Sudden Oak Death

Carlos Martinez, State Plant Health Director, USDA APHIS PPQ
Tuesday, March 16, 2004

Phytophthera ramorum, the causative organism in Sudden Oak Death, was found and confirmed in Monrovia Nursery in Azusa, California (Los Angeles county) on Monday, March 8, 2004 from samples collected as part of the PPQ National Survey. California Department of Food and Agriculture plant pathology laboratory confirmed Phytophthora ramorum, causal organism for sudden oak death (SOD)., In addition, presumptive positives have also been found in 12 other nurseries in southern California. The nurseries are located in Los Angeles, San Diego, and Orange counties. Testing to confirm the presence of Phytophthera ramorum in these additional nurseries should be completed during the week of March 16, 2004. It must be stressed that as of today only one nursery has cultured positive for SODS. However, there is a 90% chance that the others will also culture positive.

The confirmed positive nursery is one of the nurseries owned by Monrovia Nurseries in Los Angeles County. That nursery is a 500 acre facility that specializes in Camellias. Approximately 40 acres of the nursery are planted with Camellias. We are working with California Department of Food and Agriculture which quarantined the nursery on March 9, 2004.

The presence of P. ramorum was unexpected because this nursery is not in the regulated area, nor susceptible to spread because it was not near any source of known infection. The nursery is situated in a dry climate, whereas previous detections of the organism have been confined to areas with a wet environment. The disease appears to be present in this nursery in at least two different species; camellia and viburnum.

There are no regulatory treatments that are efficacious for treating plants against this disease. Based on technical information provided by PPQ, Center for Plant Health, Science and Technology, the disease can be mitigated in a nursery environment through the application of fungicidal sprays, but there is no control once nursery stock are placed into the environment.

This discovery is significant because the disease has been found in an area that is atypical for predicting the establishment of P. ramorum; it has been found in a large nursery that ships stock throughout the U.S.; and trace forwards will be extensive and challenge current resources.

Approximately 28,000 suspect plants from Monrovia Nursery in Azusa, CA have been shipped to nurseries in Georgia. Georgia Department of Agriculture and USDA, Plant Protection and Quarantine personnel are in the process of visiting these nurseries. During the visits inspectors will place holds on any suspect material, inspect the plants for any sign of disease, and collect information from the nursery owner. Any samples collected will be submitted to CES Pathologist Jean Woodward for testing. Anyone needing additional information is encouraged to contact Mike Evans, GDA (404- 656- 9379) or Carlos Martinez, PPQ (770-922-9894).