What's the problem with some scorched earth strategy? Thinking like a hopeless Lord losing his region, I certainly would not leave food for my enemies... or gold in the temples... I would go to the extremes of destroying the fortifications and recruitment centers, rocket-launch the taxes to the heights and cause as much damage as possible.
It is not as if historically this has never been done before...
However, if a takeover is already under way, you definitely don't have control of the region enough to empty the granaries.