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Prevalence and Pathogenicity to Corn of Fusarium species from Corn Roots, Rhizosphere, Residues, and Soil. H. L. Warren, Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907; Thor Kommedahl, Department of Plant Pathology, University of Minnesota, St. Paul 55101. Phytopathology 63:1288-1290. Accepted for publication 11 April 1973. DOI: 10.1094/Phyto-63-1288.

Among species of Fusarium isolated from corn roots, plant residues, rhizosphere, and soil, in plots where corn had been grown annually for 10 years, F. oxysporum, F. solani, and F. roseum predominated, making up 62, 21, and 12%, respectively, of the colonies of Fusarium species isolated. Other species of Fusarium (F. moniliforme, F. tricinctum, and F. episphaeria) totaled 4% of the colonies of Fusarium isolated. In soil where fertilizers were applied and plant residues were removed, F. roseum was more numerous in the rhizosphere than in nearby soil, but where fertilizers were applied and plant residues were present, it was more numerous in nearby soil than in the rhizosphere. If roots were wounded, F. oxysporum in field soil significantly reduced dry weight of plants over nonwounded roots at 18, 24, and 29 C, but greater losses were sustained at the higher temperature. F. roseum reduced dry weight of plants at 18 and 24 C but not at 29 C. Both species, mixed in soil, reduced dry weight of plants at all three temperatures.