I can't scientifically prove this works, but I will say I tried it because I had a nice little shady garden full of ornamental plants when I was living in an apartment a few years ago that my slob neighbors would allow their dogs to poop in. I got a big jar of cayenne powder and sprinkled it around the area every time that happened and it seemed to do some good.Dust them with cayenne. One taste will keep them away.