The present invention describes methods and formulations for protecting plants against various pathogens, involving the use of Prunus maackii materials. In some embodiments the biopesticide formulation comprises of at least one flavonoid such as 3,5,7-trihydroxy-6-methoxyflavone, 3,5,7-trihydroxy-6-methoxyflavanone or 5,7-dihydroxy-8-methoxyflavanone. The invention further provides a method of making the biopesticide by extracting a Prunus species with a solvent and formulating the composition using adjuvants, and kits for application of the biopesticide.