Cal. Health & Safety Code § 2835

Upon a petition adopted by a four-fifths vote of the district board, or upon its own motion following the notice the board of supervisors deems sufficient and a public hearing, the board of supervisors, may, with the concurrence of the district board, add to, or delete from, the list of pests which the district may control. The board of supervisors at the hearing may also consider, and make changes in, the method of district taxation, as authorized by Section 2822.5, as though a new district were being formed.