There are several types of fungus that cause Powdery Mildew. The mildew appears on the surface of leaves and other parts of a plant as a powdery grayish-white substance. Grape Ivy, Begonias, and African Violets are prone to this disease. Powdery Mildew causes the tissue in the leaves under the fungus to die. This results in leaf-drop and a general decline in the growth of the plant. Immediately remove all dead or dying leaves and those that have dropped to the soil. Move the plant to a less humid area with better air circulation and keep the leaves dry. As with the other fungal plant diseases, use a commercial FungicideFungicides are chemical compounds that are used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage to your houseplants. or the homemade remedy of putting a few tablespoons of baking soda and one or two teaspoons of mineral oil in a spray bottle of water. Shake well and spray all parts of the plant.