Strains of the yeast Aureobasidium pullulans are used in biological crop protection and act by competing for space and nutrients at the site of infection of the pathogens.
The yeast cells grow on the stigma and flower base of plants in orchards, preventing infection by the fire blight pathogen Erwinia amylovora, for example. Or they grow in fine micropores of the fruit surface of pome fruit and thus block the growth of storage rot pathogens (e.g. Penicilium spp., Botrytis spp., Monilia spp., Gloeosporium spp.).
The yeast can be used even shortly after harvest, as there is no waiting period (no residues). Hazards for humans and animals are not known, the yeast is gentle to bees and beneficial insects.