You can cut the foliage stalks back to the ground as soon as the foliage dies and turns brown - no need to wait as long as October and if you have lily beetle issues, I certainly wouldn't leave it in place over winter! Personally, I prefer to leave a short stalk 2-3 inches) in place to mark where the bulbs are located so as to avoid stepping on them or other damage next spring when they begin to emerge.

Thanks for the advice! The beetles seem to have gone to ground for now - just in time for me to turn my attention to Japanese beetles!