i use to have a thing to kill bees for people. it hooked up to a air tank then had a half inch valve with a tee one one side and a quick connect to a air tank on the other. on the top side of the tee nech it up to like an 1 1/4" pipe with bout 6" long and a cap that screws on it. on the other side of the tee put a long peice of 1/2" pipe and fill the big pipe up with 7dust and point it at the bees and open up the valve. it will kill the heck outta all of them. prolly be best to do it at night when they are all there and dont use a flash light or they will swarm you! if they havent been there long they will prolly move on tho. its just the time of tthe year they swarm and they are lookin for a new home. I use to work on a bee farm so i have seen your problem a few times