''Podosphaera clandestina'' var. ''clandestina'' is a
plant pathogen
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomyc ...
that causes a
powdery mildew in apricots and peaches.
References
Fungal tree pathogens and diseases
Stone fruit tree diseases
clandestina var. clandestina
{{fungus-tree-disease-stub