I would not prune unless you have to - instead I would spend some time checking your dog whenever it does wrong - show him who is the leader of the pack (lol)

Thanks - done both of those!! I don't let him do it any more!
I did buy one of those Pee Posts but it doesn't work.
Maggie

Don't punish him. Praise and reward him when he goes somewhere else, but not when he goes there. Eventually he should learn that it isn't worth going in that spot.
Regarding the plant I think I'd keep a watering can nearby as suggested above, and wait and see whether the branches recover in the spring.
Incidentally, have you tried a repellent spray in the area? These don't always work but it might encourage him to find somewhere a little more inviting!

However, pieris do respond to cutting back quite well.

Why would a dog pee from a water can or hose Snoopdog?

Amazing what you can teach a dog! Blimey, better get mine out doing the garden!

He's obviously speaking from experience Myron. Can we have a video Snoop?

I see we have a comedian on here, thanks Myron