Does the mildew that sometimes get on old forget-me-nots (Myositis) also infect or make worse the fungus that attacks hollyhocks (Malvaceae). I ask because even though it has been exceedingly dry and hot my holyhocks are covered in fungus.
I have read that there are many varieties of powdery mildew. One that affects a certain plant may well not affect another. The type of powdery mildew on squashes does not, apparently, spread to tomato plants. I once saw mildew-free tomatoes growing under mildew covered lilac. Whether the two sorts of plants you have share the same type of mildew is not that easy to find out!
