Beginner Gardening: MOLD ON BEGONIA LEAVES, 1 by hcmcdole

hcmcdole wrote:
Try Neem oil (it has a strange smell so you might want to take it outside to spray). It is organic and you can get it at Home Depot, Lowe's, Wal-Mart, and nursery stores either in a ready to use hand sprayer or in concentrate form. Other fungicides should work too but follow directions carefully. Some home remedies are diluted milk, a baking soda mix, and Lysol aerosol spray for mildew (this may damage the leaves though). Sulfur or copper dust is supposed to work if you want to look for it and dust it on the leaves.

Here is what powdery mildew looks like on a cane begonia leaf.