No - its mildew of one sort or another, a fungal infection - some are worse in hot dry weather on some plants, some are worse in damp, muggy weather. Using a fungicide, particularly a systemic one, is a way to combat it. Alternatively, mix 1 part milk to 9 parts water in a sprayer and spray with that - said to work, but I don't know how well or how long for.

Agree with bamboo, have noticed powdery mildew on all aquilegias, delphiniums and other perennials recently, this will be down to the long dry spell.

I try on my plants with 2 parts water & 1 part vinegar and it seem to work also on ants too. Good Luck.

I'll have to give that a try, Lorna. Thanks. we've got powdery mildew, too, and I don't like using too many shop concoctions in the garden. Vinegar sounds much more organic! Annie
I might try the milk as well, but most of mine goes on cereals!! Ha, ha!!

Not sure I'd try vinegar - that'll bleach a worktop left on it overnight, but the milk thing has been scientifically tested and proven to work.