Fungi Associated with Soybean Seedling Disease in Iowa. S. S.A. Rizvi, former Postdoctoral Research Associate, Department of Plant Pathology, Iowa State University, Ames 50011. X. B. Yang. Plant Dis. 80:57-60. Accepted for publication 6 October 1995. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0057.

Surveys were conducted over a 2-year period to identify fungi associated with soybean seedling disease in Iowa. Fungi were isolated from diseased soybean seedlings collected from 52 and 66 locations in 1993 and 1994, respectively. The percentages of major fungal taxa isolated from soybean seedlings in the 2 years were Rhizoctonia solani, 27.5% in 1993 and 27.3% in 1994; Fusarium spp., 11.9% in 1993 and 13.7% in 1994; and Pythium spp. and Phytophlhora sojae, cumulatively 60.5% in 1993, and 31.7% and 24.3% in 1994 respectively. Other isolated fungi were the seed decay pathogen Phomopsis longicolla, and the nonpathogenic Rhizopus stolonifer and Trichoderma viride. Species of Fusarium and Pythium were identified as F. acuminatum, F. equiseti, F. oxysporum, P. aphanidermatum, P. irregulare, P. myriotylum, P. sylvaticum, P. ultimum var. sporangiiferum, and P. ultimum var. ultimum. Repeated tests of pathogenicity confirmed that Pythium spp., Phylophthora sojae, and R. solani were the major causal fungi associated with the seedling disease complex of soybeans in Iowa.