Difference between revisions of "Sudden Oak Death (SOD)"
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Fungicides are a preventative measure as no current fungicide can eliminate ''P. ramorum'' infections. However, it is advised to use fungicides only once all other management methods have been exhausted. Fungicides frequently mask SOD symptoms and make detection of the disease difficult. Additionally, fungicide-treated plants hiding symptoms could be sold and pose a contamination threat. | Fungicides are a preventative measure as no current fungicide can eliminate ''P. ramorum'' infections. However, it is advised to use fungicides only once all other management methods have been exhausted. Fungicides frequently mask SOD symptoms and make detection of the disease difficult. Additionally, fungicide-treated plants hiding symptoms could be sold and pose a contamination threat. | ||
− | == | + | ==Regulation== |
+ | ===Federal=== | ||
+ | |||
+ | The USDA Animal and Plant Health Inspection Service (USDA-APHIS) develops and mandates federal regulations regarding ''P. ramorum''. Additionally, USDA-APHIS determines the quarantine status of ''P. ramorum'' along the western coast.<ref>[http://www.suddenoakdeath.org/diagnosis-and-management/regulations/ California Oak Mortality Task Force]</ref> | ||
Several regulations regarding the movement of infected plants and hosts, quarantined and regulated areas, inspections, and nursery stock exist. These regulations are found under US Code of Federal Regulation, Title 7 (Agriculture), Part 301, Subpart ''Phytophthora Ramorum''.<ref>[https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=1&SID=36beb9336d8b90a8225b7196b3.567b10&ty=HTML&h=L&r=SUBPART&n=7y5.1.1.1.2.24#se7.5.301_192_66 US Government Publishing Office]</ref> | Several regulations regarding the movement of infected plants and hosts, quarantined and regulated areas, inspections, and nursery stock exist. These regulations are found under US Code of Federal Regulation, Title 7 (Agriculture), Part 301, Subpart ''Phytophthora Ramorum''.<ref>[https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=1&SID=36beb9336d8b90a8225b7196b3.567b10&ty=HTML&h=L&r=SUBPART&n=7y5.1.1.1.2.24#se7.5.301_192_66 US Government Publishing Office]</ref> | ||
+ | |||
+ | ===California=== | ||
+ | In California, the California Department of Food and Agriculture sets a statewide quarantine policy that interlocks with existing federal regulation. More information is available on the [https://www.cdfa.ca.gov/plant/pe/InteriorExclusion/SuddenOakDeath/ CDFA] website. | ||
==Current Research== | ==Current Research== |
Revision as of 05:07, 30 March 2017
This page discusses sudden oak death (SOD), an oak tree disease caused by the plant pathogen (Phytophthora ramorum).
Contents
Description
Sudden oak death (SOD) is a non-native forest disease that is believe to have originated from Asia and spread via international nursery trade. [1] The name of the disease is rooted in its initial discovery in 1995 when researchers in Marin County, California observed widespread rapid oak mortality.[2][3] Researchers later determined that SOD results from infection by Phytophthora ramorum, a type of water mold responsible for causing Ramorum Blight. [4]
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). 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.[5] Over 1 million trees have died due to SOD in Northern and Central California.[6]
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.
As of March 2017, there is no known cure for SOD.[7]
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.[8][9] 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.[10]
Cankers and "bleeding"
Cankers are brown, water-filled abrasions that form on the bark of infected trees. Frequently, these legions can penetrate into the xylem. Cankers can damage the tree bark, leading to fracturing of bark and tree girdling. These symptoms can accelerate declines in tree health and expedite tree death.[11]
Cankerous regions release viscous sap. This black to amber hued fluid seeps out in a process typically referred to as "bleeding". [12]
P. ramorum Hosts in California
While all hosts species can be infected by SOD, not all species die from infection. Several species act as carriers that can potentially transfer the pathogen to sensitive species. Several hosts of P. ramorum have been identified worldwide[13]. The known hosts in California[14] are:
Oak species
- Coast live oak (Q. agrifolia)
- California black oak (Q. kelloggii)
- Shreve's oak (Q. parvula var. shrevei)
- Canyon live oak (Q. chrysolepsis)
- Tanoak (Lithocarpus densiflora)
Non-oak species
- Madrone (Arbutus menziesii)
- Evvergreen huckleberry (Vaccinium ovatum)
- Manzanita (Arctostaphylos spp.)
- Ornamental rhododendron (Rhododendron spp.)
- Bay laurel (U. californica)
- Big leaf maple (Acer macrophyllum)
- Toyon (Heteromeles arbutifolia)
- Salmon berry (Rubus spectabilis)
- California buckeye (Aesculus californica)
- Coffeeberry (Rhamnus californica)
- Cascara (Rhamnus purshiana)
- California hazelnut (Corylus cornuta)
- Honeysuckle (Lonicera hispidula)
- Viburnum (Viburnum spp.)
- Poison oak (Toxicodendron diversilobum)
- Western starflower (Trientalis latifolia)
- Coast redwood (Sequoia sempervirens)
- Douglas fir (Pseudotsuga menziesii)
Prevalence in Central California
While SOD was first found in central California [15], the disease has not spread to every county in the central coast. A 2011 study of the distribution of SOD in California revealed that Santa Cruz and Monterey were the only central coast counties with confirmed cases of SOD [16]. However, a 2016 distribution map by OakMapper suggests that SOD might be more widespread throughout the central coast.
