Diagnostic keys Home, Extension Plant Clinics

Information to help identifiy plants at risk from infection by Phytophthora ramorum the cause of Sudden Oak Death

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  1. What plant or plants are affected?

a. If the plant is a camellia, viburnum, pieris, Vaccinium, kalmia, rhododendron, or lilac purchased since 2002 – go to 4.

b. The plant is adjacent to those listed in a.) above – go to 2

c. None of the above – unlikely to be P. ramorum. Do not submit sample.


  1. Is the plant a known P. ramorum host? See http://www.aphis.usda.gov/ppq/ispm/sod/usdasodlist.html for an up-to-date host list.

a. Yes – plant name appears on the list of hosts or associated hosts for P. ramorum, or plant belongs to the same genus as listed host or associated host – go to 3.

b. No – plant name does not appear on the list of hosts or associated hosts, nor does the plant belong to the same genus as listed host or associated host – unlikely to be P. ramorum. Do not submit sample.


  1. Is the plant a member of the oak family (red oak, pin oak, chestunt, chinquapin)?

a. Yes – go to 5.

b. No – go to 4.


  1. Does the plant display foliar symptoms of leaf spots, defoliation, or stem dieback similar to those shown on the photos of plants infected with P. ramorum? (see CD or some web resources, such as http://www.ncipmc.org/sod/)

a. Yes – contact County Dircector or Area Horticultural Agent for testing.

b. No – unlikely to be P. ramorum. Do not submit sample.


  1. If the plant is a member of the oak family, does it display the following symptoms?

a. Bleeding from the bark without wounds, cracks, or insect holes. Bleeding does not have a foul odor. In advanced stages of the disease, bleeding may be accompanied by widespread, rapid death of the crown -

      1. Ask question 1 for any plants in the nearby landscape that might have been purchased and planted since 2002. Also see http://msucares.com/pubs/infosheets/is1664.pdf

      2. Contact County Director or Area Horticultural Agent about submitting a sample.

b. No bleeding from the bark, or bleeding is associated only with wounds, cracks, or insect holes – unlikely to be P. ramorum. Do not submit sample.


Adopted from Jennifer Parke, Oregon State University and Susan Frankel, U.S. Forest Service.

Diagnostic keys Home, Extension Plant Clinics