Photostabilization of biocontrol agents by berberine

We studied the photostabilizing effect of the isoquinoline alkaloid berberine an the following three model photounstable biocontrol agents: the bacterium Bacillus thuringiensis (Bt), the baculovirus Spodoptera littoralis nucleopolyhedrosis Virus (SINPV), and the entomopathogenic fungus Beauveria bassiana. The photoprotection provided by berberine was evaluated following Various periods of simulated sunlight-UV irradiation. Insecticidal activity of Bt and SINPV, as well as the rate of B. bassiana spore germination served as parameters for the photostabilizing effects. Only a berberine-Bt complex is effective, as practically no photostabilization was evident by just mixing the two components. The UV-sensitive SINPV and B. bassiana spores were considerably photostabilzed by berberine. The role of the cationic nature of the berberine molecule and the importance of its absorbance spectrum in photostabilization of biocontrol agents are discussed.