APS Abstracts of Presentations
Log inoculations to assess tree susceptibility to sudden oak death. E. M. HANSEN and W. Sutton. Dept. Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331. Phytopathology 92:S33. Publication no. P-2002-0237-AMA. Phytophthora ramorum, agent of sudden oak death, causes girdling cankers on tanoak (Lithocarpus densiflorus) in Oregon. As a test of potential host range, we inoculated freshly cut logs, 10-20 cm dia. and about 1 m long, of native conifer and angiosperm tree species. Plugs of bark (5 mm dia.) were removed to the cambium, and a matching plug of colonized agar (or sterile agar) was inserted, then covered by wet gauze and foil. Bark was stripped after 5 weeks and extent of phloem necrosis was measured. Isolations were made from canker margins. Necrotic area was greatest on tanoak and Port-Orford-cedar. Smaller lesions developed on California black oak, Oregon white oak, chinquapin, and canyon live oak. Average lesion areas were at least 10 times greater on tanoak than on the Quercus species tested. Lesion breadth on tanoak was nearly as great as lesion length, but lesions were much narrower on other hosts. Lesion extent depended on time of year that logs were collected. Other hardwoods and conifers did not support expanding lesions. P. ramorum was regularly reisolated from lesion margins. Four P. ramorum isolates tested did not differ significantly in lesion area.
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