Sudden Oak Death

Many of you may have read or heard of Sudden Oak Death. Here are some general guidelines set up primarily for nursery growers but many also be of use to the home gardener. Suspicious plants would be camellias or viburnum one to two years old brought from a California, Oregon or Washington source. Plants infected can have cankers on the trunk, lesions (spots) on the leaves, defoliation and twig dieback. At this time NC State is encouraging home gardeners to leave plants alone and contact your Extension Service for further instructions.

In the spring of 2004, Phytophthora ramorum cause of Sudden Oak Death (SOD) and Phytophthora blight in California and Europe was found on camellias at two nurseries in southern California in a region outside the regulated counties in CA. Prior to inspection of these nurseries, camellias and viburnums were shipped to more than 1200 locations in 39 states some of which were unknowingly infected with P. ramorum.

Through subsequent trace-forward inspections of these locations by the U.S. Department of Agriculture, Animal and Plant Heath Inspection Service, Plant Protection and Quarantine (USDA APHIS PPQ) working in cooperation with the North Carolina Department of Agriculture and Consumer Services, it was determined that eight of 44 locations in North Carolina with camellias still on site had received infected plants. A total of 54 locations in 11 states outside of California have received infected plant material as of May 2004.

Federal eradication guidelines (http://www.aphis.usda.gov/ppq/ispm/sod/pdf_files/confirmed_nursery_protocol.pdf) are being followed to destroy infected plants in North Carolina and elsewhere. What should North Carolina nurseries do to avoid future problems with this federally regulated pathogen? Be aware of the current host and associated host list for P. ramorum. USDA APHIS PPQ maintains the official list of hosts and associated hosts of P. ramorum on their web site at http://www.aphis.usda.gov/ppq/ispm/sod/.

Know the geographical source of plant material you buy. Since the pathogen has not been found, to date, in the United States in natural areas outside of the regulated areas in California and Oregon including a few nurseries in those states, the probable way for P. ramorum to be introduced to a North Carolina nursery is on infected plant material brought into the nursery from sources in California, Oregon, or Europe. As a result of the nursery outbreak in southern California, USDA APHIS PPQ has put in place a requirement that all nurseries in California that ship hosts of P. ramorum or associated hosts interstate must be inspected each year. A list of nurseries that have been inspected and are in compliance, i.e. P. ramorum was not detected, as well as those nurseries in California that currently have P. ramorum infected nursery stock can be found on the California Department of Food and Agriculture web site at http://www.cdfa.ca.gov/phpps/pe/sod_survey/.

The Oregon Department of Agriculture instituted a statewide survey of all nurseries in 2003 to confirm that P. ramorum was not present in Oregon nurseries. As a result of the survey one nursery was found with P. ramorum and infected nursery stock was destroyed to eradicate the infestation. Subsequent trace-forward surveys were done to recover and destroy plants shipped to other locations in Oregon and Washington by the nursery prior to the discovery of the pathogen at that nursery. Request a copy of the nursery inspection certificate if you buy plant material from Oregon nurseries.

In Europe, P. ramorum has become established in many nurseries. Again, know the source of plant material purchased from Europe and insist on a copy of an inspection certificate stating that the nursery has been certified free of this pathogen.

Take steps at the nursery to minimize the impact should P. ramorum be introduced. Host and associated host plant material brought into the nursery from a location where P. ramorum has the potential to occur, i.e. California, Oregon, Europe and some Canadian regions should be unloaded in a way that associated leaf debris falling to the grown can be swept up and bagged for disposal by burial or burning. Likewise, if the shipping truck is completely emptied at your site, collect and bag debris for disposal once the truck is unloaded. Designate an employee responsible for inspecting arriving hosts and associated hosts from high-risk areas to be sure foliar symptoms of Phytophthora dieback and blight are not present. This is important because even though a shipper may be compliant with their state agriculture department on a yearly basis, the pathology situation at a nursery can change within a week. Training sessions by Cooperative Extension plant pathologists and information on the Internet can help you become aware of Phytophthora foliar symptoms.

DO NOT DISPOSE OF SUSPECT OR INFECTED PLANTS OR PLANT DEBRIS IN YOUR CULL PILE AS THE PATHOGEN COULD MOVE INTO THE ENVIRONMENT. The goal of the federal regulation is to keep P. ramorum out of our eastern forests.

Newly arrived host and associated host plant material should be segregated from the general nursery population for at least a 60-day period favorable for plant growth and disease development (P. ramorum is most active at temperatures around 68 degrees F in the presence of moisture from rain or overhead irrigation).

Irrigation run-off from and rainfall on these plants should not be allowed to return to the retention basin used for general irrigation. Re-think the way you lay out your blocks of plants.

The Federal "Confirmed Nursery Protocol" (http://www.aphis.usda.gov/ppq/ispm/sod/) is very specific in the way "blocks" of infected plants are selected for destruction.

For more gardening information call the Wilson County Master Gardeners at 237-0113 or email at wilsonmastergardener@hotmail.com. Master Gardeners are in the office Mondays, Wednesdays and Fridays from 1-3 PM.

More information on Sudden Oak Death and Phytophthora ramorum in nurseries can be found at the following web sites:

* USDA APHIS Pest Detection and Management Programs

 (http://www.aphis.usda.gov/ppq/ispm/sod/)

* North Carolina Department of Agriculture and Consumer Services

 (http://www.ncagr.com/plantind/)

* California Oak Mortality Task Force

 (http://www.suddenoakdeath.org/)

* California Department of Food and Agriculture  

(http://www.cdfa.ca.gov/phpps/pe/sod_survey/)

* Oregon Department of Agriculture

 (http://oda.state.or.us/plant/ppd/path/SOD/index.html)

Date Created: 6/28/2004.