Two experiments were conducted in 2013 and 2014 at El-Bostan Farm at the north coast of Egypt. Powdery mildew is one of the most serious foliar diseases effecting several crops. The main objective of this study was to evaluate the effect of compost solution on disease severity of powdery mildew infected pepper and cucumber plants. The treatments iculude injection of compost solution into drip irrigation system and three foliar sprays  of organic solution treatments (control, once per week and once per two weeks). Data indicated that organic solution improved plant growth and yield during the two successive seasons. Combination between injection and foliar treatments using compost solution greatly decreased the severity of infection by Leveillula taurica,on pepper Sphaerotheca fuliginea on cucumber and significantly increased plant yields, compared with the single treatment. Combination treatments were the most effective, when compost was applied for twice / week. Economic analysis suggested injection of compost solution twice a week in addition to foliar application once a week  can save 40% of the mineral fertilizer beside saving  61.7% of fungicide, compared to a system with mineral fertilizer application  only.