The USDA Animal and Plant Health Inspection Service (APHIS) keeps two lists of plants that can be infected with P. ramorum, the pathogen that causes Sudden Oak Death – one of “host plants” and another of “associated plants.” The plants on both lists have been infected with P. ramorum under “natural conditions” (i.e., outside the laboratory). For plants on the “host” list, the disease process has been replicated in the lab. Those on the “associated” list are still undergoing laboratory replication procedures. Both lists are constantly being updated (as lab work is completed, “associated” plants may move to the “host” list. When new plant species show symptoms of the foliar diseases and tests confirm that they are infected with P. ramorum, APHIS adds them to the “associated” list. The most recent addition to the “associated” list was Formosa firethorn, added in April. For the latest listings, Click here.

Plants currently on the P. ramorum host and associated lists:

Rhododendron species (including azalea)
Viburnums (10 varieties)
Camellia (four varieties)
Witch hazel
Horse chestnut
Mountain laurel
European beech
Northern and southern red oak (have been naturally infected in Europe)
European yew
Lilac
Drooping leucothoe
Evergreen huckleberry

—EH

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