Initial symptoms usually begin at the neck, where affected tissue softens, becomes water-soaked, and turns brown. In a humid atmosphere, a gray feltlike growth appears on rotting scales and mycelia may develop between scales. Sclerotia may eventually develop in the neck and sometimes between scales. In garlic, symptoms appear either in the field towards the end of the season or during storage. Plants infected in the field may be stunted with dead and dying outer leaves.
Affected tissue is initially water-soaked but later turns dry and necrotic.
Sclerotia form in the neck or adhere to the rotten outer scales of the bulb. In both onion and garlic, initial infections may be latent and symptoms develop only when leaves senesce and become necrotic. The fungus persists on dead onion and garlic tissue and for long periods as sclerotia in the soil. The sclerotia germinate in moist weather and produce airborne conidia, which land on tissue, germinate, and infect when conditions are favorable. The fungus is associated with garlic and onions wherever they are grown and is a common colonizer of senescent tissue.