Do you by chance live in a town? If you do, I would call animal control. We are a very small community, but we do have a leash law. DH happens to be the animal enforcement officer and he has to go talk to people occasionally about letting their dogs run lose. If they do not comply, he has a county deputy come talk with them. This usually works.
Might try a water gun, one of those made for the older kids to chase each other with.
Might try a water gun, one of those made for the older kids to chase each other with.