Treesearch

Since the first finding of Phytophthora ramorum in England in April 2002, an intensive campaign, supported by the European Community (EC) and national legislation, has been conducted to locate and eradicate all interceptions and outbreaks of P. ramorum. A summary of the findings made during these surveys is presented, along with an initial analysis of progress towards eradication.

Regulation of Phytophthora ramorum, cause of sudden oak death and other diseases, has resulted in endless challenges for regulators, and the forest and nursery industries in the United States. This paper outlines the process used to design U.S. P. ramorum quarantines and explores some of the biological paradoxes presented by having to develop regulations for a recently discovered pathogen. Disregard for Koch’s postulates, limitations of PCR and cultural diagnostic techniques, the perils of basing rules purely on published literature, and the precautionary principle are discussed. The...

Sudden oak death (SOD) was first discovered in Oregon forests in July 2001 near the city of Brookings. Since September 2001 we have been attempting to eradicate the pathogen by cutting and burning all infected host plants and adjacent apparently uninfected plants. Eradication currently is in progress on approximately 42 sites, totaling 72 acres. The majority of sites are on private land. All eradication funding has come from the USDA Forest Service.

While there is a great deal of scientific uncertainty about the nature and control of Phytophthora ramorum, there is growing concern that its economic costs will be significant. Indeed the repercussions at the nursery level of a positive test for the presence of P. ramorum may include severely impacted current and future cash flows. Given this possibility, nurseries that are susceptible to P. ramorum infestation may reassess their production strategy. Firms may choose to increase expenditures to prevent P. ramorum infestation, or they may choose to reduce production of P. ramorum host...

The survival rate of Phytophthora ramorum was assessed when introduced at high rates into composts of varying provenance and curing time, produced by both "turned windrow" and "forced air static pile" techniques. Survival in some compost media was high and statistically indistinguishable from positive controls (P

The native oaks of California are remarkable for being among the oldest and largest oak trees in the United States besides their great age and size, these trees possess various idiosyncrasies in their arrangements and shapes that appear to defy basic principles of ecology and population biology. When taken together, these and other associated patterns present an anomalous situation that cannot be explained using our current scientific understanding of old-growth forests. In this paper I describe several abnormal features of California oaks recorded during ecological surveys in the Coast...

Coast live oak (Quercus agrifolia) is a major species at risk in the current Phytophthora ramorum epidemic in California’s oak woodlands. To search effectively for resistant genotypes, it is imperative to have an understanding of the existing host population genetic structure in these forests, and how its reproductive capacity may be affected by major losses. The purpose of our study is to assess and quantify the distribution of genetic variation of coast live oak in central California. To understand the factors that may limit the ability of these populations to recover, we will compare...

In autumn 2002, we conducted a retrospective study on coast live oak (Quercus agrifolia) failures in Marin County, California, woodlands affected by Phytophthora ramorum canker (sudden oak death). The objectives of this case-control study were to quantify levels of bole, large branch, and root failure in these woodlands and determine how various tree and stand factors are related to failure potential. Non-failed trees were used as a control population to identify factors that might contribute to tree failure. Rates of bole and large branch (more than 20 cm diameter) failures were significan...

Removing trees inflicted with the sudden oak death (SOD) disease is often necessary because of hazard issues or homeowner/landowner desires. An alternative to disposal of this material is to find acceptable uses for this diseased material. A series of studies is being conducted to help understand the risk of spreading the Phytophthora ramorum infested wood through disposal and utilization activities. Two collection yards were set up in California for wood suspected of being infected with P. ramorum, one in Marin County and one in Santa Cruz County. More than 1,155 tons of woody, P. ramorum...

Early detection monitoring is essential for successful control of invasive organisms. Detection of invasions at an early stage of establishment when a population is small and isolated makes eradication more feasible and less costly. Sudden oak death, caused by the recently described pathogen Phytophthora ramorum, is an emerging forest disease that has reached epidemic levels in coastal forests of central and northern California. To control the spread of the pathogen and protect susceptible habitats, California has established an extensive monitoring program focused on early detection of...