Fusarium spp. from corn, sorghum, and soybean fields in the central and eastern United States

Samples of plant tissue and soil were collected from 41 corn, 18 sorghum, and 34 soybean fields in the central and southeastern United States in August 1986. Isolates of Fusarium were recovered from plant tissue, soil debris, and soil on a selective medium and identified to species. Fusarium spp. were recovered from all soils sampled. In corn, tissue usually was colonized with F. moniliforme, F. proliferatum, or F. subglutinans. F. semitectum, F. equiseti, F. oxysporum, F. graminearum, F. acuminatum, and F. chlamydosporum were recovered from debris but not from soil, and F. merismoides, F. proliferatum, and F. semitectum were recovered from soil but not from debris. In sorghum, F. moniliforme or F. proliferatum were present in 71% of the tissue samples and 18% of the debris samples. F. moniliforme was present in debris from 39% of the sorghum fields but was absent from the corresponding soil samples. F. acuminatum, F. chlamydosporum, and F. graminearum were found in debris but not in soil, and F. merismoides was found only in soil samples from sorghum fields. F. solani was present in either soil debris or soil from all sorghum fields, whereas F. oxysporum was found in debris at 44% of the sites and in soil at 72% of the sites. F. equiseti was found in both debris and soil at 33% of the sites. Fusarium spp. recovered from soybean tissue generally were different from those recovered from corn and sorghum tissue. F. oxysporum and F. solani were the predominant species and were present in 91 and 97% of the sites, respectively, whereas members of the Liseola section usually were absent. Soil and debris samples from the soybean fields contained F. acuminatum, F. equiseti, F. moniliforme, F. oxysporum, and F. solani. F. graminearum and F. semitectum were found in debris samples but not in soil samples, and F. chlamydosporum, F. compactum, F. merismoides, and F. proliferatum were found in soil samples but not in debris samples from soybean fields. F. anthophilum, F. avenaceum, and F. chlamydosporum were found in sites in southern states but not in northern states. All species found in northern states also were found in southern states, although differences in tissue, debris, and soil populations were observed. Soils of five different orders were sampled. All species were recovered from at least one Alfisol site, and all but F. avenaceum were recovered from at least one Ultisol site. F. oxysporum and F. solani were present in the soil and debris from more than 50% of the sites in each soil order, and members of Fusarium section Liseola could be found in plants at sites of each soil type. The distribution of Fusarium spp. observed in this study is consistent with the hypothesis that these fungi are widely distributed in host tissue under field conditions and that they respond to stress in the plant by taking advantage of preferential growth conditions to incite disease.