Bean Cercospora leaf spot, Cercospora leaf spot
Cercospora canescens. It is considered by some taxonomists to be identical with Cercospora apii (see Fact Sheet no. 136), and the same as Pseudocercospora cruenta (see Fact Sheet no. 303).
Worldwide. In the tropics and sub-tropics. Recorded from most countries in Oceania: American Samoa, Australia, Cook Islands, Federated States of Micronesia, Fiji, French Polynesia, Guam, Kiribati, Marshall Islands, New Caledonia, New Zealand, Niue, Palau, Papua New Guinea, Samoa, Solomon Islands, Tonga, Tuvalu, Vanuatu, and Wallis and Futuna.
Many members of the legume family (Fabaceae), including Calopogonium mucunoides, Crotalaria juncea, Desmodium tortuosum, Lablab purpureus, Macroptilium atropurpureum, Phaseolus lunatus (lima bean), Phaseolus vulgaris (French bean), Psophocarpus tetragonolobus (winged bean), Vigna marina, Vigna radiata (mung bean), Vigna unguiculata ssp. sesquipedalis (long bean), Vigna unguiculata ssp. unguiculata (cowpea). The host range will be wider if Cercospora apii is accepted as being the same as Cercospora canescens.
A fungal disease which affects mostly older leaves.
The spots start as small brown flecks, expanding to brown round to slightly angular spots with grey centres up to 1 cm diameter (Photos 1-3). The spots have reddish-brown margins, sometimes with yellow halos. The spots dry and pieces fall out giving a ragged look. The fungus also causes spots on the pods and grows inside them.
Spread is by spores in wind and rain. Survival between crops is on seed, and in crop debris. It may also survive on weeds.
A minor disease that is unlikely to affect yield. Usually, it occurs on the older dying leaves.
Look for the brown round to angular spots on the older leaves with greyish centres and darker margins, up to 1 cm diameter.
During plant growth:
There are less susceptible varieties of cowpea and mung bean.
Treat seed with thriam, captan or mancozeb. It is very unlikely that fungicides will be required to control this disease in the field; if they are required, use mancozeb or copper.
AUTHORS Grahame Jackson & Eric McKenzie
Information from Diseases of vegetable crops in Australia (2010). Editors, Denis Persley, Tony Cooke, Susan House. CSIRO Publishing. Photo 1-3 (taken by Eric McKenzie), and used in this fact sheet, appeared previously in McKenzie E (2013) Cercospora canescens PaDIL - (http://www.padil.gov.au).
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.
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