An object of the present invention is to provide a method for preventing and controlling powdery mildew which can achieve a high control effect by simple operation. The powdery mildew control method of the present invention is a powdery mildew control method in which nano-bubble water is applied to a plant body.本發明的課題在於提供一種可藉由簡便的操作而達成高防治效果的白粉病的防治方法。本發明的白粉病的防治方法為將奈米氣泡水施用於植物體的白粉病的防治方法。