-year-old greenhouse seedlings and 2-year-old oaks grown under field conditions. Stem inoculations were conducted for 2-month periods in June and September (summer inoculation) and in October-December (fall inoculation). Stem inoculation was conducted by inserting an agar plug containing...

This paper reports on the first 2 years of data collected to study the ecology of Phytophthora ramorum in Ireland. Since spring 2005, sampling has been carried out for the presence of the pathogen in soil and watercourses from 11 susceptible forest sites in Ireland, using a rapid DNA method in conjunction with morphological identification methods. Each site was sampled twice a year, collecting foliage and using rhododendron leaves as baits for water and soil samples. In June 2005, the pathogen was positively identified as the cause of Rhododendron ponticum twig and leaf blight in Killarney...

Two new Phytophthora pathogens, Phytophthora kernoviae and P. ramorum, have recently established in parts of the U.K. They are most prevalent in the south west of England where they cause intense episodes of foliar blight and dieback on both ornamental and naturalised rhododendron such as Rhododendron ponticum, but both also cause lethal stem cankers on a range of broadleaved trees. Patterns of disease spread suggest hat both pathogens could be spread over longer distances by vertebrate movement. People and animals frequently walk through these contaminated areas and may pick up infested...

Foliar infections in California bay (Umbellularia californica) are the most important known source of inoculum contributing to Phytophthora ramorum canker in coast live oak (Quercus agrifolia). This research addressed the question whether there is a ?safe? distance between California bay and coast live oak beyond which the risk of disease is acceptably low. We quantitatively evaluated bay cover and other factors in the neighborhoods around 247 coast live oaks in long term research plots in mixed hardwood forests where P. ramorum canker has been prevalent since 2000. Both the risk and...

Sudden oak death, caused by Phytophthora ramorum (Werres, de Cock & Man in?t Veld), has killed thousands of oaks (Quercus spp.) in coastal California forests since the mid-1990s. Bark and ambrosia beetles that normally colonize dead or severely weakened trees selectively tunnel into the bleeding cankers that are the first visible symptoms to appear on infected coast live oaks, Q. agrifolia (Nee). The role of these beetles is of interest because once beetles attacked infected trees, median survival was found to decline, from seven to less than three years (McPherson and others 2005). Beetle...