How does Bacillus subtilis control powdery mildew if sprayed in the canopy?
Bacillus subtilis is known to produce lipopeptides, which destroy the cell membrane of powdery mildew spores on the leaf surface. (ref AgraQuest).
These substances are produced by Bacillus during the manufacturing process and are present in the total fermented product. The live bacterium itself is less important than the substances in the liquid culture. Applications should not be made to ‘run-off’ so that the natural active ingredients remain in contact with the leaf surface and prevent powdery mildew spores form germinating.