The biocontrol agent Myco-Sin is used as plant health enhancer for fire blight control in ecological fruit growing. Using two in-vivo-systems indications for the mechanism of action of Myco-Sin were found. Myco-Sin clearly reduced the development of fire blight symptoms on detached pear blossoms, because the growth of Erwinia amylovora on stigmas and hypanthia was inhibited. With a pathogenicity test on immature pear fruits the resistance inducing effect of Myco-Sin was confirmed
