The present invention provides formulations and methods for preventing, suppressing, treating, or controlling pre- or post-harvest disease or decay in plants. In the inventive method, plants are contacted with a formulation including an antagonistic microorganism and a booster composition. The booster composition generally includes about 3 parts Kaolin clay, about 1 part yeast, about 1 part Yucca plant extract, and about 1 part calcium-source material. The antagonistic microorganism may be included in an amount of between about 0.02 parts and about 0.5 parts by weight of the formulation, with about 0.04 parts antagonistic microorganism being preferred in testing to date. The formulation is typically applied to the above ground structures of the plant, including its leaves, flowers, stems, trunk, blossoms and fruit.
