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Disease Detection and Losses

Use of Paraquat to Aid Detection of Fungi in Soybean Tissues. R. F. Cerkauskas, Graduate research assistant, Department of Plant Pathology, University of Illinois, Urbana 61801; J. B. Sinclair, professor, Department of Plant Pathology, University of Illinois, Urbana 61801. Phytopathology 70:1036-1038. Accepted for publication 1 May 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-1036.

Soybean stems and pods were surface disinfested, then immersed in a solution of commercial paraquat and incubated for 4 days under continuous light at 25 C. A greater number of lesions with fruiting structures and conidia of Phomopsis spp., Cercospora kikuchii, and Fusarium spp. were formed on plant parts immersed in paraquat than on nonimmersed tissues. There was no increase in the occurrence of Alternaria spp. Nontreated plant parts incubated for an additional 6 days failed to develop lesions in numbers equal to those of the paraquat-treated tissues. Field application of paraquat resulted in greater numbers of pycnidia of Phomopsis spp. and acervuli of Colletotrichum dematium var. truncata on stems of Bonus and Wells soybeans than on nonsprayed plants.

Additional keywords: pod and stem blight, purple seed stain, Diaporthe phaseolorum var. sojae, Glycine max, herbicides.