Photo 2. Purple blotch, Alternaria porri, on leaves of shallots showing zoned spots. Spores are produced in large numbers on these spots.
Photo 4. Purple blotch caused by Alternaria porri, on onion. The large spots are oval, purple and up to 150 mm long.
Onion purple blotch
AUTHOR Grahame Jackson
Information (and Photo 3) from Gerlach WWP (1988) Plant diseases of Western Samoa. Samoan German Crop Protection Project, Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) Gmbh, Germany; and from Diseases of vegetable crops in Australia (2010). Editors, Denis Persley, Tony Cooke, Susan House. CSIRO Publishing. Photo 2 Howard F. Schwartz, Colorado State University, Bugwood.org. Photos 3&5 Kohler F, Pellegrin F, Jackson G, McKenzie E (1997) Diseases of cultivated crops in Pacific Island countries. South Pacific Commission. Pirie Printers Pty Limited, Canberra, Australia. Photo 4 Howard F. Schwartz, Colorado State University, Bugwood.org.
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
This mini fact sheet is a part of the app Pacific Pests and Pathogens
The mobile application is available from the Google Play Store and Apple iTunes.