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Etiology

Edaphic Parameters Associated with Shore Juniper Decline. Deborah R. Fravel, Former graduate teaching assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650, Current address: Soilborne Diseases Laboratory, Plant Protection Institute, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705; D. M. Benson(2), and R. I. Bruck(3). (2)(3)Associate professor, and assistant professor, respectively, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Phytopathology 73:204-207. Accepted for publication 28 July 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-204.

In the absence of evidence of a biotic agent as the primary cause of decline of shore juniper (Juniperus conferta), abiotic factors were examined to determine their roles in contributing to decline. Six of 20 edaphic components measured in 20 landscape plantings were significantly interrelated to decline index in a multivariate principal axis factor analysis. These parameters were calcium, clay + silt content, magnesium, nitrate, phosphorus, and zinc. Where soil horizons could be distinguished, parameters of the A+B horizon were better indicators of decline than those of the C horizon. Supportive evidence for the involvement of these components was provided by tissue nutrient analysis from landscape plantings and from greenhouse studies of nutrient deficiencies and water stress in which nitrogen deficiency and, in one case, both water excesses and deficiencies, induced symptoms resembling decline.