Frequency and Pathogenicity of Fusarium spp. Associated with Seedling Diseases of Cotton in Louisiana. P. D. Colyer, Assistant Professor, Red River Research Station, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Bossier City 71113. . Plant Dis. 72:400-402. Accepted for publication 7 December 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0400.

Over a 2-yr period, Fusarium spp. were isolated from necrotic roots and hypocotyls of field-grown cotton seedlings at a frequency of 42%. Approximately 90% of the Fusarium spp. were identified as either F. solani or F. oxysporum. Other species isolated included F. equiseti, F. moniliforme, and F. graminearum. The different species and isolates within a species varied in virulence to cotton seedlings on the basis of pathogenicity tests conducted in the greenhouse. Few isolates caused postemergent damping-off, but many caused root and hypocotyl necrosis and / or death to the taproot. The F. solani isolates were more virulent than the other species.