Every occupant of a dwelling containing a single dwelling unit shall be responsible for the extermination of any insects, rodents or other pests therein or on the premises. Every occupant of a dwelling unit in a dwelling containing more than one dwelling unit shall be responsible for extermination whenever his dwelling unit is the only one infested. Notwithstanding the foregoing provisions of this section, whenever infestation is caused by failure of the owner to maintain a dwelling in a rat-proof or reasonably insect-proof condition, extermination shall be the responsibility of the owner.
('71 Code, § 156.40) Penalty, see § 152.99