Grapevine powdery mildew is a key disease all across Europe and is currently controlled
almost exclusively using fungicides. To develop a new biofungicide product against this disease, caused
by Erysiphe necator, a large culture collection of Ampelomyces strains collected worldwide from
different powdery mildew species was screened to assess for the first time the level of variability of
different characteristics of these biocontrol agents known to occur as natural mycoparasites of powdery
mildews in the field. This preliminary screening revealed a considerable diversity in many characteristics
of different Ampelomyces strains including both culture patterns and mycoparasitic activities against the
asexual and sexual stages of E. necator. The screening protocol developed in this work could be used in
further studies on Ampelomyces in order to develop new effective commercial biofungicide products
against powdery mildew infections of grapevine and other crops