Definitely no mothballs…they are bad for you, the environment, everything. Bad chemicals in those, to say the least. Here’s a post I did months ago when this question came up…with some good links in it as well. https://awaytogarden.com/mole-patrol By the way, are you certain that you have voles and not moles? I have both in different areas, and their behavior is a little different. I use mousetraps for both. Read the above, and let me know what else you need.