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Longevity of Ceratocystis fagacearum in Ammate Treated and Nontreated Root Systems. J. M. Skelly, Formerly Research Assistant, Department of Plant Pathology, Pennsylvania State University, Present address: Associate Professor Plant Pathology, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061; F. A. Wood, Professor of Plant Pathology, Department of Plant Pathology, Pennsylvania State University Present address: Head, Department of Plant Pathology, University of Minnesota, St. Paul 55108. Phytopathology 64:1483-1485. Accepted for publication 12 June 1974. DOI: 10.1094/Phyto-64-1483.

Two roots were removed from each of 292 wilt-killed oaks during 1965 and isolations were made using Barnett’s medium. During 1966 and 1967, two roots from each of 49 Ammate-treated stumps were treated similarly. Ceratocystis fagacearum was isolated from 23 of 45, 21 of 101, 1 of 50, 2 of 64, and 0 of 30 of the nontreated trees dead 1 to 5 years, respectively. The fungus was obtained from 17% (4 of 24) of the trees treated with Ammate 1 yr before sampling and from none of those trees treated 2 yr before sampling (0 of 25). Roots remained solid for 2 yr after tree death, but then rapidly deteriorated. These data indicate that the control methods used in Pennsylvania reduce the amount of inoculum available for spread by root grafts or by root inhabiting insects.