The COMTF Nursery Committee was created in the Fall of 2002. It brings
together industry representatives, CDFA, USFS, USDA and European regulators from across the globe to identify critical research needs relevant to Sudden Oak Death (SOD) in the nursery industry. Co-Chairs
Karen Suslow, 530/795-6030, ksuslow@hineshort.com
Gail Raabe, 650/363-4700, SMateoAg@cdfa.ca.gov 2003 SOD Overview Best Management Practices (BMP's) (.pdf. 125 kb)
Nursery Research Needs (.pdf, 80kb) Nursery Focus Group (.pdf, 73kb)
Update: December 03 - January 04 (.pdf, 109kb) Update: October 03 (.pdf, 79kb)
Update: July - August 03 (.pdf, 117kb) Update: June 03 (.pdf, 106kb)
Update: March 03 (.pdf, 70) 2003 SOD Overview – Nursery Committee Karen Suslow and Gail Raabe, Co-chairs COMTF Nursery Committee The COMTF Nursery Committee was created in the Fall of 2002. Shortly thereafter in December, a pivotal meeting was held in Monterey, CA, at which time industry representatives, CDFA, USFS, USDA and European regulators from across the globe identified critical research needs relevant to Sudden Oak Death (SOD) in the nursery industry. By June of 2003, the combination of researchers, the research projects and funding resources from the Forest Service and ARS-USDA
resulted in the initiation of many priority projects. Research: Nursery research projects have been underway for approximately six months. (Addendum A). In March 2004, research updates will be provided at a SOD conference at
Sonoma State University. As scientific data is made available, new questions emerge and the nursery industry needs to be positioned to respond to these challenges. SOD Host plants and associated host plants: The two host lists above serve different purposes.
The SOD host list was created to identify those plants that were found to be naturally infected with Phytophthora ramorum, the causal agent of SOD. Once Koch's Postulates were successfully completed for each plant, that host is added to the list. The associated host list
contains plants that have been force- inoculated with the pathogen (e.g. azaleas) or have been found to be naturally infected with the pathogen, but Koch's Postulates have not been completed. The USDA regulates the movement of the plants on the SOD host list only. However, if a nursery produces plants that appear on both lists, then all are inspected and
treated identically as it relates to holds and destruction requirements. CFIA (Canada) regulates all plants on both lists, at the genera level. The host list and associated host list were greatly expanded in 2003. Plants identified in Europe as infected with the A1 mating type are being rapidly added to the associated host list. U.S. nurseries should
not be purchasing any plants from SOD-infected nurseries in the European Union. There is no effective fungicide for the A1 (European) mating type; therefore, purchasing even non-host plants from an infected nursery is an extremely risky practice. Canada: CFIA no longer regulates the entire State of CA, just the 12 regulated counties. Humboldt and Contra Costa Counties were added to the list of regulated counties this year. USDA SOD-free place of production: Nurseries in the regulated counties that qualify as USDA SOD-free places of production are allowed to ship outside of the country. (Document found at www.suddenoakdeath.org ) Delimitation: A pilot project is under way in Humboldt County to delimit the SOD find. The infection site is limited in scope and removal of the trees is underway in February 2004. The expectation is that this will establish a precedent for other counties, with similarly limited SOD finds, if they can meet the stringent protocols. European mating type A1 versus North American mating type A2: In 2003, both mating types were found in Europe, Canada and in the Pacific Northwest. Additionally, the first Phytophthora ramorum infected native vegetation was reported in Europe in 2003. Until the native vegetation find, the A1 type was considered to be only an aggressive nursery pathogen and not known to occur outside of the nursery environment.
Fungicides: Research on the performance of fungicides for the control of P. ramorum is underway. Results may appear promising for control of the A2 (North American) mating type. However, performance data on these same
fungicides for the control of the A1 (European) mating type show no useful efficacy. Masking of the A2 P. ramorum symptoms was observed as a result of using Phytophthora-specific fungicides. Further work is being conducted in this arena. Finds in the western US: As was predicted by Dave Rizzo, 2003 was a la Niņa year and many nursery infections occurred in the western U.S.. Transfers and buy-ins were the key methods by which the pathogen spread within the nursery industry. Nursery practices that result in extended leaf wetness and humid environments, such as overhead irrigation in shadehouse structures, may prolong the window of opportunity for infections to
occur. Expect to see more nursery finds as the intermittent rainy season continues in 2004 The first nursery find in a non-regulated county in CA occurred in 2003. Upon investigation, it would appear that the only plausible mode of exposure and/or transport of P. ramorum propagules was on the shipper's own trucks. Inoculum may have been acquired during the plant delivery process by transport equipment or on returned plants from infected nursery growing-grounds in regulated counties, upon return to the shipper facility.
Best Management Practices for the nursery industry: The BMPs developed by CDFA, County Agricultural Commissioners and the CA nursery industry were accepted by the USDA in their fourth draft of the infested nursery protocol. COMTF hosted a
training/workshop in February in northern and southern CA where the nursery BMPs were reviewed and discussed. ADDENDUM A
Nursery Subcommittee Research Needs developed at the Monterey SOD Symposium in December 2002 Revised 4-23-03 by CDFA (Nick Condos, Kathy Kosta); San Mateo Ag. Comm. (Gail Raabe) and Nursery Subcommittee Co-chair (Karen Suslow)
Nursery research that needs to be accomplished in order to: - develop regulations to prevent or reduce the risk of introduction or spread of Sudden Oak Death by the causal agent, Phytophthora ramorum
- position the industry for creation of pest-free production sites in the regulated CA counties
1. Determine if potting media and/or the components will harbor P. ramorum propagules. a. Are reproductive propagules of P. ramorum found in sawdust, sand and other potting soil components and are they viable? What types of propagules are found? b. How long do they remain viable? c. Can these potting soil components support the growth and reproduction of the pathogen if introduced into the finished potting media?
1a, 1c: Bob Linderman and Jennifer Parke (ARS – Corvallis, OR); 1b: Nina Shishkoff (ARS – Ft. Detrick, MD)
2.
Development of rapid field detection techniques/protocols for sampling of irrigation water and soil for the presence of P. ramorum at nursery facilities. Jim MacDonald (UC Davis) 3. Confirm Koch's postulate on regulated hosts strictly according to the definition of the procedure, including use of the isolate extracted from the same type of
host, reproduction of the symptoms seen on the original specimen, re-isolation of the pathogen and confirmation that it is P. ramorum. Determine if the regulated hosts are dead-end hosts* or sources of inoculum (dead-end host= continuous dissemination of the pathogen is not possible due to various reasons: secondary propagules are not produced, or not disseminated or the titer is too low due to physiological reasons ….) How much of a risk do these crops pose?
Paul Tooley and Nina Shishkoff 4. Determine the effectiveness of fungicide treatments on nursery stock. a. Does the use of fungistats and fungicides mask the appearance of P. ramorum symptoms on nursery stock?
b. If so, for what length of time will the symptoms be masked? c. How effective are fungicides; will they kill spores on the surface of a container?
Nina Shishkoff
5. Determine what is effective against P. ramorum and at what rates: a. Ozonation of water b. Chlorination of water c. …
6. Determine if P. ramorum can successfully move from the soil in a potted plant to infect and cause disease in another plant, thereby demonstrating spread of the pathogen. a. What level of inoculum is needed to cause a new infection? b. What is the threshold level? c. How well do detached leaf inoculation assays correlate to the risk
of a natural infection? 6a, 6b - Paul Tooley and Nina Shishkoff
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