The spores are spread by air currents and do not require water to germinate. In the early stages, powdery mildew spreads very slowly and, if noticed, can be controlled fairly easily. African violets and begonias are often affected by powdery mildew. Prevention Most of the disease problems touched on in this article can be prevented by good cultural practice, cutting off the damaged parts, being careful when watering, and by moving the plants to a drier, well ventilated area. If the problem persists you may need to treat the plant with a recommended fungicide.
Fungicides are chemicals that are able to prevent or cure diseases caused by bacteria or fungi.
They are classified into two types protectant sprays prevent fungal spores from spreading to the plant and eradicant sprays prevent further development of diseases that have already started. Fungicide use in the home should be a last resort. Read the label and follow general pesticide safety rules.