I have found that adding pineapple to the diet helps to stop this.
On a lighter note...if you are around using the "leave" command helps of course provided that your dog understands and complies with it. For some reason which now escapes me, instead of teaching my dogs the usual word "leave" I taught then to give thing up on the command "mine"....which is fine until the neighbours hear you apparently telling the dog that a pile of poo is yours!!