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Sources of Species of Fusarium in Northern Hardwood Forests. T. Craig Weidensaul, Head, Laboratory for Environmental Studies, and Assistant Professor of Plant Pathology, Ohio Agricultural Research and Development Center, Wooster, Ohio 44691; Francis A. Wood, Research Associate, Center for Air Environment Studies, and Professor, Department of Plant Pathology, The Pennsylvania State University, University Park, Pennsylvania 16802. Phytopathology 63:367-371. Accepted for publication 9 September 1972. DOI: 10.1094/Phyto-63-367.

Several species of Fusarium, capable of causing Fusarium canker of sugar maple, were found in the soil and air in forest stands and in bark of healthy maple trees. Air samples were collected in Pennsylvania sugar maple stands under various weather conditions between April and November. Soil and bark samples were collected in the same stands. Two isolates each of Fusarium solani and F. roseum, and three of F. tricinctum, were collected from 25,000 ft³ of air sampled. One hundred-eleven isolates of Fusarium were obtained from forest soil and maple bark. Sixty, 26, 15, and one of the isolates recovered were F. solani, F. roseum, F. tricinctum, and F. rigidiusculum, respectively. Thirty-two of the F. solani isolates and the one isolate of F. roseum from soil caused cankers on one or more of eight inoculations. Sixteen, 11, 12, and one of the bark isolates of F. solani, F. roseum, F. tricinictum, and F. rigidiusculum, respectively, caused cankers. In addition, all three isolates of F. tricinctum and one isolate of F. roseum recovered from air caused cankers. All pathogenic species of Fusarium were obtained from bark at 5.5 m or less aboveground. There was no apparent association between isolate pathogenicity and the tree face from which it was isolated. More pathogenic isolates were recovered from stands with moderately and severely cankered trees than from stands with trees only slightly affected.