Amelioration of Tan Spot-Infected Wheat with Nitrogen. D. M. Huber, Professor, Botany and Plant Pathology Department, Purdue University, West Lafayette, IN 47907. T. S. Lee, M. A. Ross, and T. S. Abney. Former Postdoctoral Research Assistant, Professor, and USDA-ARS Plant Pathologist, Botany and Plant Pathology Department, Purdue University, West Lafayette, IN 47907. Plant Dis. 71:49-50. Accepted for publication 18 September 1986. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987. DOI: 10.1094/PD-71-0049.

Effects of nitrogen rate and form (0, 55, 110 kg/ha with and without nitrapyrin) on severity of tan spot of winter wheat were evaluated in southern Indiana. The Ryker silt loam soil was conventionally tilled, and wheat cultivars Auburn, Caldwell, and Blazer (resistant, moderately susceptible, and susceptible, respectively, to Pyrenophora tritici-repentis) were planted in a randomized, complete block design field experiment. Nitrapyrin inhibited nitrification, prevented overwinter loss of nitrogen, and increased the proportion of ammonium nitrogen taken up by the plants. The severity of tan spot decreased and yields increased as the rate of nitrogen increased. Disease severity was reduced further by inhibiting nitrification. The number of infection loci was similar in all treatments; however, the rate of lesion development was markedly reduced as the nitrogen rate increased, and the pinpoint lesions developing on Blazer at the highest rate of stabilized nitrogen were similar to those on the resistant Auburn. This research indicates that both the rate and form of nitrogen influence the severity of tan spot of winter wheat and that nitrogen management may provide a cultural control of this disease.

Keyword(s): integrated pest management, nitrogen stabilization.