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Ecology and Epidemiology

Effect of Interaction Between Fusarium, Pythium, and Rhizoctonia on Severity of Bean Root Rot. D. J. Pieczarka, Graduate Research Assistant, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456; G. S. Abawi, Assistant Professor, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456. Phytopathology 68:403-408. Accepted for publication 25 August 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-403.

The effect of Fusarium solani f. sp. phaseoli, Pythium ultimum, and Rhizoctonia solani singly and in combination on beans was studied in artificially-infested, pasteurized, bean-field soil in a controlled environment. Root rot was more severe in soil infested with both P. ultimum and F. solani f. sp. phaseoli. Data suggest that a synergistic relationship exists between these pathogens. Root-rot ratings of plants growing in soil infested with P. ultimum, F. solani f. sp. phaseoli, or a combination of the two organisms was 3.2, 0.8, and 5.1, respectively. Similarly, reduction in total dry weight per plant was 52, 12, and 74%, respectively. No interaction was observed between R. solani and F. solani f. sp. phaseoli. However, R. solani significantly reduced the severity of root rot incited by P. ultimum when the two were combined, suggesting an antagonistic relationship. Observations in recent years suggest that the synergistic interaction between P. ultimum and F. solani f. sp. phaseoli occurs under field conditions in New York, particularly during cool, wet periods.

Additional keywords: Phaseolus vulgaris.