Treesearch

Once Phytophthora ramorum is introduced into a nursery on a host, its local spread and establishment is primarily dependent on sporangia and zoospore production. Nursery operators commonly use fungicides to prevent the establishment of Phytophthora –caused diseases, although current research only supports the use of fungicides for preventing infection. It is still unknown, however, what effect fungicide treatments have on sporulation, spread, and persistence of the pathogen on established infections. With this additional knowledge, fungicide treatments could be more effectively used to...

The objective of this work was to establish inoculum density relationships between Phytophthora ramorum and selected hosts based on whole plant inoculations. Knowledge of levels of initial inoculum needed to generate epidemics is needed for disease prediction and development of pest risk assessments. Sporangia of six P. ramorum isolates representing the NA1 and EU1 clonal lineages were produced by incubating 20 percent V8- juice agar plugs containing mycelium, in 1 percent soil extract for 48 hours and adjusting the suspensions to 0, 50, 100, 500, 1,000, 2,000, and 3,000 sporangia/ml....

For Phytophthora spp. that are quarantine or regulated organisms, highly specific and sensitive diagnostic tools are recommended for surveys and monitoring. Furthermore, these diagnostic techniques should give results within a short time and should be not be too expensive. The techniques currently used for routine diagnosis of Phytophthora spp. in plant tissue are mainly molecular techniques (conventional and real-time PCR) and direct isolation. They require that samples must be brought to a diagnostic lab with specific equipment. This takes time and means financial losses for the commercia...

Rhododendron maximum L. and R. catawbiense Michx. are two species that are native to the eastern United States. They can be found throughout the Appalachian Mountain range and during bloom are very important tourist attractions. Phytophthora ramorum is known to be pathogenic to both species, although no symptoms have been observed in wild habitats in the eastern United States. Endophytic fungi are known to have a symbiotic relationship with their host, including protection against pathogens. It was the purpose of this study to survey natural stands of R. maximum and R. catawbiense in the...

Phytophthora species are known as pathogens of agricultural crops or invasive pathogens destroying forests, and their prominent inclusion in various host-pathogen indices reflects this importance. It is increasingly evident, however, that Phytophthora species are abundant in streams in healthy forests and widespread in forest soils causing cryptic diseases, in addition to their more traditional roles as aggressive pathogens. While their ecology in non-agricultural ecosystems remains poorly understood, we now know that a numerous and diverse, nutritionally complex community of Phytophthora...

Sudden oak death (SOD) has had a devastating impact on tanoaks (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh) in California and Oregon. Tanoaks are a key component of the forests in which they are endemic and are one of the few species that are both killed by Phytophthora ramorum and contribute to its spread. Tanoaks were little studied prior to the onset of the SOD epidemic, resulting in few intellectual or material resources on which to base a disease resistance research program. Since 2006, a comprehensive research program, centered on a common garden of open-polli...

Phytophthora ramorum has caused extensive oak (Quercus) and tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh) mortality in portions of the central and north coasts of California. In conjunction with stream and terrestrial surveys, aerial detection surveys have played a critical role in detection and monitoring efforts associated with sudden oak death (SOD) throughout these regions. Aerial surveys conducted by the U.S. Department of Agriculture Forest Service, Forest Health Protection, have consistently documented the extent and intensity of hardwood mortality...

The Oregon Department of Agriculture implemented the Grower Assisted Inspection Program (GAIP) for nurseries in 2007. Participants in GAIP adopted best management practices (BMP) for five critical control points (CCP) (used containers, irrigation water, soil substrate, potting media, and incoming plants), where foliar Phytophthora can be introduced into nurseries. The goal of this study was to determine the presence or absence of Phytophthora at four CCP in GAIP nurseries 3- to 4-years after implementation of the program. From January to March 2011, samples were collected from irrigation...

Oregon's sudden oak death (SOD) eradication program has focused its efforts upon the aggressive treatment of tanoak (Notholithocarpus densiflorus (Hook.& Arn.) Manos, Cannon & S.H. Oh) over all other host species in its efforts to control the spread of Phytophthora ramorum. Despite its known importance to the epidemiology of SOD as described in California, bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.) has been retained at some eradicated sites due to apparent lack of infection. Some of these trees have since been identified as harboring P. ramorum. Along with the retention of...

Phytophthora ramorum, a threat to eastern United States forests, has been found in waterways outside the boundaries of infested ornamental nurseries in states other than California and Oregon. Very little is known about what factors are conducive to its survival and sporulation in water. Water collected from various sources with different salinity was used to better understand what effect salinity has on the life cycle of P. ramorum and its ability to infect tissue. Water samples, collected from natural bodies of water in May 2010 that had measured conductivity values of 5.6, 30.5, 32.3,...