If you use any pesticide incidental to your gardening or landscape business, you must have a Maintenance Gardener Pest Control Business License from the state Department of Pesticide Regulation (DPR).
Pesticides are defined as herbicides, insecticides, fungicides, rodenticides, and any substance used to control pests including weeds, snails, slugs, and gophers. Some examples of common home-use pesticides used by Maintenance Gardeners are Round-up, Gopher-Getter, Trimec and Malathion. Some fertilizers contain pesticides.
When these and other pesticides products are used as part of a gardening service, your business is required to be licensed by DPR and you need to register annually with the Agricultural Commissioner’s Office in the county in which you use pesticides.
See DPR's website to learn more: https://www.cdpr.ca.gov/docs/license/mgardener.htm