California law requires landlords to keep their properties in livable condition. Unless a tenant’s own behavior leads to a pest infestation, the landlord is responsible for paying the exterminator. If a landlord refuses to do so, tenants have several options for addressing the situation, including deducting the cost of an exterminator from the rent or simply terminating the lease and moving out.
via Does a California Landlord Pay for Pest Control on a Rental? | eHow.com.