A method sometimes adopted where insecticides are not acceptable involves fastening come of cardboard over the entrance into the wall, with the broad end against the wall over the problem area, and the small end (about 6-10mm across) outwards.  The bees can leave and resettle elsewhere, but they cannot re-enter the small aperture of the cone, so gradually the hive dies out.   If the hive has not been established for any length of time, the entire hive may leave.