A method for preparing a stem cell-based, human derived composition containing conditioned cell culture medium is disclosed. The method comprises culturing cells of two or more eukaryotic cell lines to form conditioned culture media, separating the cultured cells from the conditioned culture media, and combining conditioned culture media to form a bioactive composition. This composition is used to treat citrus plants that have been infected by one or more insect-vectored bacterial and/or pathogenic infections such as Citrus Greening. This method consists of applying the conditioned media one or more times to the plant. Use of this treatment may have application to a variety of other agricultural conditions.
