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Revision as of 01:57, 30 March 2017
This page discusses sudden oak death (SOD), an oak tree disease caused by the plant pathogen (Phytophthora ramorum).
In addition to SOD, Phytophthora ramorum also causes Ramorum Blight. Phytophthora ramorum was first documented in Central California in the mid-1990s, and has since caused severe mortality of several oak tree species and most notably tanbark oak (Notholithocarpus densiflorus). In 2014, Phytophthora ramorum was estimated to extend from Santa Barbara in California to Curry County in Oregon [1]. The disease has been found worldwide. It is speculated that the disease spread world-wide via the nursery industry. Currently, restrictions exist on the movement of nursery plants, firewood, and soil to minimize the spread of the disease.
The disease was named in the mid-1990s when oak and tanbark oak trees suddenly and simultaneously exhibited signs of distress and subsequently died [2]. The severe die-back of the species gained public and political attention, and subsequently the California Oak Mortality Task Force was formed to identify the cause of the oak deaths. Today the California Oak Mortality Task Force coordinates research, monitoring, management and education of SOD.
Phytophthora ramorum affects many plant species. Phytophthora ramorum can infect and cause mortality in the following species: coast live oak, California black oak, Shreve oak, and canyon live oak, as well as tanoak trees. Phytophthora ramorum can causes twig and foliar diseases in species such as California Bay laurel, Douglas-fir, and coast redwood. These species are often hosts of pathogen, primarily responsible for the pathogen's dispersal, but themselves do not die from the disease. Implications of SOD spread include loss of habitat, loss of food sources for wildlife, increase in exposed soils, and changes in the frequency and intensity of wildfires.
Phytophthora ramorum thrives in cool, wet climates [3]. Phytophthora ramorum is a water-borne pathogen that disperses via fog, wind, water droplets, streams and splashing.
Contents
Background
Sudden oak death (SOD) is a non-native forest disease that is believe to have originated from Asia and spread via international nursery trade. [4] The name of the disease is rooted in its initial discovery in 1995 when researchers in Marin County, California observed widespread rapid oak mortality.[5][6] Researchers later determined that SOD results from infection by Phytophthora ramorum, a type of water mold responsible for causing Ramorum Blight. [7]
P. ramorum affects many plant species. It can infect and cause mortality in coast live oak (Quercus agrifolia), California black oak (Quercus kelloggii), Shreve oak (Quercus parvula var. shrevei), canyon live oak (Quercus chrysolepis), and tanoak (Lithocarpus densiforus). P. ramorum can also cause twig and foliar diseases in species such as California Bay laurel (Umbellularia californica), Douglas-fir (Pseudotsuga menziesii), and coast redwood (Sequoia sempervirens). These species are often hosts of pathogen, primarily responsible for the pathogen's dispersal, but themselves do not die from the disease.
Oak species vary in their susceptibility to P. ramorum infection. Tanoak and coast live oak have poor resistance to infection and experience high mortality rates.[8] Over 1 million trees have died due to SOD in Northern and Central California. [9]
Symptoms
Foliar Blight
Foliar Blight and branch die-back are some of the early indicators of infection. One of the earliest indicators are a "Shepherd's Crook", or wilting of apical shoots. Other foliage-related symptoms include brown blotches on leaves, rapid browning leaves throughout the crown, tip droop and die-back, and branch die-back caused by branch cankers.[10][11] These symptoms, particularly the browning of the crown, occur 2 to 4 weeks after infection. However, trees typically do not die immediately after these symptoms appear. The latency period between foliar blight and death is around two years.[12]
Trunk cankers and "bleeding"
Phytophthora ramorum Hosts
Prevalence in Central California
Impacts
Ecology
Commerce
Humans
Management
Distribution and efficacy of remediation
Laws
Current Research
References
- ↑ Citation needed
- ↑ Garbelotto M. and Hayden KJ. 2012. Sudden Oak Death: Interactions of the Exotic Oomycete Phytophthora ramorum with Naïve North American Hosts. Eukaryotic Cell: 11(11):1313.
- ↑ California Oak Mortality Task Force
- ↑ US National Park Service
- ↑ US National Park Service
- ↑ (USDA) Department of Agriculture (US). 2003. Sudden Oak Death (SOD). UPlant Materials Technical Note. Montana: USDA. Available from: Technical Note Plant Materials MT-44
- ↑ California Oak Mortality Task Force
- ↑ UCR
- ↑ UCR
- ↑ UC BERKELEY FOREST PATHOLOGY AND MYCOLOGY LAB
- ↑ Sentinel Plant Network
- ↑ California Oak Mortality Task Force
Links
Disclaimer
This page may contain student work completed as part of assigned coursework. It may not be accurate. It does not necessary reflect the opinion or policy of [CSUMB], its staff, or students.