Natural occurrence of the mycoparasite Ampelomyces quisqualis (Ascomycota, Phaeosphaeriaceae) in urban environments from Tucumán (Argentina)

Platanus × acerifolia is used as an urban shade tree in many cities throughout Argentina. In late autumn and winter of 2023, leaves and fruits of P. × acerifolia showing typical symptoms of a powdery mildew were collected along the main streets of Tucumán, Argentina. Its morphology and comparison with published descriptions allowed us to identify the fungus as the asexual morph of Erysiphe platani. The specimens were heavily hyperparasitized by Ampelomyces quisqualis, a mycoparasitic ascomycete, used as a natural biological control of the development of powdery mildew species. This work reports the natural occurrence of Ampelomyces in urban environments in Argentina. The disease symptoms and morphological characteristics of the powdery mildew anamorph and the mycoparasite are described and illustrated.