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Sudden Oak Death Update Sudden oak death (SOD) is caused by an exotic fungus-like organism of unknown origin. Outside western Europe it is limited in nature to the central California coast and Curry County in southwest Oregon. It causes cankers on red oaks and leaf spots and twig blights on dozens of herbaceous plants. It has been reported on plants and soil in nurseries from B.C. Canada, Washington, Oregon and California. A pest Alert on SOD is available at http://na.fs.fed.us/spfo/pubs/pest_al/sodeast/sodeast.htm On March 8, 2004 it was reported that Phytophthora ramorum, the causal agent in sudden oak death, was confirmed in Monrovia Nursery (LA County, CA), outside the previous quarantine area. Since then two additional nurseries have had confirmed positives for SOD. Plants from these three nurseries have been shipped to all 50 states and Puerto Rico. The plants in question are principally varieties of Camellia, although Viburnum, another host genus, also has been distributed. Since then a quarantine has been placed on all host plants originating from California. USDA APHIS and State Departments of Agriculture have primary responsibility in tracking down these plants, called "trace-forwards". The results of the immediate tract forwards indicates about 95% of the plants had been further distributed or sold. At the time of this writing, at least 17 states have had samples test positive for SOD. No states in our region have had confirmed positives. A rhododendron was confirmed positive in MD and a lilac in NJ from sources other than the implicated CA nurseries. APHIS and State Departments of Agriculture are conducting surveys of nurseries, greenhouses, and retail outlets, and testing using ELISA, PCR and culture. Molecular screening using nested PCR can detect P. ramorum, but sometimes results in false positives. Any initial positives must be confirmed by the APHIS lab in Beltsville, MD. The Forest Service in cooperation with States began a forest survey in 2003 based on the SOD risk map. Risk is based on the several variables including the presence of nurseries receiving plants from California, abundance of host plants, in particular Rhododendron and Kalmia (Mountain laurel), and climate. Regions that have mean winter temperatures below freezing are considered low risk areas. This was based on the requirements for growth of P. ramorum in culture, and may or may not be valid in nature. These surveys were conducted in the mid Atlantic states and Southern Appalachians, and no SOD was found. At least 11 species of plants and trees currently are being surveyed. The survey was to be expanded to moderate risk areas in 2004, but given what has happened, a significant expansion is underway. Surveys will now be conducted in all of our states, including 30 plots each in MI, WI, MN, and MO, 30 plots in IL and IA, and 30 plots in OH and IN. A plot consists of two 100 m transects. Observations are being made on understory plants and oaks. Suspect bleeding cankers on oak and leaf spots on understory plants will be collected and shipped to approved laboratories for testing using PCR. These plots will be located according to a hierarchy of priorities. The highest priority will be oak forests, with know host genera in the understory, surrounding nurseries that received plants from the California nurseries. Next is any forest with know host genera in the understory, and finally, any forest with oak. In the unfortunate event there is a positive PCR result, the plot will be revisited and more samples collected and tested. Before there is any confirmation of SOD, a positive PCR must be verified by APHIS. In the event that SOD is confirmed options are few. In Oregon, unsuccessful attempts have been made to eradicate SOD in an isolated forest setting. The area was clearcut and burned, however SOD was subsequently found on sprouts. Herbicides are now being considered, which complicates eradication efforts. The host list seemingly grows weekly, and the number of states reporting positive finds from this shipment is also likely to grow. Much is unknown about the capability of P. ramorum to become established in eastern hardwood forests, although northern and southern red oaks have been found to be susceptible. While this appears to be akin to closing the barn door once the horses have escaped, continued vigilance and immediate response is the only hope we have to possible eradicate an introduction. There are many websites to keep abreast of the latest developments, one with many links is: http://www.suddenoakdeath.org
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