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Sudden Oak Death (SOD) Alert

April 7, 2004

This disease causes a wide range of symptoms on forest and nursery plants. In general, symptoms are of two types: bark cankers that may kill the host and foliar blights that may serve as a reservoir for the pathogen. The host range covers 59 host species.

Last August, when we wrote about SOD, we did not believe this pathogen was going to come to the Midwest anytime soon. Some details about the disease can be found in the 2003 issue 15 of this newsletter. At that time, the pathogen, Phytophthora ramorum, had not been found in the United States outside of California and Oregon. That is no longer true.

On March 8, 2004, Phytophthora ramorum was confirmed on six varieties of camellias at a nursery in southern California. Since then, other nurseries have also been involved. Plants from these nurseries were sold and shipped to other states. USDA’s Animal and Plant Health Inspection Service (APHIS) staff has been working since March 8 to track shipping records to other states. Each state plant-health regulator now knows which nurseries received shipments from confirmed infection sites. Those nurseries have been or will be inspected. Plants that remain in the nurseries have been placed on hold until they can be tested for Phytophthora ramorum. In many cases, however, shipments have been sold to the public and are untraceable. California nurseries have cooperated to help get this disease under control, and many plants have been destroyed. As of March 26, 2004, APHIS has regulated the interstate movement of Phytophthora ramorum hosts from all California nurseries.

Recently, three positive cases of Phytophthora ramorum were confirmed in north Florida on camellias that originated at a southern California nursery. In Illinois, only eight nurseries received shipments of plants. Three now have plants on hold until sampling and testing can be completed. At this point, Phytophthora ramorum has not been identified in Illinois.

Because this disease can cause symptoms that range from cankers to leaf blights, it can be hard to confirm. The USDA will be launching a national survey to determine whether Phytophthora ramorum is present in areas of the United States other than California and Oregon. The UI Plant Clinic will assist in testing Illinois samples. In Illinois, it is more likely that the disease will appear first on shrubs that have foliar infections rather than trees with canker infections. Spore formation on foliar hosts can serve as inoculum to other plants and so is of greater concern. Still, many details of spread, infection, and host range are not known. The list of regulated foliar hosts is very long and still expanding. Included are Vaccinium spp., Rhododendron spp., honeysuckle, Viburnum spp., Camellia spp., and Pieris, but the list goes on.

For more information about SOD, visit the APHIS Web site at http://www.aphis.usda.gov/lpa/issues/sod/sod.html or the APHIS PPQ (plant protection and quarantine) SOD Web site at http://www.aphis.usda.gov/ppq/ispm/sod.

Also, concise information is presented in a fact sheet on SOD produced by the North Central Region Pest Management Center at http://www.ncpmc.org/sod/.

At this point, SOD has not been found in Illinois, and this article is intended as an alert. In upcoming issues, we will announce findings of Illinois testing. You can also check the references above for updates. If you have a plant sample that you think is suspect, call your Extension educator before sending a plant sample to a lab. The University of Illinois Plant Clinic opens May 1 and will be ready to test for this pathogen. Whenever dealing with unknown pathogens of this type, place plant samples in a double layer of zip lock bags to prevent potential spread of spores. Seal box cracks with strapping tape. New information about SOD and its spread will be provided in upcoming issues.

Author: Nancy Pataky


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