Planting Date and Nitrogen Effects on Fusarium Head Blight and Leaf Spotting Diseases in Spring Wheat

Cultural management practices play important roles in minimizing losses caused by Fusarium head blight (FHB) and leaf spotting diseases (leaf-spot) in wheat (Triticum aestivum L.). A field experiment was conducted in Ottawa, Canada, for 3 yr (2003-2005) in two sites representing clay loam and sandy loam soils to examine the effects of planting date and N management on the incidence and severity of FHB and leaf-spot {tan spot, Septoria leaf blotch and Stagonospora nodorum blotch) in spring wheat. The cultivar AC Brio was seeded at three dates at approximately 10-d intervals starting in the last week of April. The five N treatments included 0, 60, and 100 kg N ha^-1 applied as starter; 60 + 40 kg N ha^-1 (starter + top-dress at boot stage); and 60 + 40 kg N ha^-1 (starter + foliar spray at boot stage). Generally, incidence of FHB and severity of leaf-spot were greater in the heavy-textured soil than in the light-textured soil. Across site-year, the incidence of FHB ranged from 13 to 45%, and severity varied from 14 and 52%. On both soils, planting date had a consistently greater effect on the incidence and severity of FHB: the later the planting date beyond 9 May, the greater the incidence of FHB. The late-planted wheat also had the greatest severity of leaf-spot. Planting after 9 May also significantly reduced grain yield by 15 to 45%. Wheat grown without added N had the greatest incidence of FHB and leaf-spot severities than that supplied with adequate N, especially in the heavy-textured soil. The effect of N on FHB was not consistent over site-years, but leaf-spot was significantly reduced with a starter application of N at 100 kg ha^-1. Our data indicate that environmental variation induced by different planting dates or by different growing seasons and site appeared to have greater effects on FHB and leaf-spot in wheat than N application. The results suggest that the incidence of FHB and severity of leaf-spot in spring wheat can be minimized through early planting combined with adequate starter N application.