Definitely a fungus, and not sunburn?

No, I don't think it is sunburn. It seems to be fine most of the summer until about mid-August then gets brown leaves really bad. I am going to move it to a part shady area and see if that has any effect on it. I have had very little response so guess I am the only one with the problem.

No, I planted a Nugget Ninebark this year, and have the same issue. A profusion of small brown spots all over the leaves, and the leaves are generally quite small and perhaps a little burned-up looking. I have been remiss on my watering, so that is a possible cause.

my vib. onondaga are doing this now, but we have had plenty of rain this summer. i lost my gold. 9bark a few yrs ago; I think same symptoms as yours.
best,
mindy

I live in southern maine and have 3 red and 3 golden ninebark.....the red ones are doing well....but the golden ones are like yours......they are in a wet area....that gets a good deal of sun. They end up looking dry and burned but it definately looks like a fungus or insect? problem....not sun burn.

I was thinking of giving them a shot of miracle grow as a tonic.....I know its definately not organic...but sometimes it seems to help.