Isolation and characterization of epiphytic fungi from the phyllosphere ofapple as potential biocontrol agents against apple scab (Venturia inaequalis)

From the phyllosphere of an apple orchard in North Germany ("Altes Land"), which had been transferred to management without pesticide treatments 10 ye ars ago, 107 epiphytic fungi were isolated within the season 1995. The obse rvation of a relatively high number of antagonistic interactions within the fungal community of this non-sprayed apple phylloplane suggested exploitat ion of natural antagonists for biological control of apple scab. This conce pt was further supported by che finding of 25 antagonists of the apple scab pathogen in an in vitro screening. Among them, six isolates of Auerobasidi um Botrytis, Cladosporium, Epicoccum and Fusarium inhibited mycelial growth or Venturia inaequalis (Coolie) G. Winter more than 80 % and conidial germ ination more than 50 %/. When applied to apple seedlings 24 h prior to inoc ulation with V. inaequalis, eight isolates effectively suppressed scab to a level comparable to the fungicide control. As these effective fungi of the class Hyphomycetes had no adverse effects on the plant, they are suggested as potential biocontrol agents against V. inaequalis in its biotrophic pha se.