Treesearch

In a four year project, three different filtration systems were tested under commercial nursery conditions to eliminate Phytophthora spp. from irrigation water. Five nurseries were involved in the project. Slow sand filtration systems were tested in three nurseries. In the fourth nursery, a filtration system with lava grains (Shieer® Bio filtration) was tested and in the fifth nursery, a constructed wetland was investigated. The average filtration capacities per year (2003 until 2005) were between 30,000 and 100,000 m³ water for the three sand filtration systems, about 46,000 m³ for the...

It is generally thought that extensive periods of flooding can predispose plants to infection by Phytophthora pathogens. We evaluated the effect of 0, 1, 3, and 7 days of flooding before infection of Rhododendron plants through either wound inoculation of leaves or infestation of the potting mix using two hybrid cultivars ?Catawbiense Boursault? and ?Minnetonka?. Foliage was inoculated with zoospores and potting mix was infested with both zoospores and mycelial agar plugs. Lesion area was quantified using digital imaging. Flooding had no effect on lesion area of foliar infections. Sporangia...

Pathogen effectors can serve a virulence function on behalf of the pathogen or trigger a rapid defense response in resistant hosts. Sequencing of the Phytophthora ramorum genome and subsequent analysis identified a diverse superfamily of approximately 350 genes that are homologous to the four known avirulence genes in plant pathogenic oomycetes and share with them two protein motifs (RxLR and dEER). These have been termed Avh (avirulence homolog) genes. While as a whole the genes in this superfamily exhibit modest sequence similarity, small groups of closely related genes can be identified....

Phytophthora ramorum, the causal agent of sudden oak death (SOD) is a quarantine pathogen that has forced the implementation of extraordinary measures to track and contain the movement of infected nursery stock both within and outside of the three western states of California, Oregon and Washington. Federal guidelines in the United States for diagnostic testing of P. ramorum are in place to insure the sensitivity and reliability of detection tests. PCR assays are used to determine whether the Phytophthora sp. detected by the initial immunoassay screening is P. ramorum. Most of the time...

On behalf of the United States Department of Agriculture (USDA)-Forest Service, Pacific Southwest Research Station and the California Oak Mortality Task Force, it is my pleasure to welcome you to the Sudden Oak Death Third Science Symposium. Looking back at the first sudden oak death science symposium held in Monterey in December 2002, it is amazing to see how far we have come in such a short period of time. It is hard to believe that at that point—a little over four years ago—we didn't even know Camellia was susceptible to Phytophthora ramorum.

It was the second week of June, 2000, the hottest weather on record in San Francisco - hardly Phytophthora weather. But it was that week, at China Camp State Park, that Dave Rizzo and colleagues collected the bark samples from bleeding cankers on coast live oaks that finally moved sudden oak death (SOD) from the “cause unknown” category to “Phytophthora disease” (Rizzo and others 2002). Research progress has been dramatic in the last seven years. Think of the advances in Phytophthora genetics, capped by publication of the complete genome sequence, and its applications in diagnostics and...

Sudden oak death (SOD), caused by Phytophthora ramorum, was first discovered in Oregon forests in July 2001. Since then an interagency team has been working with landowners to eradicate the pathogen by cutting and burning all infected and nearby host plants. During the first two years of the eradication effort, all host vegetation within 15 to 30 m of infected plants was destroyed. In recent years this distance has been increased to at least 100 m, reflecting recent research findings on spread of the pathogen. On private land, all tan oaks (Lithocarpus densiflorus) are injected with...

Following the recognition that Phytophthora ramorum (the cause of sudden oak death in the U.S.) was present in Europe as well as America, emergency European Community (EC) phytosanitary measures were put in place in September 2002 to prevent spread of P. ramorum, and also to stop introductions of the pathogen from elsewhere. A 3 year European project then started in 2004 to assess the risks posed by P. ramorum to trees and environmentally important habitats in Europe. The project ? ?Risk Analysis of Phytophthora ramorum?, known by the acronym RAPRA, involves eight research organizations in...

Phytophthora ramorum, the pathogen responsible for sudden oak death, also impacts the ornamental nursery industry, enhancing the potential for long-distance pathogen transmission in asymptomatic roots or in infested potting media. Soil borne populations of another nursery pathogen, Phytophthora parasitica, are suppressed by aluminum (Al)-amended peat, a system where Al activity is regulated by the formation of stable surface complexes with the organic matrix. Organic matter serves as an Al sink, regulating Al activity at a lower level than that predicted by the solubility of Al-bearing...

When we examine the nursery survey data over the past 3 years, we find that in the western states, the number of Phytophthora ramorum-infested nurseries found via nursery inspections or surveys has dropped by more than 0 percent from 2004 to 2006, from 110 nurseries to 50, respectively. The percent of nurseries found to be infested compared to the number of nurseries inspected was at 1 to 2 percent. There were three main factors that were responsible for, or influenced, the decline from 2004 to 2006: 1. The sudden oak death Federal Order which was signed in 2004 and implemented in January...