Plant diseases are influenced by environmental and fertility factors, and by topographical relief. Canola (cv. Hyola 401) and wheat (cv. Katepwa) were established on hummocky terrain near Prince Albert, Saskatchewan, to determine how diseases of these crops vary with nitrogen fertility and slope position, and to determine the interaction of fungicide application with these factors. Four nitrogen fertility rates (0, 40, 80, and 120 kg N/ha) were used for the main plots and each plot was split for foliar fungicide application (propiconazole in wheat and azoxystrobin in canola). At an upper and a lower slope position in each plot a 3 by 10 metre sample area was assessed for disease incidence/severity and yield. Leaf spots of wheat (septoria complex and tan spot) were observed to decrease in severity with increasing nitrogen fertility and with fungicide application over all slopes. Disease severity was greater on upper than on lower slopes. Yield of wheat was not affected by nitrogen fertility but was higher on lower slopes and with application of propiconazole. On both upper and lower slopes, the incidence of blackleg of canola increased with increasing nitrogen fertility and was reduced with azoxystrobin application. Blackleg incidence was higher on upper than on lower slopes. Yield of canola was not improved with application of nitrogen fertilizer or with fungicide, but was greater on lower slopes. Yields on upper slopes of both crops were likely reduced due to the dry conditions that occurred in the early growing season and at seed formation. Nitrogen fertility did not have an impact on yield of either crop possibly due to the warm winter that preceded the study causing increased nitrogen mineralization and availability. The lack of an interaction between nitrogen fertility, fungicide use or slope for disease severity or yield for either wheat and canola indicated that under the conditions of the study it was not beneficial to target inputs to specific slope positions.