For most critters that chew on things you don't want them to chew on:
Steep a couple of tablesoons of cayenne, 2 cloves of garlic and a small onion in 2 quarts of water. Strain the stuff out and spray it on plants or whatever. Drawbacks: whatever you spray it on stinks, (your house stinks when you make it, and when you spray it, for Pete's sake - stand up-wind!) and you have to re-apply after it rains. Pluses: environmentally friendly, and bees don't notice it. Letting the same stuff sit in oil makes a solution that seems to work when you paint it on wood.

For stale cookies, put a slice of fresh bread in an airtight container with them.