Is it necessary to remove old wasp nests?
Personally I had lots of wasp nests before, and after "exterminating" few of them I left them where they were. No more wasps in there. One thing - I used one of the "wasp killers" so that I was sure there will be no more chance to get wasps here. But one thing - if wast nest was removed there was a bit more chance that wasps get in here one more time building another nest. Try to use really good wasp repeller. Those chemicals do it right.