As I understand in Colorado the Landlord is ultimately responsible to cover costs of pest control. However, I have seen LLs put in the lease that the unit is guarunteed pest free at time of move in and any costs during the term of the lease is tenant responsibility. I have a tenant that has a mice phobia. In my experience, mice problems can be controlled by a handyman and yearly costs to an exterminator are not necessary. What to do if a tenant is wanting yearly pest control which can get expensive and the LL wants to simply handle a couple mice with setting traps. It is not an infestation.