Relationship Between Phoma macdonaldii and Premature Death of Sunflower in North Dakota. P. A. Donald, Former Graduate Research Assistant, USDA ARS, Department of Plant Pathology, North Dakota State University, Fargo 58105. J. R. Venette, and T. J. Gulya. Associate Professor, and Adjunct Professor, USDA ARS, Department of Plant Pathology, North Dakota State University, Fargo 58105. Plant Dis. 71:466-468. Accepted for publication 6 February 1987. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987. DOI: 10.1094/PD-71-0466.

Isolations from prematurely dead field-grown sunflowers yielded six potentially pathogenic fungal genera. Phoma macdonaldii was the single most commonly isolated organism from these plants. Koch’s postulates were completed in the greenhouse with two isolates of P. macdonaldii. Evaluation of 370 field-grown plants showed a perfect association between presence of girdling lesions on naturally infected plants and 185 plants with premature death. P. macdonaldii was isolated from the girdling lesions.