Fire blight control in organic fruit growing – systematic investigation of the mode of action of potential control agents

Summary in the original language of the document

Effective control agents are needed to prevent blossom infections by the fire blight pathogen Erwinia amylovora in organic fruit growing. In this study 18 preparations of potential control agents were compared for their efficiency against E. amylovora. In shaken cultures twelve control agents inhibited the growth of E. amylovora completely. In this system different mechanisms of action were found. Six control agents shifted the pH of the cultures to values not suitable for bacterial growth (<5 or >8). Three agents act by copper, a known bactericide. The control agent Elot-Vis has high ethanol content, which was responsible for the high efficiency in vitro. On detached apple blossoms only four control agents led to a symptom reduction of more than 50%. Only two of them (Blossom-Protect fb, BPASc) exhibited a high efficiency in field trials. Our results suggest that the control agents, which led to a high efficiency in shaken cultures, are not sufficient for good performance in the field.