USE OF HONEYBEES (APIS MELLIFERA) AS VECTORS FOR FIRE BLIGHT ANTAGONISTS IN FIELD EXPERIMENTS

Fire blight is a serious disease in pome fruits. The use of antagonistic microorganisms for fire blight control is one of several methods under discussion. Besides spraying, flower visiting insects (e.g., honeybees) could be used as vectors to carry antagonists onto host plant blossoms. During two seasons, dispersal of Aureobasidium pullulans, the microbial active ingredient of "Blossom Protect^™", using honeybees as vectors, was investigated in field trials in Austria. Hive mounted dispensers were filled with a powdered formulation of A. pullulans strains CF10 and CF40. By passing the dispensers, bees brought antagonists continuously from hives to host plants in the orchards. Outgoing bees from dispenser colonies had higher A. pullulans loads per bee than incoming or house bees. The use of specific SCAR primers made it possible to confirm the successful transmission of the product strains from the hive mounted dispensers to apple and pear blossoms. In an orchard of 16 hectares, ten bee colonies with adjusted product dispensers – subdivided in two beeyards, were sufficient to supply 50% of apple and 62% of pear blossoms with A. pullulans strains CF10 and CF40. It is concluded that this type of application is a possible way to reduce the pressure of E. amylovora infections to pome fruits as well as to other host plants.