Hire a professional pest control company with the expertise to eliminate pest problems. Self treating can make the problem worst by repelling insects and spreading the problem to surrounding units.
Allow for ample time for service dates so that the tenant can be properly prepared and notices to enter are handed out. This will reduce the number of times a unit needs to be treated. Have surrounding units of a problem unit inspected.
When a tenant refuses service make sure you get back into that unit in a timely time frame to reduce further spreading throughout the building.
Be proactive and have your units treated prior to a new tenant occupying. They may bring pests into your building from another building.
Contact your JAPCO professional to provide you with a free estimate for your apartment buildings.