Onion Disorder: Purple Blotch

SKU A3804

Author(s) Karen Delahaut, Walt Stevenson.

Purple blotch causes onion leaves to become blighted and die prematurely. The result is reduced yields from undersized and immature bulbs. In storage, diseased bulbs rot.

This disorder affects onions, garlic, leeks, and false shallot. The fungus that causes purple blotch (Alternaria porri) is closely related to the species that causes early blight on tomatoes and potatoes (Alternaria solani). This fact sheet will help you identify, prevent, and control purple blotch on onions and related crops in your home garden (2 pages; 2004).