We recently planted a black chokeberry bush in our backyard. We live in northern New Jersey where the weather has been hot and humid over the last several weeks. The plant was doing great until last week when I noticed a white powdery substance on the leaves, which I thought to be mildew. I purchased an organic product online. However, the plant seemed to be getting worse, so after looking at some websites, I mixed together hydrogen peroxide/baking soda and water (2 tbl of 3% peroxide, 2 tbl of baking soda and 4 to 6 cups of water) and sprayed the plant. The mildew is gone but now many of the leaves are turning black and appear to be dying. What should I do to save the rest of it, and should I apply the product that I purchased for the mildew when it arrives?