White fuzzy mold, also known as powdery mildew, is caused by the airborne spores of fungus. The fungus spores generally attach to a young leaf where it is able to germinate and grow, quickly spreading to other parts of the plant and nearby plants. Both indoor and outdoor plants are susceptible to infection, especially in warm, humid areas.
It could also be mealybugs which commonly leave a white residue on a plant’s leaves that resembles cotton. You will find this residue mostly on the stems and leaves. This residue is either the egg sacs of the mealybugs or the pests themselves. You may also find that the plant has a sticky residue on it. This is honeydew and is secreted by the mealybugs. It can also attract ants. Mealybugs look like small, flat oval white spots on plant leaves. They are also fuzzy or powdery looking.
Google either one and they have several remedies or go to your local plant/gardening centre and ask for a pest/mold control. Good luck!