DEVELOPMENT OF SEPTORIA-NODORUM BLOTCH ON WINTER-WHEAT UNDER 2 CULTIVATION SCHEMES IN MARYLAND

Field experiments were conducted on soft red winter wheat cultivars Fl orida 302 and Coker 916 at three locations in Maryland over two season s to assess the effect of cultivation schemes on Septoria nodorum blot ch epidemics and the need for disease control. High-input cultivation (HIC) employed half the row spacing and 1.5-2 times the nitrogen ferti lity of conventional input cultivation. Subplots were inoculated with Stagonospora nodorum at different rates to develop various epidemic le vels. 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 r esulted in higher yields, regardless of cultivar. However, seed infect ion was either not affected or increased with HIC. Fungicides effectiv ely improved only grain quality, regardless of the cultivation scheme employed. Greenhouse experiments were conducted to quantify the relati ve susceptibility of cultivars to Septoria nodorum blotch at three gro wth stages and to determine the effect of nitrogen fertility on diseas e development. High nitrogen fertility tended to suppress disease in t he greenhouse trials. The reduction of Septoria nodorum blotch severit y on foliage by HIC in the field was apparently due to interference of splash dispersal of spores in the denser canopy and the suppressive e ffect of high nitrogen fertility.