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Effects of Chloride Fertilizer and Systemic Fungicide Seed Treatments on Common Root Rot of Barley. P. A. Shefelbine, Former Graduate Student, Department of Plant Pathology, Montana State University, Bozeman 59717. D. E. Mathre, Professor, Department of Plant Pathology, Montana State University, Bozeman 59717, and G. Carlson, Agronomist, Northern Agricultural Research Center, Havre, MT 59270. Plant Dis. 70:639-642. Accepted for publication 2 February 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-639.

Two chloride fertilizers and six systemic fungicides, which inhibit ergosterol biosynthesis, were tested for efficacy in controlling Cochliobolus sativus of spring barley in Montana in 1981 and 1982. Nuarimol and imazalil seed treatments increased emergence compared with that observed in uninoculated plots, whereas chloride fertilizers had no effect on plant emergence. Common root rot (CRR) was controlled only with fertilizers containing chloride, indicating that the chloride anion was the probable effective agent. Although most of the fungicides reduced disease ratings, only nuarimol was statistically significant in disease reduction. Significant disease control effected by chloride or nuarimol use did not increase grain yield. Overall, the results suggest that healthy plants in a diseased plant population may compensate for stand reduction by an increase in other yield components. These results would render apparent disease control economically unfeasible under conditions of mild or moderate CRR disease.

Keyword(s): Helminthosporium sativum.