Treesearch

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...

Control measures for forest Phytophthoras often focus on reducing the spread of infested soils, including closing roads and washing vehicles. Similar measures are suggested for Phytophthora ramorum, despite its evident aerial dispersal: stay out of areas of wet soils, and clean clothing and equipment when entering or leaving infested areas. It remains unclear, however, if these measures have limited the spread of P. ramorum in Oregon and California.

Tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, C.H. Cannon & S. H. Oh) is highly susceptible to Phytophthora ramorum. Symptoms include stem cankers, shoot dieback, and foliar blight. The mechanism by which P. ramorum kills the trees is not known, however. In this study we aimed to determine what physiological factors contribute to tanoak mortality when trees are infected with P. ramorum, and to investigate the relationship between elicitin secretion and disease symptoms. In growth chamber experiments, we investigated how photosynthesis, stomatal conductance, water usage, and...

Phytophthora ramorum, the causal agent of sudden oak death in California oak woodlands, poses a threat to woody plants in the rest of the United States, including the Gulf Coast area, which is regarded as a high-risk location. Several plant species native to Gulf Coast forests were tested for susceptibility to P. ramorum, including yaupon (Ilex vomitoria Aiton), spice bush (Lindera benzoin (L.) Blume), southern magnolia (Magnolia grandiflora L.), sweetbay magnolia (Magnolia virginiana L.), black willow (Salix nigra Marsh.), baldcypress (Taxodium distichum L.), Virginia creeper (Parthenociss...

Despite the presence of Phytophthora ramorum in northern and central California forests since at least 1994, asymptomatic coast live oaks (Quercus agrifolia Née) still remain in heavily infested stands. Coast live oak infection and mortality rates of 5 percent y-1 and 3 percent y-1, respectively, observed in long-term monitoring plots in Marin County, California give no indication that individual trees appear to evade infection. In some study plots, more than 50 percent of the mature coast live oaks have died since 2000.