Powdery Mildew Development is Highly Associated with a Combination of Sowing Date, Weather, Wheat Cultivar, and Maturity

Following favourable agro-ecological conditions, powdery mildew becomes a destructive disease in wheat worldwide. Efficiency of the most common control methods (fungicide application and plant resistance) for wheat powdery mildew improves by using a better understanding of the effects of highly influential agronomic practices and weather factors on disease development. Disease severity was rated at plot scale according to a manageable number of agro-ecological variables in Kermanshah province, Iran in 2013 to 2017. Disease severity rating was varied by cultivar, disease-assessment date, and sowing time. Kruskal-Wallis one-way ANOVA determined a high area under disease progress curve (AUDPC) based on disease severity rated in 2016. A greater AUDPC was detected for early disease onset than late onset. Later sowings had greater AUDPC values compared to earlier sowings. From Principal Component Analysis (PCA), four principal components accounted for 88% of data variance. From PCA-based regression analysis, earlier powdery mildew onset corresponded with further rainy days and higher wind speed in spring, later sowing and maturity, lower disease resistance, and warmer growing season of commercial wheat cultivars. The present findings recognized proper sowing time as effective as genotypic resistance for sustainable management of wheat powdery mildew and provided valuable information on cultivar, disease, maturation, sowing date, and weather interactions.