I have never found a need to spray my hydrangeas with anything. What sort of fungal issues are you trying to prevent?

You are fortunate! We always have issues with black spot here. Lots of heat and humidity! But I'm amazed at how well the Rose Shield works - without any residue.

Do you water with sprinklers? Overhead watering can encourage Cercospora leaf spot (not the same as rose black spot) but this disease is seldom a big concern and tends to be more cosmetic than causing serious harm. Generally develops later in the season but as long as you practice good garden sanitation (pick up and destroy all the leaves each season when they fall), that is often all the "treatment" required.

Siting bigleaf hydrangeas in sufficient shade can help to reduce the incidence of this disease as well as providing good air circulation. And water only at the root zone, avoiding water on the foliage as much as possible.

Thanks for the tips. No, never any overhead watering & am a fanatic about picking up and destroying leaves. They also have good air circulation. I think a lot of it is our climate. My neighbor gave up growing hydrangeas because of the terrible looking leaves (black spot). But I love them, so can be quite persistent. :) They are worth a little spraying, in my opinion.