They infect and feed on the plant via haustoria. Secondary infection is caused by the production and dispersal of conidia (asexual spores). Chasmothecium are then produced on vegetative surface of host in late summer.
The process of fungal infection involves invasion and nutrient uptake via haustoria, as well as secondary infections triggered by conidial release and dispersal. In late summer, chasmothecium form on the plant's surface.