Bed bugs in main house

[Corissa Rogers]

Hello one of the rental houses has discovered bed bugs in the main house. There is a mother in law house on the same lot towards the back of the property. Do both houses have to be sprayed? The back house was sprayed 6 months ago and the tenants took necessary procautions to prevent future bed bugs ( fully encased beds and use of professional chemicals) but the main house decided not to spray at the same time. There are not bed bugs currently in the back house.  The rental agreement does not cover pest control