Cal. Food & Agric. Code § 6925
It is unlawful for any person to move, any nursery stock from one locality to another locality within the same county under conditions provided in Section 6926 or from one county to another county within the state, except nursery stock which is accompanied by a valid nursery stock certificate, unless such person forwards, at or prior to the time of shipment, to the commissioner who has jurisdiction at the destination, a manifest which states all of the following:
(e) Name of the carrier by which the shipment is being transported, whether by freight, express, mail, truck, boat, airplane, or otherwise.
The requirement for a manifest does not apply to any shipment of seeds.