Arsenate Herbicide Stress and Incidence of Summer Patch on Kentucky Bluegrass Turfs. R. W. Smiley, Associate Professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. M. Craven Fowler, Research Support Specialist, Department of Plant Pathology, Cornell University, Ithaca, NY 14853, and R. C. O’Knefski, Former Regional Turfgrass Specialist, Nassau County Cooperative Extension, Plainview, Long Island, NY. Plant Dis. 69:44-48. Accepted for publication 18 June 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-44.

Investigations were conducted on the relationships between arsenical weed control programs on Kentucky bluegrass and the incidence of summer patch (formerly known as Fusarium blight syndrome), caused by Phialophora graminicola. At locations where the disease is likely to occur, applications of calcium arsenate caused extreme amplifications of disease, enough to render it uncontrollable with fungicides. Where the disease is not known to occur, large excesses of arsenate failed to induce new occurrences of summer patch. These results are discussed in relation to soil moisture extremes known to predispose bluegrasses to the disease and to stresses caused by arsenicals in the root zones of plants.