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A Method of Evaluating Postemergence Damping-Off Pathogens of Bedding Plants. Christine Taylor Stephens, Research associate, Department of Plant Pathology, The Ohio State University, Columbus 43210, Present address of senior author: Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; C. C. Powell(2), and A. F. Schmitthenner(3). (2)(3)Associate professor, and professor, respectively, Department of Plant Pathology, The Ohio State University, Columbus 43210, and the Ohio Agricultural Research and Development Center, Wooster 44691. Phytopathology 71:1225-1228. Accepted for publication 13 March 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1225.

An inoculation method was developed to allow rapid assay examination of the pathogenicity of numerous fungal isolates inducing damping-off on many plant types. Seeds of host plants were thickly sown in rows in pots containing a moistened peat-vermiculite mix. Inoculum as a 12 12-mm agar disk removed from a petri plate culture of the fungus, was buried at the end of the seedling row at seedling emergence. The pots were placed in plastic bags and incubated on a shaded greenhouse bench at 26 2 C. After 9 days, the length of seedling row in which damping-off occurred was measured. This method maximized the amount of damping-off, minimized variability among replicates, and adequately revealed pathogenic isolates and susceptible hosts. Furthermore, the test conditions closely approximate seedling germination and early growth conditions prevalent in Ohio greenhouses.

Additional keywords: soil microbiology, Pythium, Rhizoctonia.