Treesearch

A total of 33 host species commonly found in eastern (8) and western (25) Canadian landscapes and forest sites were selected for this study. Detached leaves/needles were inoculated with Phytophthora ramorum EU2 lineage mycelia which was isolated from stream bait near an infected larch plantation in Scotland, UK. There was a large variation in susceptibility among hosts. Among the non-conifer hosts, Pacific dogwood, manzanita, camellia, rhododendron and salal in western Canada and sumac, yellow birch, wintergreen and white ash in eastern Canada were the most susceptible to P. ramorum EU2...

There is a continuing desire to investigate the potential of biological control to manage the spread of Phytophthora ramorum. A specific isolate of Trichoderma asperellum has been demonstrated to be effective in reducing P. ramorum soil populations to non-detectable levels. This study was conducted to investigate the interaction of different T. asperellum application rates with different initial soil populations of P. ramorum in a mock nursery setting and to investigate the impact of these interactions on important enzyme levels. Field trials were set up in the fall and spring where soil...

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...

The exclusion of anthropogenic fire is a primary factor responsible for the ‘mesophication’ of eastern oak (Quercus) forests and resultant oak regeneration problems. Consequently, the reintroduction of fire is increasingly used to promote the establishment and growth of oak and hickory (Carya) and control competition from shade-tolerant species (e.g., red maple (Acer rubrum)) in the forest understory. In this study, we examined the effects of fire frequency on the abundance of prominent species in the woody regeneration layer in oak-dominated forests of eastern Kentucky. Treatments...

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...