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Disease Note

First Report of Gray Leaf Spot (Cercospora zeae-maydis) of Corn in Delaware. J. A. Hawk and R. B. Carroll, Department of Plant Science, University of Delaware, Newark 19717-1303, and F. M. Latterell, Plant Disease Research Laboratory, USDA-ARS, Frederick, MD 21701. Plant Disease 69:361, 1985. Accepted for publication 4 January 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-361e.

Mature lesions of gray leaf spot were observed during the dough stage (late August 1984) in commercial corn-hybrid test fields and growers' fields near Little Creek and Middletown, Delaware.  Gray leaf spot has been previously reported in Maryland, Pennsylvania, and Virginia.  The Little Creek field was no-till after soybeans and nonirrigated, whereas the Middletown field was chisel-plowed and disked, had been in continuous corn production for several years, and was irrigated with a center-pivot system.  Rainfall was above average throughout the growing season.  The disease was more extensive at Little Creek, with some leaves at midplant showing over 75% lesion coverage by late September.  This field was characterized by poor air drainage and proximity to Delaware Bay and marshlands.  Isolates of Cercospora zeae-maydis Tehon & Daniels have been cultured and identified from diseased leaves at both locations.

References: Latterell, F. M., and Rossi, A. E. Plant Dis 67:842, 1983.