Hi our tenants ( live downstairs in desperate dwelling) are saying they have a fly issue and think its from a dead rat in wall as that's where most of the flys are sitting. They killed a heap yesterday but keep comming back. Upstairs where I live we aren't having an issue. They are getting pest control out to see where issue is- who pays? Landlord or tenant? I would normally try and fix myself but not much I can do in this case.