Yes, please, tell me how you have any food at all if you never trained any farmers? Because the only way to keep them from harvesting is to either never train a farmer, or to wait for all your farmers to die. Even without being checked for farming, if they have the skill they will still strip trees - perhaps not as zealously, though.

By 'replenish,' do you mean boosting all the way back up to 1000 fruit? It sounds like you might be. That is an event-based boost. The trees get boosts of 111 fruit every 3 hours - there's no other regular replenishment, only event-based refills.