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Relation of Soil Redox Potential to Infection of Ponderosa Pine by Ceratocystis wageneri. D. S. Wilks, Former research associate, Department of Plant Pathology, Present address: Department of Atmospheric Sciences, Oregon State University, Corvallis 97331; P. L. Gersper(2), and F. W. Cobb, Jr.(3). (2)Associate professor, Department of Plant and Soil Biology, University of California, Berkeley 94720; (3)Professor, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 73:1120-1125. Accepted for publication 16 February 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1120.

Influences of soil aeration and associated properties, as reflected by soil redox potential, on infection and colonization of inoculated ponderosa pine seedlings by Ceratocystis wageneri were studied under controlled conditions in the greenhouse. Two field soils with markedly different structures yielded differing infection percentages under established moisture regimes. When the two soils were mixed in varying proportions, a range of soil aeration and redox potential conditions was produced under a single moisture regime. Disease severity was greatest under conditions of restricted (intermediate redox potentials) but not completely impeded aeration (very low redox potentials). In the more strongly reduced soils, colonization by the fungus down the taproots of infected seedlings generally extended to the depth at which calculated gas-phase oxygen levels were continuously at or near zero. Implications for spread of field disease centers are discussed.

Additional keywords: black-stain root disease, soil manganese, Verticicladiella wageneri.