Time to move this down. We have winter moths in this area so I presume this is the larvae stage that is eating the leaves. I still don't know what they look like.

I had a similar problem. It sounds to me like you have a Japanese Beetle investation. The reason you probably haven't spotted them is because they are only active for a few weeks in the summer months (June/July). The Larvae lives under your lawn and feeds off of the grass roots. There are bags that you stake in your lawn that attract and trap them. I've read that it's a double edge sword though. They trap your bugs, but they also attract more bugs to your yard. Two nights ago I used a insect yard spray that you hook up to your hose on my plum tree. I purchased it from Walmart but I don't know the brand. Anyway it seemed to do the trick ie kill them. Last night I sprayed the tree and lawn with soapy water in hopes of killing any remaining beetles in the tree and larvae in the ground. I mixed regular dish soap with water in a cup. I then attached the nozzle from the insect spray I had to the hose and used that to draw the soapy water up. Not sure if that helped but we'll have to see if they come back next year. I'll probably treat the yard a couple more times in the fall and spring.

Do we have Japanese Bettles in the PNW? I didn't think so.

We don't have Japanese beetles that I know of, but it is just a matter of time.

No Japanese Beetles here. (Thank goodness for small favors.)

That said, each of your trees could be eaten by different critters. We need detailed descriptions or, better yet, photos. Can you post any?

I think I saw some on a tree in Queen Elizabeth Park, Vancouver many years ago. You really can't miss these large conspicuous beetles clustered together on plants. If you had those there you would seem them on the trees, doing their work.

For a map...

Here is a link that might be useful: Reported Status of Japanese Beetle