Yields of Onion Cultivars in Midwestern Organic Soils Infested with Fusarium oxysporum f. sp. cepae and Pyrenochaeta terrestris. Melvyn L. Lacy, Professor, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. David L. Roberts, Graduate Research Assistant, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Plant Dis. 66:1003-1006. Accepted for publication 2 March 1982. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-1003.

Long-day, yellow-skinned onion (Allium cepa) cultivars and experimental hybrids were evaluated for yield response in a field experiment on muck soils naturally or artificially infested with Fusarium oxysporum f. sp. cepae or Pyrenochaeta terrestris or both. Infestation with Pyrenochaeta significantly reduced numbers of plants but not weights of bulbs; infestation with Fusarium significantly reduced both numbers of plants and weights of bulbs per hectare. There was a significant interaction of Fusarium × cultivar (P = 0.01) and of Fusarium × Pyrenochaeta × cultivar (P = 0.05) but not of P. terrestris × cultivar. Across the entire experiment, the cultivars XPH 419, Inca, XPH 70, Epoch, and MSU 8155 × 826 were in the highest yield range. Some cultivars not in this group yielded well in Pyrenochaeta-infested soil but not in Fusarium-infested soil. Overall, Fusarium reduced yields and stands more than Pyrenochaeta.

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