Using DNA sequencing and morphological identification, we have established that a species of Pestalotiopsis could be the culprit behind the lesions. While a handful of different species of Pestalotiopsis have been identified on Red Mangroves in Florida, Bermuda, and China, most of these documentations identified species as saprobes (the fungus lives on decaying material) or endophytes (the fungus lives inside the host plant). Interestingly, Pestalotiopsis is a genus of fungi that can be pathogenic, live as endophytes, or as a saprobes.
While this information is exciting, it does not mean that we definitively found the causal fungus of the lesions. In order to explicitly determine this, we will infect non-diseased Red Mangrove leaves we have been growing here at NC State to see if the spores from Pestalotiopsis elicit the same lesions we find in the field on Abaco. We will begin infections over the next week or so. Check back for updates!
Maharachchikumbura, S. N., L.-D. Guo, E. Chukeatirote, A. Bahkali, and K. Hyde. 2011. Pestalotiopsis—morphology, phylogeny, biochemistry and diversity. Fungal Diversity 50:167-187.