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Biological Control of Fusarium Crown Rot of Tomato Under Field Conditions. J. J. Marois, Graduate research assistant, Department of Plant Pathology, University of Florida, Gainesville 32611, Present address of senior author: Soilborne Diseases Laboratory, Plant Protection Institute, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Beltsville, MD 20705; D. J. Mitchell(2), and R. M. Sonoda(3). (2)Professor, Department of Plant Pathology, University of Florida, Gainesville 32611; (3)Professor, IFAS Agricultural Research Center, University of Florida, P.O. Box 248, Ft. Pierce 33450. Phytopathology 71:1257-1260. Accepted for publication 10 April 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1257.

Conidial suspensions of five fungal antagonists of Fusarium oxysporum f. sp. radicis-lycopersici were applied to the roots and crowns of tomato transplants at the time of planting. The suspension contained 5 105 conidia of each of three isolates of Trichoderma harzianum, one isolate of Aspergillus ochraceus, and one isolate of Penicillium funiculosum. The pathogen was added at the time of planting to soil 10 cm from the transplant as 0, 50, 500, and 5,000 chlamydospores per plant in 20 ml of water. The incidence of disease increased as the inoculum density of the pathogen was increased in fumigated soil not augmented with the antagonists; disease incidence, however, did not increase as the inoculum density was increased in fumigated soils that were augmented with the antagonists. At 5,000 chlamydospores of the pathogen per plant, disease incidence at harvest was 7% in soils augmented with antagonists and 37% in nonaugmented soils. The pathogen population decreased from 600 to 200 propagules per gram in soil augmented with antagonists, but increased from 1,000 to over 5 104 propagules per gram in nonaugmented soils. Yield was not affected significantly by treatment or planting date.