labrador wont poop in the yard

Question
I have a five year old full lab and I have walked him since he was a puppy.  we just had a fence put in for him and he will not go poop inside the fenced area.  He will go at my sisters and her yard is fenced. Help!

Answer
Teach him a word that means "go poop" (that's what I use, but some people prefer "hurry up" or some other phrase).  Every time you walk him, or he poops while at your sister's house, say "go poop" and hand him a reward or tell him good boy.  Once he starts realizing that he is being good, he may look up at you expectantly for his reward.  At that point, you can start to say "go poop" beforehand, and he will, at least, know that you WANT him to defecate.  That might help him realize that the new fenced area is ok to use for his bathroom.