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Development of Septoria nodorum Blotch on Winter Wheat Under Two Cultivation Schemes in Maryland. CHARLES E. ORTH, Former Graduate Student , Department of Botany, University of Maryland, College Park 20742-5815. ARVYDAS P. GRYBAUSKAS, Associate Professor, Department of Botany, University of Maryland, College Park 20742-5815. Plant Dis. 78:736-741. Accepted for publication 12 April 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0736.

Field experiments were conducted on soft red winter wheat cultivars Florida 302 and Coker 916 at three locations in Maryland over two seasons to assess the effect of cultivation schemes on Septoria nodorum blotch epidemics and the need for disease control. High-input cultivation (HIC) employed half the row spacing and 1.5-2 times the nitrogen fertility of conventional input cultivation. Subplots were inoculated with Stagono.tpora nodorum at different rates to develop various epidemic levels. Septoria nodorum blotch in the field was more severe on foliage but less severe on heads of Florida 302 than on Coker 916, regardless of the cultivation scheme. HIC tended to reduce disease severity and resulted in higher yields, regardless of cultivar. However, seed infection was either not affected or increased with HIC. Fungicides effectively improved only grain quality, regardless of the cultivation scheme employed. Greenhouse experiments were conducted to quantify the relative susceptibility of cultivars to Septoria nodorum blotch at three growth stages and to determine the effect of nitrogen fertility on disease development. High nitrogen fertility tended to suppress disease in the greenhouse trials. The reduction of Septoria nodorum blotch severity on foliage by HIC in the field was apparently due to interference of splash dispersal of spores in the denser canopy and the suppressive effect of high nitrogen fertility.