The use of safe alternatives to fungicides has become an important matter of urgency due to their toxicity and development of new strains have capabilities to overcome the efficiency of fungicides. In the present study, six treatments, i.e. the control (water only), Penconazole fungicide (5ml/20L), dipotassium phosphate (50, 75 and 100 Mm.), Nanosilica (300, 500 and 750 ppm.), Propolis extract (5, 10 and 15%), garlic extract (5 and 10 %) and Alga Grow-4 (1ml/l.) as alternative means to fungicides were investigated against zinnia powdery mildew. In vitro study showed that dipotassium phosphate and garlic extract were the most effective in reducing the conidial germination percentage. The reduction percentage was increased by increasing the tested concentrations. Under natural conditions, spraying plants six times with one week interval, showed that dipotassium phosphate and garlic extract, respectively, were the most superior treatments which significantly decreased disease severity and improved the number of flowers/plant, chlorophyll content, oxidative-reductive enzymes (POX and PPO enzymes) and total phenols. On the other hand, the reference fungicide showed the highest efficiency.