Blow it up! When I was a kid a friend of mine and I blew up a nest in a tree. We had found it while hiking in the woods one day and remembered it later that summer when we got a hold of some M-80s. We grabbed some kite string and were able to tie it to a rock to toss over the branch that the hive was on. We then tied a M-80 to the other end of the string (from the rock), taped a lit cigarette on to the case and fuse (to delay the blast) and quickly pulled the M-80 up into the tree next to the nest. I set the rock down to hold it in place and we got the heck out of there. We got about a quarter mile away before BOOM!
We chickened out and decided to come back the next day to see what was left. When we did all we found were bits of nest and some dead wasps scattered around.