Oh, I don't know. I've seen several japanese beatles around here too, more than normal. For some reason I keep finding them dead on my swing on the deck. Don't know what is killing them, but what ever it is I hope it keeps it up. The only thing I have sprayed is wasp/hornet killer. I've killed three huge hornets this past week on the deck, must have a nest somewhere in a neighbors tree.
I agree with the others, that don't look like Japanese Beatle damage to me either. Did this happen quickly, or maybe after a bad storm?
Kim