How can you stop a puppy from annoying the hell out of an older dog?

We have a year old staffy x puppy and a 6 year old american staffy. the puppy spends her whole day annoying the big dog - she bites her, barks constantly at her, bites her tail, eats her poo and generally just annoys her. we do our best to keep the little one amused by taking her for daily walks, throwing for her continuously and giving her marrow bones but to no avail. would love to hear whether anyone might have any ideas about what we can do...