My 6 month old Sheltie has chewed up the wood molding on 2 of my walls. He does this when I am away at work. I have no choice but to leave him home alone for 8 hrs 5Xs a week. He has plenty of chew toys and bones. I bought some bitter apple spray the first time he did this but it doesnt seem to work.. How can I correct his behavior if I cant catch him in the act?