The house and barn I just bought was not very well maintained. In the attic of the house there are about 50 abandoned wasps nests (as it is winter). The barn has well over 100. I know I need to eradicate any entrance points into the house and barn for wasps, but do I need to remove the old nests, or is it ok to leave them? I wasn't sure if they reuse existing nests or not or if there was an advantage to removing old ones.
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.