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Recent reports of plant diseases that result in yield reduction and increasing demand for dragon fruits raise concerns of fruit supply shortage. Emerging plant diseases may play an important role in increasing yield losses and reducing the availability of stem cuttings (source of planting materials). Understanding the aetiology of current and new diseases of dragon fruit is important to address production issues and to formulate effective disease control measures. This study reports Epicoccum sorghinum as a potential emerging pathogen of dragon fruit. Epicoccum sorghinum MBDF0024a was isolated from dragon fruit stems (Hylocereus monacanthus) showing brown spot symptoms. DNA sequence of the internal transcribed spacer (ITS‐rDNA), beta tubulin and actin gene regions of fungal isolate MBDF0024a had high similarities to E. sorghinum stains. Epicoccum sorghinum MBDF0024a was pathogenic to three cultivated dragon fruit species (Hylocereus undatus, H. monacanthus and H. megalanthus) in repeated laboratory and glasshouse trials. Large brown lesions developed on 3‐week‐old inoculated rooted stem cuttings 3 days postinoculation (dpi). Yellowing of the lesion (advance part) started at five dpi, and at seven dpi, yellowing was observed in the stem. As there are no reported control measures for diseases caused by E. sorghinum, this study screened chemicals with antifungal properties. A biopesticide containing B. subtilis (2 ml/400 ml), and chemicals isoprothiolane (2.25 ml/400 ml), mancozeb (2 g/400 ml) and pyraclostrobin (1 ml/400 ml) (chemical control) completely inhibited the in vitro growth of E. sorghinum MBDF0024a. The results establish E. sorghinum as a new and emerging pathogen of dragon fruit that could be a major yield‐limiting disease if left uncontrolled. The biopesticide can be considered a fairly safe option for disease management, but glasshouse and field studies are needed for validation.

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Diseases are among the major problems that negatively affect dragon fruit profitability worldwide. Diseases of dragon fruit in the Philippines are yet to be identified and reported. This study elucidates the causal agent of a disease infecting stems of dragon fruit grown in Los Baños, Laguna, Philippines. The fungus was isolated and identified as Nigrospora sp. based on morphological and cultural characteristics in potato dextrose agar medium. Using the DNA sequence of the internal transcribed spacer (ITS) gene region, isolate MBDF0016b was identified as Nigrospora sphaerica. The Philippines strain was closely related to the Malaysian strain, which also causes reddish-brown spot in dragon fruit (H. polyrhizus), and to other N. sphaerica isolates from other host-plant species. Nigrospora sphaerica MBDF0016b was pathogenic to H. megalanthus, H. undatus, and H. polyrhizus in detached stem and glasshouse assays. The same fungus was re-isolated from the inoculated stems and thus, establishing Koch’s postulate. This paper is the first confirmed scientific record of a dragon fruit disease in the Philippines and the first report of N. sphaerica as a dragon fruit pathogen causing reddishbrown spot disease in H. megalanthus.