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Colonization Patterns of Verticicladiella procera in Scots and Eastern White Pine and Associated Resin-Soaking, Reduced Sapwood Moisture Content, and Reduced Needle Water Potential. W. Elliott Horner, Graduate research assistant, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute & State University, Blacksburg 24061, Present address: Tulane Medical Center, 1500 Perdido St., New Orleans, LA 70112; S. A. Alexander(2), and Kathy J. Lewis(3). (2)(3)Associate professor, and graduate research assistant, respectively, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute & State University, Blacksburg 24061, (3)Present address: Ministry of Forests, Pest Management Division, Prince George, BC, Canada. Phytopathology 77:557-560. Accepted for publication 4 September 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-557.

The colonization pattern of Verticicladiella procera in diseased pines was studied by plating tissue onto both general and selective media. A systematic sampling procedure was repeated on 10 Pinus sylvestris and 10 P. strobus Christmas trees (59 yr old) with symptoms of Procera root disease. Sampling points were at predetermined positions up the stem (four points on each of two or four sides), around the root collar (eight points), and along each root. Relative recovery frequencies of the fungus were, in decreasing order, root collars, roots, and stems. Root collar recoveries were distributed uniformly around the root collar. Recovery frequency along roots declined rapidly acropetally and fit a negative exponential distribution. Recovery of V. procera from bark was significantly more frequent than from wood. This recovery pattern suggests that colonization by V. procera involves initial establishment in bark at the root collar with subsequent acropetal development. The status of symptomatic trees was further characterized and shown to include needle water potentials lower than controls, low sapwood moisture content, and appreciable amounts of resin-soaked tissue in the stem cross-section.