Wasps in a tree

[Jo]

I have a large ash tree in the garden I can hear wasps buzzing but looking into the tree I see nothing, at night though you can't go into the garden because as soon as any light goes on you get bombarded by wasps. The funny thing is I have a tree full of ripening apricots near this tree and they don't go near that at all, neither are we bothered if we eat or drink in the garden. They just hate the lights. Any idea what they are and how do I get rid of a nest I can't see?[8-)]