Cal. Food & Agr. Code § 12031
Each agricultural pest control adviser who makes any recommendation for agricultural use shall register in person with the agricultural commissioner in the county listed in the adviser's address on the license issued pursuant to Article 2 (commencing with Section 12021) or with the director if the county does not have an agricultural commissioner. If the address of the adviser on the state license is not within this state, the registration shall be in the county of occupational choice. Registration in any additional county shall be made by mail or in person, at the discretion of the commissioner of the additional county. The additional registration by mail shall be made on prescribed forms which may be obtained and processed in the county listed in the address of the adviser on the state license or the county of occupational choice, as the case may be.
Ca. Food and Agric. Code § 12031