Association of Soil Moisture with Spread of Ceratocystis wageneri in Ponderosa Pine Disease Centers. D. S. Wilks, Former Research Associate, Department of Plant Pathology, University of California, Berkeley 94720. P. L. Gersper, Associate Professor, Department of Plant and Soil Biology, and F. W. Cobb, Jr., Professor, Department of Plant Pathology, University of California, Berkeley 94720. Plant Dis. 69:206-208. Accepted for publication 22 August 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-206.

Soil redox potentials, soil water potentials, and soil temperatures were measured at naturally occurring centers of black stain root disease, caused by Ceratocystis wageneri, in Pinus ponderosa in the central Sierra Nevada. Soil redox potentials were relatively high, probably because of low soil temperatures during periods of high soil moisture, and no relationship between redox potential and rate of disease spread was apparent. Soil water potentials, particularly in May, were strongly related to disease spread, indicating that disease spread in the field is favored on wetter sites.