Depends on where you are and what you have around you. Here in northern Wisconsin the deer are still running on mainly acorns
There are virtually no acorns on the property that I hunt. I do know that last year, the deer were hammering the picked corn field once the temperatures started dipping around 30. Around here, their food source is typically apples and the alfalfa fields. The farmer actually just picked the corn field yesterday so I'm hoping for a cool swing in the temps soon and hopefully we'll start seeing more activity.
All depends on the amount of acorns available. I know here in NC there are a TON of acorns this year. It may be December here before they make the transition back to corn.