Cal. Health & Safety Code § 2857

Whenever a nuisance exists upon any property, either in the district or in territory not in the district but so situated with respect to the district that pests from the territory migrate into, or otherwise encroach upon, the district, the district board may notify in writing the owner or party in possession, or the agent of either, of the existence of the nuisance. The contents of the written notice shall conform to the requirements of Section 2858.