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Botrytis, Downy Mildew and Purple Blotch of Onion

Howard Schwartz (March, 2013)

Summary

Neck rot, gray mold, or leaf and flower blast of onions and garlic is caused by various species of the fungus botrytisincluding B. allii, B. byssoidea, and B. squamosa. Botrytis cinerea can infect onion seed heads and cause brown stain. This fact sheet describes the pathogens, their symptoms and methods of control.