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Effect of Atrazine on Growth of Fusarium oxysporum f. sp. vasinfectum. R. Rodriguez- Kabana, Assistant Professor, Auburn University Agricultural Experiment Station, Auburn, Alabama 36830; E. A. Curl, Professor of Plant Pathology, Auburn University Agricultural Experiment Station, Auburn, Alabama 36830. Phytopathology 60:65-69. Accepted for publication 28 July 1969. DOI: 10.1094/Phyto-60-65.

Effect of atrazine (2-chloro-4-ethylamino-6-iso-propylamino-s-triazine) on growth of Fusarium oxysporum f. sp. vasinfectum was studied in Czapek’s liquid medium and in sterilized soil containing 0, 8, 20, 40, and 80 µg of active herbicide per ml of medium or per g of soil. In liquid culture, exposure of the fungus to 40 or 80 µg atrazine retarded mycelial growth during the first 6 days of incubation, but not thereafter. Conductivity values and concentrations of nutrients in the medium were inversely proportional to mycelial growth. The ratio values for amount of mycelium produced to nutrients utilized, calculated 6 days after inoculation, were lowest for the two highest herbicide treatments. Production of CO2-carbon increased significantly in soil cultures of the fungus with atrazine concentrations of 20, 40, and 80 µg/g. This stimulation was first evident after 6 days’ incubation, and remained so until the last sampling at 14 days. Also, the ratios of amount of carbon evolved to nitrate-nitrogen consumed were significantly higher for the three highest herbicide treatments at the last sampling.