Calcium Silicate Suppresses Disease Leaf Lesions on Wheat when Applied as a Liming Agent.

ABSTRACT Powdery mildew, caused by the fungal pathogen (Blumeria graminis DC. f. sp. tritici Speer) can cause substantial yield losses in wheat (Triticum aestivum L.) by affecting grain fill and reducing test weight. Economic losses vary depending on current market price, but at yield losses greater than 10%, fungicides are generally recommended. In field trials conducted on a Quakertown silt loam soil in northwestern New Jersey in 2006, 2007 and 2008, calcium silicate (Si) was added as an alternative liming material to long winter wheat and evaluated for powdery mildew disease suppression. Calcium carbonate was used as a control and the plots were split with half of each plot receiving one propiconazole fungicide application. The field was allowed to become naturally inoculated. Due to dry weather conditions in the spring of 2006, the pathogen arrived later in the season than expected. Although a significant grain yield response was not exhibited in the first trial year, powdery mildew lesions were reduced by 29% on the flag leaves of wheat plants in the silicate amended plots. Flag leaf tissue analysis showed that wheat grown in calcium silicate amended plots had a mean Si content of 10.3g/kg Si compared with 8.0g/kg Si in the control plots. In 2007, the same amendments were applied with rates determined by lime requirement index, for a target pH of 6.5. Although, Powdery mildew was not observed throughout the growing season, Alternaria spp. Leaf blotch was observed later in the season. Leaf blotch lesions were reduced 16% on Si treated flag leaves when compared with the calcium carbonate controls. The experiment is being continued in 2008. From our preliminary results, it is suggested that the use of calcium silicate as a lime substitute may have the added benefit of suppressing powdery mildew in field grown winter wheat.