Cayenne pepper, white vinegar, ammonia and citrus all emit strong odors that dogs dislike, making them good dog repellents. For outdoor use, sonic devices and motion-activated sprinklers can scare away wandering dogs.
Ammonia and vinegar kill plants, so they should never be used on them. However, they can be sprayed on the perimeter of some properties to help deter dogs. Cayenne pepper or orange rinds can be sprinkled on a lawn. There are also commercial products that use these ingredients to repel dogs. Sonic pest control devices, which emit a high-pitched noise that humans cannot hear but animals find irritating, can be useful for discouraging dogs from lingering. Motion-activated sprinklers work well for some dogs, but other dogs enjoy sprinklers and may want to stick around to play.