Knowledge is limited about the impact of foliar diseases on wheat yield in Wisconsin. The objective of this study was to compare yield and diseases of wheat cultivars in several locations in Wisconsin in 2009 and 2010. Thirty-six wheat cultivars were planted in a randomized complete block design at field sites near Arlington, Chilton, and Lancaster, WI. At a fourth location, Janesville, WI, the design was a split plot with foliar fungicide application at Zadoks growth stage (GS) 45 at the whole-plot level and cultivar at the subplot level. Disease assessments were made four times during the growing season for powdery mildew (PM), Septoria/Stagonospora leaf blotch (SLB), and leaf rust. Incidence and severity of Fusarium head blight were assessed on 100 heads per plot at GS 85. Linear mixed-model analyses were used to study the effects of location, cultivar, and disease on grain yield (α = 0.05). Overall, SLB and PM were the most prevalent diseases. SLB severity was uniform among locations and PM was most prevalent at Arlington and Chilton. In both years, yield was affected by location, cultivar, location–cultivar interaction, and location–SLB and location–PM interactions. Yield was also negatively affected by PM in 2010. No effect of fungicide on disease severity or yield was observed at Janesville in either year. These results suggest that cultivar selection and location strongly influence grain yield in Wisconsin and that powdery mildew is capable of reducing grain yield.
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