Pest Alert: Sudden Oak Death Update (December 6, 2004)

On November 19, USDA, APHIS, PPQ confirmed Phytophthora ramorum, the pathogen causing sudden oak death, at two Connecticut nurseries. The Connecticut detections were made during trace forward investigations as a result of the Hines Nursery finds in Forest Grove, OR.
The total number of confirmed positive sites from the trace forward, national, and other surveys is now 172 in 22 States. The breakdown per state is: AL (3), AR (1), AZ (1), CA (53), CO (1), CT (2), FL (6), GA (16), LA (5), MD (2), NC (9), NJ (1), NM (1), NY (1), OK (1), OR (24), PA (1), SC (4), TN (2), TX (11), VA (2) and WA (25). Of 170 positive detections, at least 127 are associated with a large retailer that shipped infected plants nationwide in March 2004.

For the Massachusetts survey the UMass Plant Disease Diagnostic Lab in conjunction with MA Department of Agricultural Resources tested more than 300 samples by ELISA and culturing, and none were positive for P. ramorum.

The United States Forest Service (USFS) has conducted surveys near nurseries and within the forest environment. The Massachusetts Department of Conservation and Recreation worked with USFS to survey Massachusetts. As of November 22, 2004, the USFS has surveyed 681 nursery perimeters, collecting 3207 samples. To date none have tested positive for P. ramorum. The USFS has also surveyed 266 general forest locations, collecting 1310 samples. Two of those samples, from Golden Gate Park in San Francisco have previously been reported as positive.

Nearly all detections of P.ramorum have been in nurseries except in California and Oregon where P.ramorum is established in natural areas. A positive detection for P.ramorum in a mature Northern red oak tree (Quercus rubra) in a forested park in Nassau County, New York has recently come into question. USDA/APHIS, USFS, and New York State officials have extensively surveyed and tested the forested park and the suspect red oak. A positive detection was made using nested PCR. Nested PCR is the most sensitive method known for detection of P. ramorum, and is currently the only APHIS-PPQ validated method for PCR detection of this organism. No other detections were made and no P. ramorum was cultured. In environmental in California and Oregon the organism has always been cultured. The USFS determined the Nassau County find was a false positive. Because the organism could not be isolated through culture, USDA/APHIS has not quarantined the entire county. The preserve remains under an Emergency Action Notification and USDA/APHIS expects to continue monitoring the preserve for two years. After two years, if no further detections are made, USDA/APHIS will likely declare that P. ramorum is known not to occur in Nassau County, New York.

The pest alert is from the Massachusetts Introduced Pests Outreach Project, a collaborative project between the Massachusetts Department of Agricultural Resources and the UMass Extension Agriculture and Landscape Program aimed at preventing the establishment of new pathogens and pests in Massachusetts. Visit the project website (http://www.massnrc.org/pests) for more information on Sudden Oak Death and other emerging pests or to subscribe and unsubscribe for pest alerts.