Taggart is chewing wood!

[Taz_Zoee]

He is eating the deck and Bruce is not happy. Bruce designed and built this deck.
When we catch him doing it we make him stop, but we are not outside with them ALL the time.
I just did the poop scooping (which hadn't been done in a LONG time ) and even his poop looked like wood. He is chewing on the step, one of the posts of the fence and another step to the hot tub.

Any suggestions on how to stop this? Bruce put the Phooey (like bitter apple) on it but with the rain it doesn't last. Plus I think the taste doesn't bother Taggart. I had put it on Zoee's collar tag thingy and he still pulled it off. Is there anything that can be put on the wood?
I have attached some pictures of the damage.

Thanks.