Armadillos are very tough and resilient animals, and being an invasive species in North America they have been very successful. Having a well-armored hide they are very good at being bad prey for predators, and this lack of predators also has another effect. Because the majority of repellents are based on predator urine, this means that there really isn’t any effective repellent that will keep armadillos from your garden and property.
Some people will actually like having armadillos in the area as they do eat insects and other pests, but can quickly become a pest themselves. Removing them is really the only option, and for those who aren’t confident to do it themselves, most areas will have a wildlife removal expert who can take of the problem for you and get rid of the armadillo.