A biodegradable formulation from petroleum waste in comparison with the systemic fungicides difenoconazole+ azoxystrobin combination at concentrations of 250 and 325 (µg/ml), respectively was applied as a foliar spray for the control of powdery mildew of cucumber caused by Sphaerotheca fuliginea. Plants were grown under the greenhouse conditions and two successive sprayins were carried out. The frist one was applied on 39-day-old plants and the second on the plants of  46days old. The results illustrated that the biodegreable waste has a potential to control the disease and  was  more effective in controlling the disease than the selected systemic fungicids. The results highlight the potential of this biodegradable formulation as a promising and economic method for controlling powdery mildew on cucumber. Also, it is less toxic on the plants than the used fungicides, while the plant constituents of phenols and chlorophyll were increased which are a clue for increasing the immune system of the treated plants. This biodegradable formulation from petroleum waste may be useful for controlling other diseases of cucumber or other crops.