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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGY, PATHOLOGY, AND EPIDEMIOLOGY OF EMERGING OOMYCETE PATHOGENS

Location: Foreign Disease-Weed Science

Title: Screening selected Gulf Coast forest species for susceptibility to Phytophthora ramorum

Authors
item Preuett, Jason -
item Collins, Daniel -
item Luster, Douglas
item Widmer, Timothy

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 2, 2013
Publication Date: July 30, 2013
Citation: Preuett, J.A., Collins, D.J., Luster, D.G., Widmer, T.L. 2013. Screening selected Gulf Coast forest species for susceptibility to Phytophthora ramorum. Plant Health Progress. PHP 2013-0730-01-RS.

Interpretive Summary: The pathogen that causes Sudden Oak Death is a threat to forests in the Gulf Coast region of the United States. However, very little is known about which native plants can be infected by the pathogen that causes this disease. It was found that Southern magnolia, sweetbay magnolia, yaupon, spicebush, baldcypress, and Virginia creeper can all be infected by the pathogen, while black willow and Eastern baccharis cannot. This research is important in that it provides more information on plants that can be infected by this pathogen and what might happen if this pathogen invades the Gulf Coast region. This will assist personnel in forestry and regulatory agencies (Forest Service and APHIS), who are impacted by this pathogen and can make strategic plans to help understand the spread and impact of this disease.

Technical Abstract: Phytophthora ramorum, the causal agent of sudden oak death in California oak woodlands, poses a threat to woody plants in the rest of the U.S., including the Gulf Coast area, which is regarded as a high risk location. Several plant species native to the Gulf Coast forest were tested for reaction to P. ramorum, including yaupon (Ilex vomitoria), spicebush (Lindera benzoin), Southern magnolia (Magnolia grandiflora), sweetbay magnolia (Magnolia virginiana), black willow (Salix nigra), baldcypress (Taxodium distichum), Virginia creeper (Parthenocissus quinquefolia), and Eastern baccharis (Baccharis halmifolia). 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 5.0, 0.2, 8.6, 1.5, 1.1, 0.2, 32.1, 4.9, and 27.9 percent for inoculated baldcypress, black willow, sweetbay magnolia, Virginia creeper (Louisiana), Virginia creeper (Maryland), Eastern baccharis, Southern magnolia, spicebush, and yaupon, respectively. Comparison of inoculated with 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). This is a first report of yaupon being an associated host of P. ramorum. The other species were not significantly different although infection was confirmed on baldcypress, spicebush, and Virginia creeper.

Last Modified: 12/19/2014
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