Sugarcane veneer blotch
Narrow. Only known from Indonesia, Papua New Guinea, Philippines, and Solomon Islands.
The leaf spots are at first small, oval, light green to pale yellow, with thin red margins. Later, they become surrounded by a number (2-12) of progressively larger spots, each with a light green interior (turning light brown), and outlined by a 0.5-1 mm dark red border (Photo 1). The spots can reach 60 cm long by 1-1.5 cm wide. The spot has a veneer pattern, particularly on the upper surface, hence the name.
The underside of the leaf becomes black as the fungus forms spores.
Spread of the fungus is by airborne spores.
It is unlikely that this disease causes damage of economic value.
Look for the distinct oval spots that become successively surrounded by larger spots as they develop along the leaf blade or midrib.
This is a disease that is not well researched, but it seems likely that management is unnecessary as the damage caused is slight. It is more a curiosity, because of its unique symptoms, than one of economic interest.
AUTHOR Grahame Jackson
Photo 1 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.
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 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.