The disease is caused by a group of fungi that each attack a specific plant species. It causes unsightly damage to leaves and even flower buds, weakening the plant and sometimes even killing it. It is prevalent on a variety of ornamental plants including roses, hydrangeas, pride of India, and most vegetables.
Powdery mildew is visible as felt-like white powdery covering on leaves or flower buds, turning greyish with age. Young growth can become distorted and scabby, eventually leaving scorched patches on the plants.