Study on the infection status of powdery mildew of grapevine in three county of Sistan region, Iran

Grape powdery mildew (PM) caused by plant pathogenic fungus Erysiphe necator, is the most important disease on grapevine in world and Iran. In order to study the spread of this disease in vineyards of Sistan region, 30 vineyards in three county including Zabol, Zahak and Hamoon were selected during years 2017 and 2018. The vineyards were visited on a weekly basis to record PM incidence (I) and disease severity (S). Based on disease incidence, there were no significant differences between counties and vineyards in first, second and combined two years, and in combined two years Zabol and Zahak (57.6%, 57.2%) had the highest and lowest percent of disease incidence.Based on leaf and fruit disease severity, there were significant differences between counties and two years (P <0.001) and in combined two years Hamoon and Zahak (23.1%, 20.6%) had the highest and lowest percent of infection in leaves. Based on the fruit disease severity, Zabol and Zahak (25.4%, 21.8%) had the highest and lowest percent of infection in fruits respectively. Based on area under disease progress curves, there were no significant differences between years, counties and vineyards in disease incidence but in leaf and fruit disease severity, there were significant differences between years and counties and in combined two years Hamoon and Zabol (696.9 and 680.3) had the highest of leaf and fruit infections respectively.