First report of alternaria leaf spot of banana caused by Alternaria alternata in the United States.
Research efforts were initiated in 2003 to identify and introduce banana (Musa spp.) cultivars suitable for production in Georgia (GA), USA. Selected cultivars have been evaluated since 2009 in Tifton Banana Garden, Tifton, GA, comprising cold hardy, short cycle, and ornamental types. In spring and summer 2012, seven out of 13 cultivars (African Red, Blue Torres Island, Cacambou, Chinese Cavendish, Novaria, Raja Puri, and Veinte Cohol) showed tiny, oval (0.5 to 1.0 mm long and 0.3 to 0.9 mm wide), light to dark brown spots on the adaxial surface of the leaves. Spots were more concentrated along the midrib than the rest of the leaf and occurred on all except the newly emerged leaves. Leaf spots did not expand much in size, but the numbers approximately doubled during the season. Disease incidences on the seven cultivars ranged from 10 to 63% (10% on Blue Torres Island and 63% on Novaria), with an average of 35% when a total of 52 plants were evaluated. Based on morphological characteristics, sequence analysis of the rDNA internal transcribed spacer region and pathogenicity assay, the causal agent was identified as Alternaria alternata. This is thought to be the first report of Alternaria leaf spot caused by A. alternata on banana in the United States.