Bees or bumblebees go through a corridor and get ‘coated’ with biological fungicide powder when leaving the hive. The biological fungicide contains a beneficial fungus (Clonostachys rosea J1446) which is an antagonist of grey mold (Botrytis cinerea). The bees or bumblebees disseminate the spores and mycelium of the beneficial fungus to the flowers and so protect the flowers against grey mold.