Will moth balls poison the soil?
Moth balls may have been suggested in the past for repelling wildlife from gardens, but this is an illegal pesticide use and probably ineffective. The moth balls present an attractive nuisance to both children and wildlife and if eaten can be toxic.
You did not mention the type of garden you are referring to, a vegetable garden or ornamental beds. In either case, we recommend that you remove the moth balls and discard them. In a vegetable garden they are not labeled to be used around food plants. Moth balls can kill organisms in the soil. It would be okay to plant next spring. The moth balls will not harm the plants in an ornamental bed.
Squirrels can be difficult to deter in gardens. You did not mention the specific issue you are dealing with. Here is our publication on nuisance wildlife and some management options page 3. http://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/hgic/HGIC_Pubs/wildlife/HG90%2...