bobm46 writes:

But I am somewhat surprised that no one has yet
suggested a paintball gun to discourage the dog.

Many pet owners consider their pets as family members, and if one's family
member were to trot in with a humiliating splash of paint, a certain rage
against the marksman would ensue. I dislike pets and especially their
wandering fecula deliveries, but I do value comity with my neighbors. Once
offened, a neighbor tends to remain a permanent enemy. So if one were to
attempt this dubious strategy of launching missiles against the intruders,
discretion would be indicated, and paintballs are the very opposite of
discretion.

Not to mention making a mess of your own landscape.