Little is known regarding the fungi, especially fungal pathogens, associated with mangroves in Africa. This includes fungi in the Botryosphaeriaceae that comprise numerous opportunistic, stress-associated pathogens often associated with trees affected by environmental and anthropogenically generated stresses, such as those affecting mangroves. We investigated the occurrence of endophytic Botryosphaeriaceae along the entire distribution of mangroves in South Africa. Asymptomatic branches were collected from ten localities and six mangrove species. Isolates resembling species of Botryosphaeriaceae were identified based on multi-gene sequence data of the internal transcribed spacer regions (ITS), including the 5.8S nrRNA, the beta-tubulin (tub2), partial translation elongation factor 1-alpha (tef1-α), and DNA-directed RNA polymerase II second largest subunit (rpb2) gene regions. Inoculation trials were conducted on healthy branches of Avicennia marina and Bruguiera gymnorrhiza to evaluate the potential pathogenicity of the collected species. Fourteen species in the Botryosphaeriaceae belonging to four genera, Botryosphaeria, Diplodia, Lasiodiplodia, and Neofusicoccum were collected, including five new species. Neofusicoccum was the most prevalent genus followed by Lasiodiplodia, with species of Diplodia and Botryosphaeria being the least frequent. The inoculation studies revealed that one of the new species, Lasiodiplodia avicenniae is highly pathogenic to A. marina and could pose a threat to the health of these trees.

Mangroves are critically important components of coastal ecosystems. However, their survival is globally threatened, mostly due to impacts resulting from human activities. Reports of mangrove deaths associated with pathogens and insect pests have emerged during the past few years. In South Africa, mangrove species are under pressure from both environmental and anthropogenic disturbances, potentially making them more susceptible to diseases. We present the most detailed evaluation of possible biotic causes of mangrove decline in South Africa to date. Surveys covering the entire distribution range of mangroves in the country were conducted. Qualitative and quantitative data from siltation of pneumatophores, stand density, diameter at breast height and the presence of wood-boring beetles were correlated with disease incidence and severity to elucidate the possible relationships with mangrove health. Phylogenetic analyses were performed to determine the taxonomic placement of fungi isolated from symptomatic trees. Of five true mangrove species and two mangrove associates examined, only Avicennia marina showed signs and symptoms of branch and stem cankers, die-back, wood-boring insects and leaf galls. Barringtonia racemosa showed symptoms of fruit and leaf disease and Hibiscus tiliaceus was observed with herbivory by leaf-feeding beetles. Using a multivariate approach, the presence of beetles and high pneumatophore siltation appeared to be associated with the observed die-back and canker levels of A. marina. Four main fungal groups were recovered from symptomatic trees. The results suggest that natural and anthropogenic stressors exerted on the mangrove trees lead to the colonization of an array of opportunistic pests and diseases.

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Mangrove trees are continuously under stress due to environmental and/or anthropogenic pressures, which expose them to attack by pathogens, compromising their survival.Ophiostomatoid fungi cause sap stain and diseases of a wide spectrum of tree species globally. These fungi infect trees through natural, insect, animal and/or human made wounds.During routine surveys of mangrove trees in South Africa, wounds on branches and stems of Avicennia marina were regularly monitored for the presence of ophiostomatoid fungi at ten study sites in the country. The stems of four mangrove species, Avicennia marina, Bruguiera gymnorrhiza, Rhizophora mucronata and Barringtonia racemosa were also wounded and evaluated for the appearance of these fungi. Ophiostomatoid fungi were obtained from the mangrove associate B. racemosa, but not from any of the true mangroves. Analyses of DNA sequence data for the Internal Transcribed Spacer (ITS), β-tubulin (BT), Calmodulin (CAL) and Translation Elongation Factor (TEF) gene regions revealed that the fungi isolated from the wounds on B. racemosa belong to three species in the Ophiostomataceae, including a new taxon described here as Ophiostoma palustre sp. nov. Results suggest that the mangrove associate B. racemosa is more prone to colonization by ophiostomatoid fungi than the true mangroves.

Barringtonia racemosa (Lecythidaceae) is a widely distributed mangrove associate in coastal areas of Africa, Asia and Australia. During routine disease surveys along the east coast of the KwaZulu-Natal Province in South Africa, B. racemosa trees were observed showing symptoms of leaf infection and necrotic lesions on fruits. A previously undescribed species of Pseudocercospora was commonly associated with these symptoms. 1 This fungus is described as Pseudocercospora mapelanensis sp. nov., based on multi-gene sequence analyses of the ACT, ITS, LSU and TEF genome regions, as well as morphological characteristics.