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Screening Selected Gulf Coast and Southeastern Forest Species for Susceptibility to Phytophthora ramorum

Jason A. Preuett, Daniel J. Collins, Douglas Luster, Timothy L. Widmer
Plant health progress 2013 v.14 no.1 pp. -
Baccharis halimifolia, Ilex vomitoria, Lindera benzoin, Magnolia grandiflora, Magnolia virginiana, Parthenocissus quinquefolia, Phytophthora ramorum, Quercus, Salix nigra, Taxodium distichum, death, forests, fungal diseases of plants, hosts, indigenous species, leaf area, leaves, necrosis, screening, tree diseases, woody plants, zoospores, Louisiana, Maryland
Phytophthora ramorum, the causal agent of sudden oak death, poses a threat to woody plants in the rest of the United States. Several plant species native to Gulf Coast and southeastern US forests were tested for reaction to P. ramorum, including eastern baccharis (Baccharis halmifolia), spicebush (Lindera benzoin), yaupon (Ilex vomitoria), southern magnolia (Magnolia grandiflora), sweetbay magnolia (M. virginiana), Virginia creeper (Parthenocissus quinquefolia), black willow (Salix nigra), and baldcypress (Taxodium distichum). The foliage of each species was inoculated with a zoospore suspension and placed in a dew chamber for 5 days. The average percentage of leaf area necrosis was 0.2, 4.9, 27.9, 32.1, 8.6, 1.5, 1.1, 0.2, and 5.0% for inoculated eastern baccharis, spicebush, yaupon, southern magnolia, sweetbay magnolia, Virginia creeper (Louisiana), Virginia creeper (Maryland), black willow, and baldcypress, respectively. Comparison of the percent necrotic leaf area between inoculated and non-inoculated plants showed significant differences (P ≤ 0.05) for yaupon (P = 0.0008), southern magnolia (P = 0.001), and sweetbay magnolia (P = 0.0009). The other species did not show significant differences although infection was confirmed on spicebush, Virginia creeper, and baldcypress. This is a first report of yaupon, sweetbay magnolia, and baldcypress being hosts of P. ramorum.