Calcium Silicate Suppresses Powdery Mildew and Increases Yield of Field Grown Wheat

During three consecutive years of field trials conducted in northwestern New Jersey on a Quakertown silt loam soil (fine–loamy, mixed, active, mesic Typic Hapludult), a calcium silicate, steel slag by-product (CSS), was added as an effective liming agent to long winter wheat (Triticum aestivum L.) and evaluated for its suppressive effects on powdery mildew disease (Erysiphe graminis DC. f. sp. tritici Em. Marchal Blumeria graminis (DC.) E.O. Speer = E. graminis DC. Oidium monilioides (Nees) Link [anamorph]). Limestone was used as the control in a completely random design, consistent for treatment during all trial years. Plots were split for one fungicide, propiconazole (1-[[2(2,4-Dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]1-H-1,2,4-triazole), application per year. The field was allowed to become naturally inoculated. In 2006 disease symptoms did not appear until late in the season. Although no significant grain yield response was exhibited in 2006, powdery mildew lesions were reduced by 29% on the flag leaves of wheat plants in the CSS treated plots. In 2007, powdery mildew was not diagnosed, but non-pathogenic Alternaria spp. leaf blotch was observed late season. Leaf blotch lesions were reduced 25% on flag leaves in the CSS-treated plots. During 2008, powdery mildew lesions on flag leaves were 44% less and yields were 10% greater in plots treated with CSS. Our results suggest that the use of CSS as an effective neutralizer of soil acidity may have the added benefit of suppressing powdery mildew in field grown winter wheat.