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Evaluation of Biological Seed Treatment for Controlling Root Diseases of Pea. Thor Kommedahl, Professor, Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108; Carol E. Windels, associate scientist, Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108. Phytopathology 68:1087-1095. Accepted for publication 15 December 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1087.

Of 100 bacteria and fungi isolated from roots and seeds of peas, and tested for antagonism to Fusarium solani and Rhizoctonia solani, 37 of 41 fungi and 22 of 59 bacteria proved antagonistic to one or both pathogens in culture. These 59 organisms were tested further against nine isolates of four root rot pathogens (Aphanomyces euteiches, Fusarium oxysporum, F. solani, and Rhizoctonia solani). They also were coated onto seeds and tested again in field soil in a rolled paper towel test, and in the greenhouse and field. Several organisms improved stand over no seed treatment. None of the laboratory or greenhouse screening tests predicted performance in the field, probably because of variation in weather and in pathogen activity during the 3 yr of field testing (1975-1977). Performance of one of the best fungal antagonists (Penicillium spp.) was enhanced by selection and by increase of inoculum on Czapek-Dox and malt agar media. In the greenhouse, P. oxalicum was as effective as captan and significantly better than no treatment, and in the field in 1977 it improved stand and pod number over no treatment.