Mycelial Development and Control of Phomopsis sojae in Artificially Inoculated Soybean Stems. H. C. Hill, Graduate Research Assistant, Department of Plant Pathology and Crop Physiology, Louisiana State University, Agricultural Experiment Station, Baton Rouge 70803. N. L. Horn, Professor, Department of Plant Pathology and Crop Physiology; and W. L. Steffens, Research Associate, Department of Zoology and Physiology, and Graduate Student, Department of Plant Pathology and Crop Physiology, Louisiana State University, Agricultural Experiment Station, Baton Rouge 70803. Plant Dis. 65:132-134. . Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-132.

The direction and rate of mycelial growth of Phomopsis sojae were traced from a single inoculation site in greenhouse-grown soybean (Glycine max cv. Davis) plants. Serial stem sections from inoculated plants were plated on potato-dextrose agar (PDA) and observed with a scanning electron microscope. Mycelium remained within 2 cm of the point of inoculation until senescence began. The pathogen grew terminally approximately 5.5 cm by the late R8 stage of growth. In another greenhouse test, soybean plants in the V3 growth stage were inoculated with a conidial suspension of P. sojae 24 hr before, at the time of, and 7, 10, 14, 17, and 21 days after a foliar application of benomyl at 0.3 g/L. Growth of P. sojae was detected on PDA only from stem sections inoculated 21 days after the fungicide treatment.