You probably could. Civil Code section 1941 and 1941.1 impose statutory duties upon the landlord to keep the rental dwelling habitable, including keeping the building, grounds, and appurtenances at the time of the commencement of the lease or rental agreement, and all areas under control of the landlord, kept in every part clean, sanitary, and free from all accumulations of debris, filth, rubbish, garbage, rodents, and vermin.
Your proposed provision in the rental agreement would be based upon Civil Code section 1941.2, which imposes the parallel duties upon the tenant:
"(1) To keep that part of the premises which he occupies and uses
clean and sanitary as the condition of the premises permits.
(2) To dispose from his dwelling unit of all rubbish, garbage and
other waste, in a clean and sanitary manner.
(3) To properly use and operate all electrical, gas and plumbing
fixtures and keep them as clean and sanitary as their condition
(4) Not to permit any person on the premises, with his permission,
to willfully or wantonly destroy, deface, damage, impair or remove
any part of the structure or dwelling unit or the facilities,
equipment, or appurtenances thereto, nor himself do any such thing."
Frank W. Chen has been licensed to practice law in California since 1988. The information presented here is general in nature and is not intended, nor should be construed, as legal advice for a particular case. This posting does not create any attorney-client relationship with the author. For specific advice about your particular situation, consult with your own attorney.
While a landlord is generally required to maintain a unit in habitable conditions, which usually includes keeping vermin out, you probably could reach an agreement with your tenant to have them pay for pest control. From a common sense standpoint, having a tenant for 4 years is a pretty good thing for a landlord, especially if that tenant is a good one - paying rent on time, not asking for much, keeping the place relatively clean and well maintained. It might be worth the very limited monthly cost for you to pay for the pest control rather than lose or anger a good tenant.