i have a 10 week old shih tzu who barks and bites at my 5 year old yorky do i stop this or leave them to it my yorky does not like it and showes her teeth i am worred she will hurt molly

Your Yorkie will be best at teaching the new upstart good canine manners.

Whilst your Yorkie should be the one to do the teaching, it's often best to make sure the puppy doens't get the chance to bully the older dog as some older dogs just don't know *how* to teach canine manners :(

my border collie tried this a couple of times with our chinese crested bitch, and we watched her reaction as he could of killed her, she showed her teeth and then the teeth and a warning growl, and if he still persisted in annoying her,but by this time i was starting to edge towards the end of my seat ready to wade in and reprimand him, she would then teeth warning growl, eye contact and then she would fly at him teeth going and nip at him and the gnashing of teeth from her was terrible to hear but he soon backed off, she did this to the rottie and my hubbys english bull terrier, she is still the boss over all of the boys and they could just sit and squash her if they wanted to, i have never had to tell them off for playing to rough with her, you normally hear her name being shouted to leave the boys alone,
but if things do get to much you could put a long line on him trailing around near you and when he persisits on going over the top on you little dog you can quickly call him off and with a tug of the line you can get him to you this might help.
keep us informed
carol