Get two cans of Wasp and hornet spray, the kind that shoots 25', after sundown and when it is almost dark, they will all be on the nest, have your wife to get on one side of the tractor, you on the other side and at the same time spray the crap out of anywhere you can reach, walk away and leave it untouched for a day, then open it up. I have never had the wasp spray hurt anything. I used to get yellow jackets under my old Craftsman riding mower hood when I left it outside all spring.
I get this at Amazon, It is less than $4.00 a can.
BTW, I have been told by averyvery good source that she carries a can of this in her car and when someone pulled up to her side of her car in the bad part of Houston and started to talk bad trash to her, she shot a stream of this thru his car window and then she drove off, he didn't follow her either.