a powdery mildew (Podosphaera spiraeae)

a powdery mildew (Podosphaera spiraeae)

Observation - a powdery mildew (Podosphaera spiraeae). Description: Unlike many fungi, powdery mildew seems to prefer dry weather when, presumably, plants are stressed and less likely to be able to fend off attack. We're beginning to see a few of them around. Powdery Mildews attack a small range of hosts: this is the one

Unlike many fungi, powdery mildew seems to prefer dry weather when, presumably, plants are stressed and less likely to be able to fend off attack. We're beginning to see a few of them around. Powdery Mildews attack a small range of hosts: this is the one that attacks Meadowsweet (Filipendula ulmaria).
Edit: Changed to match AlanS's ID. Many thanks.