Answer: Boric acid powder might control the ants. I would also suggest you check with your county extension for their suggestions, they will have the most up to date recommendations for what can be used in MN and how/when is best to apply it. Hennepin County Cooperative Extension They are at 1525 Glenwood Avenue, Minneapolis, 612-374-8417.
As for the digging, without knowing what it is, it's difficult to suggest a method to foil them. You might try laying chicken wire or netting with larger holes on top of the soil, letting the plants grow up through it. Most creatures won't want to dig where they're feet get "caught" in the wire. Good luck!
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