Legal Question in Landlord & Tenant Law in Missouri

If you have no agreement, then you are a trespasser or a squatter. those folks have no duty to don anything, but are copmpletely liable for all damage that occurs while they unlawfully inhabit the space. Perhaps you mean your tenancy is by verbal agreement between you and the landlowner or his agent. In that case you do have a lease agreement. The answer to your question is very fact specific. If the City claims the property as a nuisance, then the landlord is the one that will be cited and maybe fined. If you know of the problem and do nothing to alleviate it, you may be liable to the landlord for his later expense of curing the problem. If you spray, put down some ant traps, and tell the landlord about the problem, you may have fulfilled your obligation. Different facts could put the onus all on you or all on the landlord.

Good luck