Cal. Health & Saf. Code § 116135
The board of supervisors of each county and the governing body of each city, whenever it may by resolution determine that it is necessary for the preservation of the public health or to prevent the spread of contagious or infectious disease, communicable to mankind, or when it determines that it is necessary to prevent great and irreparable damage to crops or other property, may appropriate money for the purchase of, and may purchase, poison, traps, and other materials for the purpose of exterminating and destroying rodents and abating the conditions listed in Section 17920.3 that are causing the infestation in that county or city, and may employ and pay inspectors, who shall prosecute the work of extermination, destruction, and abatement on both private and public property in the county or city.
Ca. Health and Saf. Code § 116135