Re: powdery mildew
It is too late to try this year, but if you can spray the leaves with baking soda BEFORE the powdery mildew usually appears, than it will change the pH of the leaf surface, preventing the powdery mildew from growing there. You would need to reapply after rain and watering. As far as I know, the baking soda won’t make a difference, if you can already see white.
