Recent research has suggested that increasing neighbourhood tree species diversity may mitigate the impact of pests or pathogens by supporting the activities of their natural enemies and/or reducing the density of available hosts. In this study. we attempted to assess these mechanisms in a multitrophic study system of young oak (Quercus). oak powdery mildew (PM. https://www.parisnaturalfoodes.shop/product-category/ultimate-flora/