Plant pathogenic fungi are often attacked and suppressed by other fungi in the field. Those fungal antagonists that feed and thrive on or inside other living fungi, and damage them through specific adaptations to this specific lifestyle, are known as mycoparasites. Some mycoparasitic strains have already been developed as biocontrol agents of crop pathogenic fungi. Compared to plant-pathogen interactions, the interfungal parasitic relationships are much less studied and understood. We will present (a) the first comprehensive in silico analysis of genomic signatures of the mycoparasitic nutrition mode; (b) the first insights into genetic diversity of some common mycoparasites of powdery mildews and rusts, belonging to the genera Ampelomyces and Sphaerellopsis, respectively, and isolated in Australia; and (c) the first detailed genetic analysis of the interactions between powdery mildews and Ampelomyces mycoparasites based on transcriptomic and CRISPR-Cas studies.