Impacts and concerns
SOD causes marked declines in oak woodland populations. It is estimated to double and quadruple the mortality of coast live oak and tanoak, respectively.[17]
Ecology
Declines in oak woodlands could have cascading ecological impacts. They serve as habitat for invertebrates and vertebrates. Reductions in oak populations could result in less nesting grounds for birds and negatively impact nesting success. The amount of acorns produced would also drop, resulting in marked declines in a food source some vertebrate populations may depend on.[18]
Spread of SOD
Particularly concerning is the potential spreading of SOD from infected regions to unaffected regions. Laboratory experiments have revealed that oaks species on the eastern coast of the United States can be infected by SOD.[19] These species include northern red oak (Quercus rubra), mountain laurel (Kalmia latifolia), sugar maple (Acer saccharum), black walnut (Juglans nigra), white oak (Quercus alba), and chestnut oak (Q. prinus).[20]
Commerce
Commerce of nursery and ornamental plants has changed after numerous studies suggested that the pathogen was introduced via nursery plant trade.[21] The changes are more prevalent with known hosts of SOD and in regions impacted by SOD. In California counties with SOD, hosts plants are thoroughly inspected before being transported out into unaffected regions.
However, containment of the pathogen is difficult. Some nurseries use fungicides that can eliminate symptoms of SOD but not the pathogen itself. In other cases, infected plants display no observable symptoms of disease.[22]
Humans
The California Oak Mortality Task Force provides guidelines on how anthropogenic spread of SOD can be reduced. These are:
- Stay out of infested wildlands during high risk times altogether.
- Don’t collect or transport host plant material from an infested or quarantined area.
- Avoid entering infested areas during wet conditions.
- Keep vehicles on paved and graveled surfaces when conditions are wet.
- Stay out of areas of wet soil and mud.
- If you do enter an infested area during wet conditions, check yourself, your pet(s), vehicle and equipment for accumulations of mud, soil, organic material, and detached plant leaves. Remove these accumulations before traveling to an area that is not infested.
- If you live in an area infested with P. ramorum, chances are some of your belongings may be contaminated by the pathogen. If you travel to an area that does not have the disease, be sure that the belongings that you take with you are clean – shoes, bicycles, pets, vehicle, etc.
Additional sanitation instructions for working in infested areas are also provided.
Management
Current management practices as outlined by the University of California suggest a three pronged approach: nursery management and monitoring, spread reduction efforts, and fungicides.
Nursery management
In nurseries concerned with SOD spread, the main priority should be preventing the introduction of the pathogen. Careful inspection of incoming stock can help minimize risk of introduction. Auxiliary efforts at disease prevention are careful monitoring of stock stored outdoors and withholding the use of fungicide when monitoring the infection status of plants.
Extra precautions should be taken if nurseries are located near SOD hosts or in regions with SOD presence. These include doing things like:
- Monitoring nearby host plants for signs of disease
- Building berms to prevent the movement of soil and water into the nursery
- If using irrigation water pumped from nearby streams and ponds, periodically checking it for contamination of P. ramorum.
Spread reduction efforts
Certain practices and monitoring efforts around infected areas can reduce SOD spread. Minimizing the period foilage is wet can reduce spread of SOD, as wet conditions are conducive for P. ramorum spread. Irrigation systems and sources should be carefully checked for any potential leaks, cracks, or presence of P. ramorum. Effort should be made to avoid mixing in soil or plant material from infected sites to uninfected sites. Tools should be carefully disinfected if they come in contact with infected soil or plants.
Fungicides
Fungicides are a preventative measure as no current fungicide can eliminate P. ramorum infections. However, it is advised to use fungicides only once all other management methods have been exhausted. Fungicides frequently mask SOD symptoms and make detection of the disease difficult. Additionally, fungicide-treated plants hiding symptoms could be sold and pose a contamination threat.
Regulation
Federal
The USDA Animal and Plant Health Inspection Service (USDA-APHIS) develops and mandates federal regulations regarding P. ramorum. Additionally, USDA-APHIS determines the quarantine status of P. ramorum along the western coast.[23]
Several regulations regarding the movement of infected plants and hosts, quarantined and regulated areas, inspections, and nursery stock exist. These regulations are found under US Code of Federal Regulation, Title 7 (Agriculture), Part 301, Subpart Phytophthora Ramorum.[24]
California
In California, the California Department of Food and Agriculture sets a statewide quarantine policy that interlocks with existing federal regulation. More information is available on the CDFA website.
Current Research
References
- ↑ 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
- ↑ California Oak Mortality Task Force
- ↑ UC BERKELEY FOREST PATHOLOGY AND MYCOLOGY LAB
- ↑ Sentinel Plant Network
- ↑ California Oak Mortality Task Force
- ↑ 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.
- ↑ 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
- ↑ Rizzo DM. 2003. Sudden Oak Death: host plants in forest ecosystems in California and Oregon. In: Proceedings of sudden oak death online symposium. American Phytopathological Society, http://www. apsnet. org/online/SOD
- ↑ Garbelotto M, Svihra P, Rizzo D. 2001. New pests and diseases: Sudden oak death syndrome fells 3 oak species. California agriculture 55(1):9–19.
- ↑ UCR
- ↑ Rizzo DM, Garbelotto M. 2003. Sudden oak death: endangering California and Oregon forest ecosystems. Frontiers in Ecology and the Environment 1(4):197–204.
- ↑ Rizzo DM, Garbelotto M. 2003. Sudden oak death: endangering California and Oregon forest ecosystems. Frontiers in Ecology and the Environment 1(4):197–204.
- ↑ Rizzo DM, Garbelotto M. 2003. Sudden oak death: endangering California and Oregon forest ecosystems. Frontiers in Ecology and the Environment 1(4):197–204.
- ↑ Don't Move Firewood
- ↑ University of Florida
- ↑ University of California
- ↑ California Oak Mortality Task Force
- ↑ US Government Publishing Office
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.