Treesearch

Sudden oak death, caused by the invasive oomycete pathogen Phytophthora ramorum, continues to shape the dynamics of coastal populations of oak (Quercus spp.) and tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh) in California and tanoak in southwestern Oregon. Over the last decade, high mortality rates have been reported in natural populations of coast live oak (CLO; Quercus agrifolia Née) in California, raising concerns for the integrity of important coastal ecosystems. However, it is now recognized that in spite of high infection and mortality rates, asymptomati...

Phytophthora ramorum-infested soils have been implicated as a source of primary inoculum in natural ecosystems. Implicit in this pathway is the need for infection of understory vegetation during pathogen establishment, preceding infection of bole hosts. In support of soil dispersal, studies using artificiallyinoculated soils have shown that understory inoculum can infect low-lying foliage of tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh) and California bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.) (Fichtner et al. 2009). The lack of association...

The Marin Municipal Water District's (MMWD) 7487 ha Mt. Tamalpais watershed in Marin County, California has the dubious distinction of being one of the earliest and most extensive areas impacted by Phytophthora ramorum in California. Rapid die off of tanoaks (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh) were first documented in 1995.With funding support from the U.S. Department of Agriculture Forest Service, MMWD initiated an assessment of landscape-scale changes in forest structure and understory floristics relative to P. ramorum spread in the Mt Tamalpais watershed...

With its high host mortality and ability to cause landscape-scale alterations in forest cover and composition, sudden oak death (SOD) (etiological agent Phytophthora ramorum, Stramenopila, Oomycota) mirrors past forest disease epidemics such as Chestnut Blight and Dutch Elm Disease. In contrast with these past epidemics, however, the appearance of SOD converges with a time of significant advancement in the development of molecular genetic tools that allow the movement of individuals (or individual genotypes) to be tracked and the role of evolutionary processes in disease progression to be...

We present a study of the epidemiology of sudden oak death (SOD) in California within a watershed based on temporally and spatially replicated surveys of symptoms, viability of the pathogen from symptomatic leaves, and genetic analyses using polymorphic SSR markers. Phytophthora ramorum is sensitive to climate; its optimal growth and transmission conditions are in the spring with warm rainy weather, and although it can survive and persist in harsh conditions, its capacity for transmission and dispersal are significantly reduced in drought conditions. Its main method of transmission is via...

In California, sudden oak death (SOD) treatment efforts have been localized, often targeting specific trees or properties. The widespread nature of SOD establishment and spread in coastal mountains of California has mostly precluded use of broader eradication strategies, which are more applicable in isolated infestations like those in Oregon. However, the 2010 detection of a new infestation in Redwood Valley, California—more than 80 km from the nearest known infestation, and the northernmost known occurrence in the state—presented an opportunity for the first attempt at containment and...

In 2006, three forested sites infested with Phytophthora ramorum in Humboldt County, California were subjected to different combinations of treatments designed to reduce inoculum and control spread. One treatment, consisting of removal of all California bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.) and tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh) trees, was applied at all three sites, and other treatments were applied as case studies at single sites. The sites were monitored for 6 years. Results to date suggest that the treatments that involved...

Forestry, agriculture, and native ecosystems face ever-increasing threats by invasive species. Not all introduced species are, however, invasive. In order to establish and persist in a non-native land, introduced species have to adapt to different environments, unfamiliar food, and predators. There are a number of examples where invasive species evolved quickly in non-native regions (Brasier 1995, Davis 2009), such as leg size of cane toad (Phillips et al. 2006) and leaf size of St John's wart (Maron et al. 2004). Large phenotypic variation has been observed in clonal lineages of the...

The recent determination that Phytophthora ramorum is causing bleeding stem cankers on Japanese larch (Larix kaempferi (Lam.) Carrière) in the United Kingdom (Forestry Commission 2012, Webber et al. 2010), and that inoculum from this host appears to have resulted in disease and canker development on other conifers, including western hemlock (Tsuga heterophylla (Raf.) Sarg.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), grand fir (Abies grandis (Douglas ex D. Don) Lindl.), and Sitka spruce (Picea sitchensis (Bong.) Carrière), potentially has profound implications for the timber...

Diagnosis of sudden oak death (SOD) in tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh) and susceptible red/black oak species (coast live oak, Quercus agrifolia Née; Shreve oak, Q. parvula Greene var. shrevei (C.H. Mull.) Nixon; California black oak, Q. kelloggii Newb.) is facilitated by the fact that infected trees commonly develop obvious bleeding bark cankers. In contrast, canyon live oak (Q. chrysolepis Liebm.) exhibits a different pattern of symptom expression, which has made it difficult to identify and document Phytophthora ramorum bole cankers in this...