Understanding and Managing Sudden Oak Death in California

SIDEBAR 1-2—Native Foliar Hosts of Phytophthora ramorum

As research has continued, the list of plants known to be susceptible to P. ramorum has expanded. An up-to-date host list is available at http://www.suddenoakdeath.org. Table 1-2 lists native trees, shrubs, and herbaceous plants that have been found with P. ramorum infections on leaves or twigs under field conditions. These hosts develop minor to significant canopy dieback, but are not killed by P. ramorum.

Table 1-2—California native forest species that develop Phytophthora ramorum leaf or twig infections (foliar hosts)

Scientific name Common name
Abies concolor1 White fir
Abies grandis1 Grand fir
Abies magnifica1 Red fir
Acer circinatum1 Vine maple
Acer macrophyllum Bigleaf maple
Adiantum aleuticum Western maidenhair fern
Adiantum jordanii California maidenhair fern
Aesculus californica California buckeye
Arbutus menziesii Pacific madrone
Arctostaphylos columbiana1 Hairy manzanita
Arctostaphylos manzanita Whiteleaf manzanita
Berberis diversifolia (= Mahonia aquifolium)1 Oregon-grape
Calycanthus occidentalis1 Spicebush
Ceanothus thyrsiflorus1 Blueblossom
Clintonia andrewsiana1 Andrew’s clintonia bead lily
Corylus cornuta1 California hazelnut
Dryopteris arguta1 California wood fern
Frangula californica (=Rhamnus californica) California coffeeberry
Frangula purshiana (=Rhamnus purshiana) Cascara
Fraxinus latifolia1 Oregon ash
Garrya elliptica1 Silk tassel tree , coast silktassel
Gaultheria shallon1 Salal, Oregon wintergreen
Heteromeles arbutifolia Toyon
Lonicera hispidula California honeysuckle
Mahonia nervosa Creeping Oregon grape
Maianthemum racemosum (=Smilacina racemosa) False Solomon’s seal
Osmorhiza berteroi1 Sweet Cicely
Phoradendron serotinum subsp. macrophyllum2 Mistletoe
Pseudotsuga menziesii var. menziesii Douglas fir
Rhododendron spp. Rhododendron
Rosa gymnocarpa Wood rose
Rubus spectabilis1 Salmonberry
Sequoia sempervirens Coast redwood
Taxus brevifolia1 Pacific yew
Torreya californica1 California nutmeg
Toxicodendron diversilobum1 Poison oak
Trientalis latifolia Western starflower
Umbellularia californica California bay, California laurel, pepperwood, Oregon myrtle
Vaccinium ovatum California huckleberry
Vancouveria planipetala1 Redwood ivy, redwood insideout flower

Source: U. S. Department of Agriculture, Animal and Plant Health Inspection Service 2012

1Plants have been found naturally infected, and P. ramorum has been cultured and/or detected using PCR, but Koch's postulates (formal proof of pathogenicity) have not been completed as of Feb 2012

2Riley and Chastagner 2011.