EFFECTS OF TILLAGE, ROW WIDTH, AND CULTIVAR ON FOLIAR DISEASES OF DOUBLE-CROP SOYBEAN

Experiments were conducted over two years, 1985 and 1986, to determine the effect of tillage systems, row widths, and soybean cultivars on f oliar diseases in double-crop soybean. The soybean cultivars Pershing, susceptible to bacterial blight, and Avery, resistant to bacterial bl ight, were each planted in 38-cm and 75-cm row widths in soil under co nventional tillage or no-tillage following winter wheat. There was a s ignificant interaction (P = 0.0001) between tillage and cultivar for t he severity of bacterial blight and a significant interaction (P = 0.0 01) for tillage, cultivar, and year for the severity of brown spot. Ti llage did not influence bacterial blight severity on Avery; however, d isease severity was higher on Pershing soybean in tilled plots. Genera lly, brown spot severity was higher in 1986 than in 1985, lower on Ave ry than Pershing in both years, and higher in tilled than no-tilled co nditions. Row width did not affect the severity of these diseases.