Hi Tom,

thank you for contacting us at the UNH Extension Infoline for Yard and Garden.
You may have read the recent Question and Answer I wrote on the topic from the Granite State Gardening newsletter, or the NHDAMF Weekly Market Bulletin.

Yes, unfortunately, mothballs are often misused for repelling rodents or other wildlife, but there is little evidence to support that they are actually effective for safe and long-term control.

Alternatively, the most effective strategies for keeping mice away from your home's foundation is to first evaluate where they might be able to come into the house and work on sealing and filling up any openings or access points that mice may be able to enter. In step with doing that, reducing any "attractants" such as pet food, birdseed, or trashcans and maintaining a clear 2-3 ft. border around the exterior of the house that is free from debris or clutter discourages mice from finding shelter around there.

I realize that it may sound simple enough, but isn't always easy depending on the building.

The second strategy is to implement snap traps - they're safe, easy to set up, and can be effective for keeping mice in check at low population levels.

Rodenticides are always the last option we emphasize, and should really be considered only if you have a major infestation, with the advice of a licensed pest management professional.

Repellents overall have not shown to be very effective, whether it's mothballs or essential oils, or another home remedy - that's partly because they contain volatile active ingredients that can rapidly disappear when introduced to the environment. At best, they may provide some temporary control, but not in the long-term.

Although you may certainly choose to continue doing some research into alternative repellents, I can't provide any recommendations that haven't been supported through research and more thorough investigation.

NC State University has a good resource that describes each mice management method in more detail - https://content.ces.ncsu.edu/surveillance-and-management-of-common-structure-invading-mice

I hope that this information is useful for you, but please let us know if you have further questions!

-Steph Sosinski