Treesearch

The reuse of plant pots by nursery growers has repeatedly been shown to be a method by which transfer of plant pathogens within a nursery will occur. More critically, this practice is an efficient pathway to infest landscape settings or habitat restoration sites by the out-planting of pre-symptomatic infected plant material. The transfer of water molds (oomycetes), such as plant pathogenic Phytophthora species, is a major threat to restoration projects and prevention of cross-contamination via pots should be a critical nursery operational control. Our research has established performance...

We performed studies to determine the effect of leaf wetness on infection of whole plants of Rhododendron 'Cunningham's White' and Viburnum tinus by zoospores of Phytophthora ramorum. We also evaluated the effect of a post-inoculation drying period on infectivity of the two host species with zoospore inoculum. Twelve plants of each species were spray-inoculated with 50,000 zoospores/ml of nine combined P. ramorum isolates, and placed in a dew chamber at 20°C in darkness. Two plants were removed from the dew chamber after 0, 1, 2, 4, and 6 h incubation, and placed on a greenhouse bench to...

Leaves of California bay laurel (Umbellularia californica) are considered the primary natural source of inoculum for the devastating forest disease sudden oak death (Phytophthora ramorum), and yet this plant and the insects associated with its leaves remain understudied. This is unfortunate due to the role herbivorous insects may play in disease transmission and alterations to plant disease susceptibility. There is also a deficit of knowledge on how landscape-level variability or the effect of microclimate may influence insect presence and about systems involving both a plant’s pathogens...

The Forestry Commission-managed forest estate located in Plym, Devon (southwest England) was one of the first locations in late summer 2009 to have stands of Larix kaempferi (Japanese larch) confirmed as infected with Phytophthora ramorum (EU1 lineage). The 398 ha forest had a high proportion (>30%) of L. kaempferi showing catastrophic levels of P. ramorum infection with trees of all ages affected to some extent. Although a few infected rhododendron were present, larch was the primary sporulating host so all larch trees were removed from Plym forest between 2009-2011 as part of disease...

Phytophthora ramorum has spread and diversified throughout California’s northwestern coast since its introduction in the 1990s. Tracking the spread of P. ramorum and the functional response of the pathogen to the environment is of particular interest to managing the epidemic. Using genetic tools such as microsatellite markers, researchers have learned much of the pathogen’s epidemiology by identifying migrational pathways and new introductions. However, higher resolution markers may reveal previously undetected substructure. Work at the genetic and genomic level is underway to identify...

Phytophthora lateralis causes root rot of Port-Orford cedar (Chamaecyparis lawsoniana; POC) in native forests of northwest California and southwest Oregon and in landscape plantings of horticultural Chamaecyparis cultivars in the western US and Europe. In spring 2015, following observations of mortality amongst plant groups in two horticultural nurseries in Oregon, P. lateralis was isolated from the roots of two additional conifer species: Microbiota decussata and Juniperus communis. Species identification was confirmed by sequencing the ITS region using ITS4 and ITS6 primers. To substantia...

Infected nursery plants play an important role in the spread of Phytophthora ramorum , the causal agent of sudden oak death and ramorum blight. In order to minimize the risk for disease transmission to new areas, nurseries are inspected regularly for P. ramorum , and federal regulations require the eradication of infested plants and the disinfestation of nursery soil and equipment. The National Ornamentals Research Site at Dominican University of California (NORS-DUC) is a federally funded research nursery devoted to testing and developing environmental friendly management options for...

The National Ornamentals Research Site at Dominican University of California (NORS-DUC) was founded in the year 2009 by a Farm Bill grant to study Phytophthora ramorum in a sophisticated research nursery that reflects an authentic commercial nursery setting (www.dominican.edu/norsduc). NORS-DUC goals are to develop practical solutions for containment, remediation, and eradication of quarantine pathogens in nurseries and to reduce the risk of long-range spread of pests through infested nursery stock shipments. Research at NORS-DUC is conducted by a team of permanent staff as well as by P....

Soil solarization has been shown to be an effective tool to manage Phytophthora spp. within surface soils, but estimating the minimum time required to complete local eradication under variable weather conditions remains unknown. A mathematical model could help predict the effectiveness of solarization at different sites and soil depths. Prior research on solarization efficacy has focused on the minimum temperature and exposure time required to kill pathogens, and most mathematical models of the effects are based on cumulative temperature over time. However, two additional factors, soil...

CALinvasives is a web-based relational database and content management system (CMS) cataloging the statewide distribution of invasive pathogens and pests and the plant hosts they impact. The database has been developed as a collaboration between the Forest Pathology and Mycology Laboratory at UC Berkeley and Calflora. CALinvasives will combine information on the dispersal potential of pathogen and pest threats, the current location of each, the hosts threatened, and their distribution, making it possible to assess the risk posed by each existing and emerging threat to California’s native...