Powdery mildew is a fungal disease that causes a serious reduction in both root and sugar yields in sugar beet areas in Egypt. This study aimed to determine the effect of three water stress treatments namely, IR1 (recommended irrigation times), IR2 (3 withholding irrigation times), and IR3 (4withholding irrigation times) on powdery mildew infection severity and yield components of ten sugar beet varieties. The experimental design was a split-plot design with three replications at Al-Fayoum Governorate, (29°17ˋ N; 30°53ˋ E), Egypt, during 2017/2018 and 2018/2019 growing seasons. Results showed that disease severity varied significantly under the three water stress treatments, which were about 21.02, 18.71, and 16.60 %, respectively. Meanwhile, IR3 (4 withholding irrigation times) is more effective in the control of powdery mildew disease, but it is the lowest one in yield components traits. Varieties i.e. Heba, Pleno, Beta 382 and Sibel registered the lowest values of disease severity percentage (11.77, 13.64, 14.90, and 16.40%, respectively). Withholding of irrigation had a significant effect (P< 0.05) on sugar and root yields so that IR3 water stress treatment registered lower yield (2.78 and 18.53 ton/fed) than IR2 water stress treatment (3.17 and 22.60 ton/fed). As a result, growing sugar beet under IR2 water stress produced higher sugar content and less amino-N and Na accumulation in the root, as compared to IR3 water stress. The lowest disease severity percentage (11.77%) along with the best root yield (22.20 ton/fed) was observed in Heba variety. Sugar beet varieties i.e. Heba, Beta382, and Sibel registered the highest value of oxidative enzymes (catalase, peroxidase, polyphenol oxidase), and we can be recommended these as tolerant disease varieties. Skipping one or more irrigation to reduce the powdery mildew disease was recommended.According to the results, the stress tolerance index (STI) and of geometric mean productivity (GMP) appears to be a suitable selection index to distinguish tolerant sugar beet varieties for water stress. Breeders should focus on the performance of varieties with high root yield in diverse environments and high extractable sugar.