Responsibility for Pest Control

Other

My tenants have notified me of an ant problem and have asked me to deal with it. Does anyone know who is financially responsible for this? I have been letting the house for three years after I carried out a complete renovation including new doors, new windows and new rendering. My previous tenants did not mention a problem with ants so I think this is the first time it has arisen. On my last property inspection, I noticed that there were quite a few crumbs and bits of food debris on the kitchen floor and I suspect open doors and windows have allowed the ants to come in and clean up. My concern is this, if I pay for a pest controller to deal with the ants, it is likely that the problem will reoccur if food waste continues to be left on the floor and I will be faced with a continuing bill. Does anyone have any advice on this?