Seems like once I get farms up, my people don't forage any more. There's all that nasty fungus some loons seem to like to eat out in the boonies. It would be nice to pick it for emergencies and what have you. Instead they tend to just farm. The problems compounds when you take casualties.
I feel like part of the issue here is that what a colonist decides to do depends on priorities, and closer jobs will tend to have higher priority than distant jobs (so if foraging and farming are otherwise roughly equivalent, farming will tend to be favoured). That said, farming jobs appear on the list spontaneously, but only in short bursts. There's no real harm in leaving a foraging job queued up in the list, for whenever someone has the time to do it.