I found the following in regards to your questions:
White mold can be dangerous. Especially in that it can affect other plants as well especially if left untreated.
Young foliage and shoots are the most vulnerable to further powdery fungal growth. This mold does not kill the plant but will quicken its loosing leaves, prevent flowering and cause plant to go to sleep.
As to how to eliminate; these two possibilities seem effective and most inevasive:
Potassium bicarbonate- Similar to baking soda, this has the unique advantage of actually eliminating powdery mildew once it’s there. Potassium bicarbonate is a contact fungicide which kills the powdery mildew spores quickly. In addition, it’s approved for use in organic growing.
Baking Soda (sodium bicarbonate) -This is possibly the best known of the home-made, organic solutions for powdery mildew. Although studies indicate that baking soda alone is not all that effective, when combined with horticultural grade or dormant oil and liquid soap, efficacy is very good if applied in the early stages or before an outbreak occurs.
Use this recipe to make your own solution—mix one tablespoon of baking soda with a teaspoon of dormant oil and one teaspoon of insecticidal or liquid soap (not detergent) to a gallon of water. Spray on plants every one to two weeks.
sources: http://www.ehow.com/how_5641167_remove-white-mold-plants.html
: http://www.ehow.com/how_7873930_rid-mold-plants-vinegar-mix.html
:http://www.growingagreenerworld.com/controlling-or-eliminating-powdery-mildew/
