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Previously, we demonstrated that wood chips, essential oil, and four individual compounds from Alaska yellow-cedar (Chamaecyparis nootkatensis [D. Don] Spach) heartwood strongly inhibit the germination f Phytophthora ramorum (Werres, de Cock, Man int Veld) zoospores or sporangia, and reduce hyphal growth in culture (Manter and others 2006). Essential oils from heartwood of incense cedar (Calocedrus decurrens [Torr.] Florin), western red cedar (Thuja plicata Donn ex D. Don), Port-Orford-cedar (Chamaecyparis lawsoniana [A. Murr.] Parl.), and western juniper (Juniperus occidentalis Hook.)...

In November 2002, Phytophthora ramorum was detected for the first time in Norway. It was isolated from Rhododendron catawbiense imported earlier the same year. After the first detection, the Norwegian Food Safety Authority has carried out surveys from 2003 to 2006. The surveys were first directed to nurseries and garden centres. Most of the positive findings were on Rhododendron spp., but one sample of Pieris japonica, one of Kalmia sp., one of Syringa sp. and one of Viburnum sp. were also positive. In 2005 and 2006, P. ramorum was isolated from well-established viburnum and rhododendron...

To date, resistance to Phytophthora ramorum in its most susceptible hosts has most commonly been quantified by lesion growth, after wounding or non-wounding inoculations via mycelia or high concentrations of zoospores. However, even highly susceptible hosts may not always become infected when they are exposed to a pathogen under ecologically realistic conditions. Therefore, resistance quantified by lesion growth may obscure an important pathway for pathogen resistance: the initial infection process. Disease resistance in plants may be characterized as either the host's ability to prevent...

Phytophthora spp. occur widely in forest and other natural ecosystems. Because these straminipiles are well adapted to aquatic environments, monitoring strategically selected streams may reflect occurrence and distribution of Phytophthora spp. over the relatively large area drained by these streams. The mountain region of western North Carolina, in the southern Appalachian Mountains, was designated as a high risk area for sudden oak death, caused by P. ramorum, based on the occurrence of numerous native host plants, a relatively mild climate, and the prevalence of nursery businesses in...

A number of molecular diagnostic procedures for detection of Phytophthora ramorum have been reported in the literature. In an effort to evaluate the specificity of 10 of these techniques a standardized DNA library for 317 isolates was assembled that included 60 described species as well as 22 taxonomically unclassified isolates. These were sent blind at a concentration of ca. 10 ng/μl (a concentration greater than would be encountered in field samples, but was used in an effort to fully evaluate specificity) to collaborators to evaluate the various diagnostic procedures. In general the...

Phytophthora ramorum, causal agent of sudden oak death, is well established over approximately 450 km of native forest along the California coast. In the course of research on this invasive exotic pathogen, two other putatively exotic aerial Phytophthora species, P. nemorosa and P. pseudosyringae, were discovered (Ivors and others 2004, Linzer and others 2006). Little is known about the ecology and biology of these other species and how they interact with P. ramorum. Preliminary research has found that P. nemorosa and P. pseudosyringae have similar host and geographic ranges and cause...

Methods for detecting Phytophthora ramorum and other Phytophthora species with rhododendron leaf baits were pilot tested in high-risk watersheds in 11 states for the purpose of recommending a national survey protocol. Ninety streams, including 14 draining P. ramorum.-endemic areas, yielded 587 baiting chances. Molecular diagnostic assays detected the pathogen in all known P. ramorum-endemic streams at least once in five baiting periods, and in nearly 50 percent of all bait leaf sets. Isolation using selective media detected the pathogen in all but one known positive stream in California...

Over the past years, ramorum blight, caused by Phytophthora ramorum, has reoccurred at specific nurseries. In many cases, the re-emergence of the disease could not be traced to a second introduction. Since it is known that P. ramorum propagules can survive for over a year in soil, it is not unreasonable to hypothesize re-emergence of the disease may be attributed to inoculum surviving in soil beds. Although the United States Department of Agriculture- Animal and Plant Health Inspection Service (USDA-APHIS) Confirmed Nursery Protocol recommends soil beds be treated with heat, chloropicrin,...

In a two year study, the spread of Phytophthora ramorum with contaminated irrigation water and the survival of the pathogen in water reservoirs were studied (Werres and others 2007). In addition at the end of each experimental period root ball samples from asymptomatic plants were taken to look for contamination with P. ramorum. For the study, an open air simulation system with nine separate container stands was used. The surplus water from each container stand ran back to a separate water basin. From the water basins, the water was taken for overhead irrigation of the plants on the...

Although Rhododendron is the most important host of Phytophthora ramorum. in Europe, there is little scientific information about the susceptibility levels of different Rhododendron species and cultivars. Increasing this knowledge would help nurseries in the management of the disease and could be used by plant protection services to target their inspections. In this study a total of 80 Rhododendron species and hybrids were screened for their susceptibility to P. ramorum using two detached leaf inoculation assays. Due to the variability in susceptibility for a given cultivar within and...