I just took a look at Tarrific Garden Tonics by Jerry Baker, I beleive what you have is mildew growing on the leavesdue to the rain and hot weather. I noticed it yesterday on my Karaganis here in Yellowknife, NWT Canada. According to Page 179 of Jerrys book you can buy a store bought ehemical for this or mix up your own and try it. test it first please I have not tried this my self 1tablespoon of baby shampoo 1tablespoon of hydrogen peroxide 1 tea sppon of instant tea granuales 2 cups of water Instructions mix these ingredents in a hand held sprayer and apply to affected leaves and buds. Mid afternoon on a cloudy day iof the bes ttime to apply it.