Cordana leaf spot
Affecting bananas, cordana leaf spot (CLS), also known as banana diamond leaf spot, is caused by two fungi species; C. musae, which is more commonly found in tropical regions and C. johnstonii, which is found in the cooler banana growing regions of Australia. Although being widespread, CLS is not considered a major pest of bananas and is usually a secondary invader of leaf lesions caused by other fungi. Growth and spread of CLS can be accelerated by frequent rain and hot, humid conditions.
Description
Leaf spots (up to 10 cm), which are oval to diamond-shaped and pale brown with a yellow border, appear on the upper leaf side. Often spots merge, affecting large areas of the leaf, which turns brown and dries out. Spores are produced in large quantities on the underside of leaves, causing lesions to appear as greyish-brown and hairy. Dispersal of spores occurs via wet windy weather. Lesions caused by C.musae are generally larger and more elongated compared to C.johnstonii.
Plants are more susceptible to CLS under adverse environmental conditions (waterlogging or drought), nutritional deficiencies and injury or infection from other diseases, which provide an entry point for CLS to invade. Cavendish bananas appear to be more tolerant to CLS than native banana species (plantain).
Control
To reduce disease levels, infected leaves should be removed. Monitor plants for symptoms and when required apply a registered fungicide. Luna® Experience is registered for control of CLS. Scala® is registered for the control of CLS (C. musae).
References
Queensland Government (1998), ‘Tropical banana information kit’ Agrilink, pg 5, http://era.daf.qld.gov.au/id/eprint/1656/6/5protrbn_part1.pdfPestnet (Viewed Nov 2019), ‘Banana diamond leaf spot’, Pacific Pests and Pathogens fact sheet, http://www.pestnet.org/fact_sheets/banana_diamond_leaf_spot_072.htm
Vezina, A (2019), ‘Cordana leaf spot’, Pro Musa, http://www.promusa.org/tiki-print.php?q=%2FCordana+leaf+spot&page=Cordana+leaf+spot